Title:
Heat exchanger, method of manufacture and tube plate therefor
Kind Code:
A1


Abstract:
This invention relates to a heat exchanger, to a method of manufacturing the heat exchanger, and to a tube plate for use in the heat exchanger. The heat exchanger is particularly suited for radiators for motor vehicles. The heat exchanger comprises an array of tubes, at least one end of each tube being sealingly connected to a tube plate, the tube plate having a first tube plate wall and a second tube plate wall with a gap between the tube plate walls, each of the first tube plate wall and the second tube plate wall having an opening to receive the end of a tube, the gap between the tube plate walls providing a chamber for containing a sealing material. There is also provided a method of making a heat exchanger including the step is injecting a settable sealing material into the chamber defined by the tube plate walls.



Inventors:
Pierce, David Bland (Warwick, GB)
Evans, David Eric (Bromsgrove, GB)
Application Number:
10/515947
Publication Date:
08/18/2005
Filing Date:
08/19/2004
Assignee:
PIERCE DAVID B.
EVANS DAVID E.
Primary Class:
International Classes:
F28D1/053; F28F9/02; F28F9/16; (IPC1-7): F28F9/04
View Patent Images:
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Primary Examiner:
WALBERG, TERESA J
Attorney, Agent or Firm:
PEDERSEN & COMPANY, PLLC (BOISE, ID, US)
Claims:
1. A heat exchanger comprising an array of tubes, at least one end of each tube being sealingly connected to a tube plate, the tube plate having a first tube plate wall and a second tube plate wall with a gap between the tube plate walls, each of the first tube plate wall and the second tube plate wall having an opening to receive the end of a tube, the gap between the tube plate walls providing a chamber for containing a sealing material.

2. A heat exchanger according to claim 1 wherein the tube plate is part of a header.

3. A heat exchanger according to claim 1 wherein the tube plate is formed as an extrusion.

4. A heat exchanger according to claim 1 wherein there is an interference fit between the tube ends and the tube plate openings.

5. A heat exchanger according to claim 1 wherein the chamber has a first hole for the injection of the sealing material.

6. A heat exchanger according to claim 5 wherein the chamber has a second hole to allow the escape of air during injection and the escape of sealing material when the chamber has been filled with sealing material.

7. A heat exchanger according to claim 1 wherein the tube carries a number of extended surface members, and wherein the end-most extended surface member engages the first tube plate wall.

8. A heat exchanger according to claim 1 comprising two headers, a number of tubes sealingly connected to both headers, and a number of extended surface members carried by each of the tubes, each header having a respective tube plate, wherein the headers, including the tube plates, the tube(s) and the extended surface member(s) are of aluminium.

9. A heat exchanger according to claim 1 wherein the first tube plate wall is manufactured separately from the second tube plate wall.

10. A heat exchanger according to claim 1 wherein the sealing material is two-pack silicon elastomer.

11. A tube plate for use in a heat exchanger, the tube plate having a first tube plate wall and a second tube plate wall with a gap between the tube plate walls, each of the first tube plate wall and the second tube plate wall having an opening to receive the end of a tube, the gap between the tube plate walls providing a chamber for containing a sealing material.

12. A method of assembling a heat exchanger, the heat exchanger comprising an array of tubes, an end of each tube being sealingly connected to a tube plate, the tube plate having a first tube plate wall and a second tube plate wall, there being a gap between the tube plate walls defining at least one chamber of the tube plate, each of the first tube plate wall and the second tube plate wall having an opening to receive an end of a tube, the method including the steps of {i} inserting an end of each tube into respective openings in the first and second tube plate walls, the end of each tube passing through the chamber, {ii} providing an injection opening in the chamber, {iii} injecting a settable sealing material into the chamber through the respective injection opening, and {iv} allowing the sealing material to set so as to seal the end(s) of the tube(s) in the tube plate.

13. A method according to claim 12 wherein the tubes are fitted with extended surface members as a preliminary assembly step.

14. A method according to claim 12 including a control step of comparing the actual volume of settable sealing liquid injected against the expected volume in order to check for leaks.

15. A method according to claim 12 wherein the settable sealing material is liquid rubber.

Description:

FIELD OF THE INVENTION

This invention relates to a heat exchanger, to a method of manufacturing the heat exchanger, and to a tube plate for the heat exchanger. The invention is expected to find its greatest utility in heat exchangers for use as radiators for motor vehicles, and so much of the following description will relate to such use. However, use of the invention in other applications is not thereby excluded.

BACKGROUND OF THE INVENTION

Often it is necessary to cool a working fluid, and it is known for this purpose to use a heat exchanger. Many different forms of heat exchanger are known, suited to the particular application, but most utilise a number of tubes formed of a heat conductive material, with one fluid (usually the working fluid) flowing within the tubes, and the other fluid (usually the coolant) flowing therearound. Heat is exchanged between the working fluid and the coolant by way of the walls of the tubes, the coolant being heated up as the working fluid is cooled.

The tubes are typically connected to header tanks, the header tanks acting as manifolds for the working fluid prior to and after passage through the tubes.

In a radiator for a motor vehicle, the working fluid is typically a water-based fluid which circulates around the engine where it absorbs heat and subsequently through the radiator where it gives up the absorbed heat. However, certain motor vehicles also utilise an oil cooler where the working fluid is engine oil, and an air cooler where the working fluid is air which has been compressed by a supercharger or turbocharger prior to introduction into the engine. In all cases, the coolant is air at substantially ambient temperature, the working fluid giving up heat to the air as this passes through or around the radiator.

To increase the thermal transfer, the tubes will typically carry metallic extended surface members or fins which are in thermal contact with the tubes and act to increase the available surface area in contact with the air and increase the rate of heat transfer from the working fluid.

Aluminium is a common material from which the tubes, fins and headers are constructed as it has good heat conductivity, is relatively cheap and is easy to form and machine.

It is a characteristic of the water, oil and air coolant systems in motor vehicles that the maximum pressure of the working fluid which the radiator and other components must accommodate is relatively low, for example around 2×105 Pa (approximately twice atmospheric pressure).

DESCRIPTION OF THE PRIOR ART

Several different designs of radiator are utilised in modern motor vehicles, but the majority fall into two broad classes. The first class comprises radiators in which the tubes are brazed to the headers and also to the fins. The second class comprises radiators in which the tubes are mechanically expanded into thermal engagement with the fins and into sealing engagement with the headers.

Radiators in both of these classes suffer from major drawbacks. The requirement to braze radiators in the first class adds to the cost and complexity of these radiators, and the time taken to manufacture them. In addition, if some of the brazing is not completed correctly one or more of the fins may migrate relative to the tubes in service, reducing the rate of thermal transfer. More seriously, if the deficient brazing is between a tube and header the radiator may leak. The deficiency may not manifest itself until the radiator is in service and undergoes the vibrations typically experienced in use. In addition, the requirement to braze the components together limits the materials from which the radiator may be constructed, so that different materials which may be more suited for use in a particular radiator cannot be used.

A patent describing a method of making a radiator in the second class is U.S. Pat. No. 4,570,317. This patent describes a method of expanding elliptically-shaped tubes into engagement with the fins, elliptically-shaped tubes being commonplace in these applications since they generally provide better heat exchange for a given rate of air flow through the radiator than circular tubes, for example.

U.S. Pat. No. 4,570,317 describes a method of connecting the tube to each of the fins, but it does not describe a method of sealing the tubes to the headers. To provide this seal, one known method is to utilise a header comprising an aluminium tube plate, the tube plate carrying a resilient and flexible sealing sheet. The sealing sheet covers the tube plate and has openings corresponding to the openings in the tube plate, and which openings will subsequently receive an end of a respective tube. The sealing sheet includes collars which lie within the openings of the tube plate. When the tubes are subsequently introduced into the tube plate they are sized to fit into the collars of the sealing sheet, so that the collars lie between the tubes and the respective openings in the tube plate, and prevent direct contact between the aluminium tubes and the aluminium tube plate. The ends of the tubes are then mechanically expanded to compress the collars of the sealing sheet and form a seal between the tube plate and the tubes.

To enable mechanical expansion of the tubes access is required to the end of the tubes after they have been fitted to the tube plate, so that the remainder of the header is necessarily separate from the tube plate, and may be secured thereto as a final step of the assembly process.

One disadvantage of this type of radiator is the number of different materials from which it is made. A least two different materials are required, and three if the remainder of the header is of plastic material as is typically the case. The use of a number of different materials makes recycling of the radiator difficult and expensive. Also, even with complex and expensive machinery with which to assemble the radiator it still takes around four minutes to assemble the radiator, and it is desired to reduce the assembly time so as to reduce the cost thereof.

A machine and method for adding extended surface members to the tubes of a heat exchanger is described in each of published patent applications WO96/35093 and WO02/30591. Each of these applications provides an improvement to the “brazing” and “mechanically expanding” methods for applying the fins to the tubes. It is expected that a “fin block” comprising an array of tubes to which the fins have been fitted will be a preliminary step in utilising the method according to the present invention, as this is usually a preliminary step in manufacturing the second class of radiators described above. The present invention is primarily directed to the subsequent step of assembling the fin block into the heat exchanger. The method could utilise a fin block constructed according to U.S. Pat. No. 4,570,317 or the like, but will preferably utilise a fin block constructed according to one of WO96/35093 and WO02/30591.

SUMMARY OF THE INVENTION

It is an object of the present invention to reduce or avoid the problems associated with the known radiators described above.

According to the invention therefore, there is provided a heat exchanger comprising an array of tubes carrying extended surface members, each end of each tube being sealingly connected to a tube plate, the tube plate having a first tube plate wall and a second tube plate wall with a gap between the tube plate walls, each of the first tube plate wall and the second tube plate wall having an opening to receive the end of a tube, the gap between the tube plate walls providing a chamber for containing a sealing material.

There is also provided a method of assembling a heat exchanger, the heat exchanger comprising an array of tubes carrying extended surface members, each end of each tube being sealingly connected to a tube plate, the tube plate having a first tube plate wall and a second tube plate wall, there being a gap between the tube plate walls defining at least one chamber of the tube plate, each of the first tube plate wall and the second tube plate wall having an opening to receive an end of a tube, the method including the steps of {i} inserting an end of each tube into respective openings in the first and second tube plate walls, the end of each tube passing through the or a chamber, {ii} providing an injection opening in the or each chamber, {iii} injecting a settable sealing liquid into the or each chamber through the respective injection opening, and {iv} allowing the sealing liquid to set so as to seal the end(s) of the tube(s) in the tube plate.

The tube plate can be a part of the header, there usually being two headers in a heat exchanger, or it can be an intermediate support plate lying between the headers.

Desirably, the tubes are fitted with extended surface members as a preliminary assembly step, so that a fin block is presented to the tube plate in step {i} of the method described above. In such embodiments, the end-most extended surface member can abut the tube plate so as to facilitate ease of assembly, i.e. the position of the end-most extended surface member can be predetermined to allow sufficient unfinned length of tube to enter the openings in both of the first and second tube plate walls. Allowing the tube plate to abut the end-most fin avoids the requirement for fixing jigs to accurately and securely hold the tube plate relative to the tubes during injection and setting of the sealing liquid. With the machines and methods of WO96/35093 and WO02/30591 the positions of each extended surface member can be strictly controlled.

In embodiments in which the tube plate is a part of the header, the header may be constructed in one piece. Thus, since it is not necessary to access the tube ends after their insertion into the tube plate the header is not required to be constructed from several separable parts.

Desirably, the header is an extrusion, preferably of aluminium. Thus, it will be understood that the header can be extruded and then cut to length, with suitable end plates to close off the open ends of the extrusion. A single form of header extrusion can be used for different-sized radiators, the radiators differing only in the length of the extrusion and the corresponding number of tubes fitted thereto.

The tubes can be of circular, elliptical or other chosen cross-sectional shape. The openings in the tube plate walls should be of a size and shape, and be positioned, corresponding to the tubes in the array. However, since no expansion of the tube ends occurs it is preferred that the tube ends be a close (or interference) fit into the openings. It does not matter if none of the sealing liquid permeates into the gap between the tube end and an opening in a tube plate wall since a complete seal will be formed within the chamber.

The fit between the tube ends and the tube plate openings should be sufficiently small to prevent or limit the amount of sealing liquid that will pass therebetween so as to avoid wastage of the sealing liquid, and possible inadequate sealing across the whole tube plate. Thus, desirably the tube plate will have a first hole as an injection opening, and a second hole to allow the escape of air during filling and to act as a fill opening, the sealing liquid being injected into the injection opening from bottom to top so that it fills up the chamber and completely surrounds all of the tube ends therein before escaping through the fill hole. The manufacturer can stop injecting further liquid once it starts escaping from the fill hole. If a significant quantity of sealing liquid escapes into the header or between the tubes and fins then more will be required to cause the escape through the fill hole, and the level in the chamber may subsequently drop before the liquid has set, exposing some of the tube ends within the chamber and leaving them improperly sealed.

Clearly, any leakage of sealing liquid can be determined even if this is not observable since the volume of sealing liquid which should be required in the absence of leakage can readily be calculated or measured and the method can include the control step of checking for leaks by comparing the actual volume injected against the expected volume.

Any leakage of sealing liquid which might occur through the first tube plate wall (adjacent the extended surface members) will be minimised if (as is desired) the end-most extended surface member engages that tube plate wall.

The presently preferred sealing material is two-pack silicon elastomer which is available in liquid form and which can readily set at ambient temperature. Other suitable materials could alternatively be used such as liquid rubber or settable adhesives or the like, provided that they form a suitable seal at the pressures and temperatures involved in use of the heat exchanger.

It will be understood that the fin block comprising the tubes and extended surface members may be all aluminium, and so may be the header (and support plate if provided), so that only two materials are required for the heat exchanger, namely aluminium and the sealing material. The sealing material may be arranged to break down under certain thermal and/or chemical conditions (it being ensured that these conditions will not exist during use, but only when the heat exchanger is to be recycled), so that recycling of a vehicle radiator for example made according to the present invention is made significantly easier than with the prior art radiators.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic representation of a prior art radiator for a motor vehicle;

FIG. 2 shows an end view of the header of a heat exchanger according to the present invention;

FIG. 3 shows a front view of part of a heat exchanger according to the present invention;

FIG. 4 shows a perspective view of part of another embodiment of heat exchanger;

FIG. 5 is a side sectional view of another embodiment of tube plate according to the invention, in use as a support plate to interconnect first and second heat exchanger tubes;

FIG. 6 is a perspective view of part of an assembled heat exchanger having a tube plate similar to that of FIG. 5;

FIG. 7 is an end view of an alternative embodiment of tube plate for use as a support plate;

FIG. 8 is an end view of a header of a heat exchanger utilising a further alternative embodiment of tube plate, during assembly of the tube plate and header; and,

FIG. 9 is a view as FIG. 8 of the assembled header.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The prior art radiator 10 shown in FIG. 1 has certain constituent parts which are common to most motor vehicle radiators, and which are also common to preferred embodiments of heat exchangers according to the present invention. Specifically, the radiator 10 comprises two headers 12, 14 which are joined together by way of several tubes 16, the tubes carrying a number of extended surface members or fins 20. For clarity, in this drawing only seven tubes are shown, and only ten fins, but in practice the number and density of the tubes and fins will be far greater.

Each header 12, 14 has a respective tube plate 26 which has openings (not seen) to receive the ends of the tubes 16, the ends of the tubes 16 being sealed to the tube plates 26 by known means.

The header 12 has an inlet 22 and the header 14 has an outlet 24, the inlet 22 and the outlet 24 being connected to a circuit for the working fluid (in this case water) so that the water circulates around the engine (not shown) where it acquires heat, and then through the radiator where it gives up that heat in known fashion.

FIG. 2 shows a header 30 according to the present invention which can be used in place of the headers 12 and 14 in a radiator 10 of a motor vehicle. According to the invention, the tube plate of the header 30 comprises a first tube plate wall 32 and a second tube plate wall 34. Each of the tube plate walls 32, 34 has openings 36 formed therein to receive the ends of the tubes 16.

In this embodiment there are two sets of openings 36, so that the header 30 can accommodate two rows of tubes 16. In other embodiments there are one, three or more sets of openings to accommodate one, three or more rows of tubes, respectively (the heat exchanger of FIG. 4 has four rows of tubes, for example). Also, in this embodiment the tube plate includes a strengthening rib 40 joining the approximate centre-lines of the first tube plate wall 32 and the second tube plate wall 34. It is expected that a header with a larger number of sets of openings 36 will require more strenghtening ribs, but as shown in the embodiment of FIG. 4 it is not essential that a strengthening rib lie between each set of openings.

The tube plate of this embodiment provides two chambers 42, 44 which are substantially identical.

When assembling a heat exchanger according to the invention the tubes 16 and fins 20 are preferably assembled together as a preliminary manufacturing step, desirably utilising the machine and method of one or other of WO96/35093 and WO02/30591. Thus, it is preferably arranged that the fins 20 contact all of the tubes 16 in the array so that the fins and tubes together comprise a fin block, i.e. a complete unit for fitment to the headers 30.

The fin block is presented to the headers 30 (one at each end of the tubes 16), with the tubes 16 aligned with the openings 36. The tubes 16 are inserted into the respective openings so that the ends of the tubes pass through both the first tube plate wall 32 and the second tube plate wall 34, as shown in FIG. 3 (though it is not necessary that the tubes extend beyond the second tube plate wall 34 as shown in that figure).

It is desired that the tubes 16 be a close or interference fit into the openings 36, for the reason explained below.

The tubes 16 are preferably inserted into the openings 36 until the end-most fin 20 engages the first tube plate wall 32 (see FIG. 3, which shows only the end-most fin 20). Since the assembly of the fin block using a machine and method according to one or other of WO96/35093 and WO02/30591 can be closely controlled, it can be arranged that the end-most fin 20 on each end of the fin block is positioned so that the respective headers 30 are correctly positioned when the first tube plate wall 32 of each header 30 engages those end-most fins. It will be understood that in such embodiments the end-most fins serve primarily as locations for the headers and their role in dissipating heat is secondary.

As will be observed from FIG. 3, the ends of the header 30 are closed by end-plates 46 and 50 respectively, the end-plate 50 including a conduit 52 which can provide the inlet or outlet to the heat exchanger similar to the inlet 22 or the outlet 24 of the heat exchanger 10 of FIG. 1. It will be understood that the end-plates 46 and 50 are substantially flat, and are fixed in a leak-tight manner to the ends of the extrusion 54. Thus, the cross-sectional form of the header 30 shown in FIG. 2 comprises an extruded form 54, and different capacity heat exchangers can be manufactured by varying the length of extrusion used, and therefore varying the number of tubes used in the heat exchanger.

The cross-section of FIG. 3 shows the chamber 42, though it will be understood that the cross-section for the chamber 44 will be substantially identical. Since it is part of the extrusion 54 the chamber 42 runs the full length of the header 30, and terminates at the end-plates 46 and 50. Each end-plate 46 and 50 includes a hole, the hole in the end-plate 46 comprising an injection hole 56, the hole in the end-plate 50 comprising a fill hole 60 (though the purpose of these holes could be reversed if desired).

When the fin block has been assembed to the header 30, the heat exchanger is laid on its end so that the end-plates 46, 50 are substantially horizontal with injection hole 56 below the fill hole 60. A settable sealing liquid is then injected into the injection hole 56, which fills up the chamber 42 and eventually escapes from the fill hole 60. When sealing liquid starts escaping from the fill hole 60 injection is stopped, and the sealing liquid is allowed to set into a solid sealing material around each of the tubes in the chamber 42.

It is preferred that the sealing material is injected in such a way that bubbles of air or other gas do not enter or remain therein, which bubbles may affect the seal which can be provided when the liquid sets. However, the present invention does not exclude the use of a foaming material as the sealing liquid, provided that the foam is of a closed-cell structure suited to sealing applications at the pressures and temperatures involved.

The injection process is repeated for each of the chambers in each of the headers until all of the chambers 42, 44 (etc.) have been filled with sealing liquid, and that liquid has been allowed to set.

A perspective view, partly cut away, of an assembled heat exchanger is shown in FIG. 4. The sealing liquid has set into a solid (but flexible) sealing material 62 which fills the chambers between the tube plate walls 32 and 34 and surrounds the end of each of the tubes 16, so as to prevent the passage of working fluid from within the header past the first and second tube plate walls 32 and 34.

It will be understood that some of the sealing liquid may encroach into the gap between a tube 16 and an opening 36 in a tube plate wall during or after injection, but provided that the volume of liquid so encroaching is small that will not prevent effective sealing. Sealing will only be jeopardised if sufficient sealing liquid leaks so that some of the tubes are no longer surrounded with sealing liquid before this sets. Such an extreme leak could readily be determined, however, since the volume of the chamber 42 can readily be measured or calculated, and the injection of a greater volume of sealing liquid before the liquid begins to escape from the fill opening 60 will indicate a leak past one or both of the first tube plate wall 32 and the second tube plate wall 34.

In this regard, it will be understood that engagement of the end-most fin 20 with the first tube plate wall 32 will reduce the leakage that can occur past the first tube plate wall 32.

The embodiment of FIG. 4 has four rows of tubes 16, and two strengthening ribs 40, and is suited for a larger vehicle such as a truck or bus. Smaller embodiments such as that of FIG. 2 would be suitable for smaller vehicles such as cars. In the embodiment of FIG. 4 the tubes 16 are of circular cross-section, though that is not necessary, and the tubes could be elliptical or other suitable shape. In particular, since mechanical expansion of the tubes is not required for the present invention (or for the application of the machine and method of one or other of WO96/35093 and WO02/30591), the cross-sectional shape of the tubes can be whatever is desired, and in particular can be a shape most suited to heat exchange and not constrained by the method of assembling the heat exchanger.

As indicated above, whilst the invention has been primarily designed with radiators for motor vehicles in mind, it could equally-well be used in other heat exchanger applications. One other suitable application would be in “shell and tube” (or cylindrical) heat exchangers. The invention may also be used in the evaporator and/or condenser of refrigeration units where the working fluid is a refrigerant. In the latter applications the pressure of the working fluid is relatively low but the refrigerant fluids typically used are very searching so that such heat exchangers are liable to leaks; the sealing material can, however, be chosen to suit the refrigerant fluids used and provide effective sealing for such fluids.

For many applications the ability to recycle the heat exchanger is very important, and in such applications it is a significant advantage that the heat exchanger can be made from only two different materials. Specifically, the header 30 can be manufactured entirely from aluminium, i.e. the extrusion 54 is of aluminium as are the end-plates 46 and 50. Also, the tubes 16 and fins 20 can be of aluminium also, so that the only non-aluminium component in the assembled heat exchanger is the sealing material.

In other applications it may be desirable to use more than one material in addition to the sealing material, notwithstanding the greater difficulty in recycling such heat exchangers. Specifically, in certain high-temperature applications it may be desirable to use different materials in different parts of the heat exchanger, and the “chamber” arrangement of the tube plates described herein can be utilised in an intermediate tube (or support) plate to support and join the respective ends of two adjacent tubes, the support plate supporting the junction between the tubes. Such a support plate can be used in a heat exchanger having headers 30 according to the invention, or in a heat exchanger having headers 12, 14 according to the prior art.

Accordingly, it can be arranged that the tubes to one side of the support plate are of a first material whilst the tubes to the other side of the support plate are of a different material. Also, if as is typical the tubes are fitted with fins or extended surface members, the material from which the fins are made, and the size and/or density of the fins, may differ to each side of the support plate. This can enable the heat exchanger designer to allow for the different temperature environments encountered by the tubes at different parts of the heat exchanger.

In particular, if the tubes to one side of the support plate are connected to the header having the inlet for the working fluid, they must be able to withstand the maximum temperature of the working fluid. In very high-temperature applications (e.g. those unrelated to motor vehicle radiators) this may require the tubes, and any fins which are carried thereby, to be of steel or titanium for example. However, since the working fluid will be cooled as it passes through the tubes, the temperature environment encountered by the tubes to the other side of the support plate will be lower, and the material of those tubes, and any fins carried thereby, can be of aluminium or other material which is suitable for heat exchanger applications but is not able to withstand very high temperatures.

In the heat exchangers of FIGS. 5 and 6 the sets of tubes 16a and 16b are interconnected at a tube plate 64 which acts as a support plate. The ends of the tubes 16a which are not shown in FIG. 5 are connected to a first header (such as header 14 or 30), and the ends of the tubes 16b which are not shown in FIG. 5 are connected to a second header (such as header 12 or 30); Accordingly, in a view such as that of FIG. 1 the support plate 64 would lie between the headers 12 and 14, and be substantially parallel thereto.

As with the headers 30, the support plate 64 has a number of openings 66 to receive the ends of the respective tubes 16a, 16b, and the support plate defines a chamber 70 which can be filled with a settable liquid sealant, the chamber having injection and fill openings 72 and 74.

The tubes 16a, 16b are a sliding interference fit within the openings 66, there being little or no gap therebetween through which liquid sealant could escape. In addition, though not shown in FIG. 5, the tubes 16a, 16b will typically carry fins (such as the fins 20 of FIG. 6) and it will desirably be arranged that the endmost fin engages the support plate in a similar way that the fin 20 engages the header 30 in FIG. 3; the presence of a fin engaging the support plate 64 will reduce or prevent the escape of any sealant through the openings 66.

Whether or not the ends of the tubes 16a, 16b abut inside the support plate, it is of course necessary to ensure that liquid sealant cannot enter the tubes, and a collar 76 is provided for this purpose. In this embodiment the collar 76 is internal of the tubes 16a, 16b, but it could instead be external, it being understood that an external collar must be located entirely within the support plate 64, or else the openings 66 be enlarged to accommodate the collar.

Though not shown in FIG. 5 or 6, the collar will typically carry an annular outwardly-projecting lip located substantially mid-way along the length of the collar, and against which the ends of the tubes 16a,b abut. The lip serves to ensure that a chosen length of the collar lies within each tube so as to reduce or avoid the possibility of sealant entering into the tubes.

In this embodiment the collar 76 is of PTFE and is an interference fit within the tubes 16a, 16b.

It is expected that one of the tubes (e.g. the tube 16a) will be assembled to the collar 76 prior to insertion into the support plate 64, the lip abutting the end of the tube. The tube and collar would then be inserted into the support plate and the other tube (16b) introduced thereinto to enage the collar 76.

The fins (if used) could be fitted to one or both of the tubes 16a, 16b after their insertion into the support plate, or pre-finned tubes could be used.

If desired or required, the support plate could be openable (or have a removable side wall) to allow access to the inside of the support plate whilst the tubes (which may be already finned) are assembled to the collars within the support plate, the support plate subsequently being closed (and sealed) prior to the injection of the liquid sealant.

The major benefit of utilising a support plate 64 between the headers 12 and 14 is that the material from which the tube 16a is made can differ from the material from which the tube 16b is made. Also, the materials from which the fins 20 are made can differ from tube 16a to tube 16b, as can the fin density and form, for example. This is particularly advantageous for heat exchangers for very high temperature applications, wherein the tubes 16a can be of expensive material suited to very high temperatures whilst the tubes 16b can be lower cost material not suited to such high temperature environments, it being determined that the working fluid flowing through the tubes 16a has cooled to a suitable temperature before it enters the tubes 16b.

Clearly, more than two temperature environments can be catered for within the heat exchanger, if desired, by utilising two (or more) support plates between the headers, the tube (and fin, as applicable) materials in each section being suited to the temperature environment encountered thereby. Also, a support plate can if desired be used to provide intermediate support in embodiments in which the tubes 16a, 16b are of the same material.

As above indicated, the tubes can be acircular, for example elliptical. It will be understood that it is not possible to drill elliptical openings in the tube plate walls, and to avoid the difficulty of stamping or punching out such openings in a double-walled structure it may be preferable or necessary to stamp or punch each tube plate wall separately. FIG. 7 shows a tube plate 80 configured as a support plate similar to that of FIGS. 5 and 6, though it will be understood that the arrangement could also be utilised in a tube plate similar to that of FIG. 2, FIG. 3, or FIG. 4.

In this embodiment the support plate 80 has a first tube plate wall 82 which is separable from the remainder of the support plate, and in particular from the second tube plate wall 84. The openings 86 can therefore be punched or stamped into the first tube plate wall 82 and the second tube plate wall 84 when these parts are separated. The first tube plate wall 82 is connected to the second tube plate wall 84 subsequent to the stamping or punching of the openings 86.

In this embodiment the connection is effected by relative sliding movement of the cooperating formations 90 (in the direction perpendicular to the plane of the paper as drawn), but in other embodiments can be effected by other suitable means, for example welding.

FIGS. 8 and 9 shown another embodiment of tube plate 180 in which the tube plate walls (comprising a first tube plate wall 132 and a second tube plate wall 134) are manufactured separately. In this embodiment the tube plate 180 is designed to be secured to a header 130, the header 130 and the tube plate walls being formed as extrusions of aluminium. Other methods of manufacture, and other materials (or material combinations if desired) could, however, be utilised.

The header 130 has a wall 92 to which the tube plate 180 is secured. In this embodiment the header 130 has a pair of flanges 94 which cooperate with formations of the first tube plate wall to secure the first tube plate wall 132 (and consequently the tube plate 130) thereto, but in other embodiments the tube plate can be welded, chemically bonded or otherwise secured to the header.

The second tube plate wall 134 and the first tube plate wall 132 also have cooperating formations 96 by which these components are secured together.

It will be understood that the respective cooperating parts allow the first tube plate wall 132 and the second tube plate wall 134 to be clipped together in the direction of arrow A in FIG. 8.

The openings for the tubes are not shown in FIGS. 8 and 9, though openings in the tube plate walls 132 and 134 such as those of the other embodiments shown would be provided, sized and shaped to match the tubes (also not shown). In addition, it will be understood that one or more openings must be provided in the wall 92 so that the header 130 can communicate with the tubes. It is not necessary that the openings in the wall 92 match the tubes since no sealing is required at that wall, and instead a single opening can be provided to accommodate all of the tubes. If the tube plate 180 is being secured to the header 130 by the flanges 94 only then a large proportion of the wall 92 could be removed, but if the tube plate is being secured by chemical bonding for example a smaller proportion would typically be removed to leave a larger surface for bonding. In another embodiment, however, the wall 92 is not present and the tube plate walls 132 and 134 are secured to the header by the interengagement of the cooperating parts 94 and 96 alone.

When the tube plate 80 in the embodiment of FIG. 7, or the tube plate 180 and header 130 in the embodiment of FIGS. 8 and 9, has been assembled, end-plates (such as 46, 50 for example) can be fitted to retain the respective components in position. Finally, the tubes can be inserted into the (aligned) openings (such as 86).

It will be understood, in embodiments in which the tube plate walls are manufactured separately, that subsequent welding is not required, because the sealant will infill any gaps between the relative parts providing the gaps therebetween are sufficiently small. It is expected to be relative easy to ensure that the tube plate walls (and the header is present) can be made with sufficiently small clearances to prevent leakage of sealant.