WO1993003318A1

WO1993003318A1 - Bayonet heat exchanger

Info

Publication number: WO1993003318A1
Application number: PCT/AU1992/000397
Authority: WO
Inventors: Ronald Albert Pain
Original assignee: Ronald Albert Pain
Priority date: 1991-07-31
Filing date: 1992-07-31
Publication date: 1993-02-18
Also published as: NZ243797A

Abstract

A media pathway (1) suitable for use in an opposed bayonet heat exchanger is formed in the annulus (2) between a pair of substantially concentric tubes (3, 4) by the provision of a pair of spaced baffles (5, 6) extending along the annulus so as to divide the annulus into two substantially arcuate chambers (2a, 2b). The spaced baffles are each formed as a flaring in the wall of one of th tubes which projects across the annulus.

Description

BAYONET HEAT EXCHANGER

BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION

The present invention relates to improvements in or relating to heat exchangers and has particular application in relation to indirect heat exchangers of the opposed bayonet type.

Indirect heat exchangers are devices to direct the flow of one fluid past another in order to exchange heat without mixing of the fluids. Heat exchangers are used in a wide variety of industrial processes and find wide application in the chemical, pharmaceutical and food industries. Heat exchangers may be utilised for the heating and/or the cooling of a product. Examples of applications for heat exchangers in the food industry include the pasteurisation and UHT treatment of food products, the cooling of juices, the heating of pie and pastry fillings and the cooling of fruit slurries.

Heat exchangers of varying types and efficiencies are well known including the plate heat exchanger, the shell and tube heat exchanger, and the concentric tube heat exchanger. These broad generic types of heat exchanger come in a multiplicity of forms and with various configurations to enhance heat transfer. For applications in the food and pharmaceutical industries, any contamination between the heating or cooling media and the product undergoing treatment is particularly serious. However, the sometimes wide fluctuations in temperature and the high pressures involved, particularly with viscous products, can produce severe stresses and make the sealing of heat exchanger components critical and rather difficult. Moreover, in order to provide efficient heat transfer properties it is preferable that the heating or cooling medium has a relatively large effective surface area and is distributed substantially evenly over the heat transfer surface so as to minimise hot spots or cold pockets. Bayonet heat exchangers have a particular advantage in dealing with thermal stresses because they require fixing at one end only, thereby allowing the heat exchanger to expand and contract freely. The problem in. all bayonet type heat exchangers is to produce an efficient flow path for the fluid within the bayonet that is economical to construct. 2. DISCUSSION OF THE PRIOR ART

A common prior art type of bayonet heat exchanger construction has an inner guide tube which conveys fluid to the far end of the outer tube from where the fluid contacts a heat transfer surface as it returns from the far end.

A problem with this construction is that the inner guide tube which conveys the fluid to the far end of the outer tube, plays no part in the heat transfer process and is therefore a wasted surface from this point of view. It also reduces the compactness of the heat exchanger, which may be an important parameter in some applications.

Heat exchangers of the opposed bayonet type are one variation of concentric tube heat exchanger which has been proposed. In opposed bayonet heat exchangers, a pair of separate media paths is formed in annular chambers between concentric tubes and the respective paths are interleaved between one another so as to form a product channel between the concentric tubes forming the media paths. Particular examples of such opposed bayonet heat exchangers have been previously proposed by Soderstrom in U.S. Patent 2,870,997 and by argittai in U.S. Patents 3,612,002 and 4,215,743.

Soderstrom proposed a heat exchanger consisting of concentric tubes thrust into each other and secured to the opposite ends of the housing, the inner ends of the tubes being free and the walls being located at a distance from each other so that flow passages or channels are formed in the space between them for the media. Soderstrom proposed the inclusion of guide blades in the flow passages to form a meandering passage for the product to flow therein. Soderstrom also proposed the use of guide tubes within the media pathway so as to direct the incoming media to the far end of the media pathway. However, such guide tubes play no part in the heat transfer process and hence introduce the disadvantages referred to above. Moreover, the Soderstrom proposal did not include a clearly delineated media pathway that could be economically constructed.

Margittai proposed in U.S. Patent 3,612,002 a series of concentric annular assemblies arranged for removable mounting within a shell. In the Margittai proposal the problem of media distribution was not addressed and consequently media flow would have been uneven over the heat transfer surface and performance extremely poor. In addition the entire construction was complex requiring numerous seals with a consequent propensity to failure and/or product contamination. In U.S. Patent 4,215,743 Margittai proposed improvements on this arrangement which included a double helix to lead the heating medium flowing down and up inside the hollow concentric cylinders and also processes for the manufacture of helical elements on the surface of the cylindrical elements.

The Margittai arrangement is described in U.S. Patent 4,215,743 as a cartridge heat exchanger made up of any number of double walled cartridges placed one inside the other like a double-ended collapsible telescope. The heating or cooling medium circulates inside the cartridges in a double helix path from the largest to the smallest cartridge or vice versa. The product flows in a helix or spiral between the cartridges. Baffles or dividers inside the cartridges direct the cooling medium. The Margittai arrangement suffers from a number of deficiencies. In particular, the baffles or dividers are composed of wire welded externally to a tube. Such a procedure is labour intensive and hence expensive. Moreover, such an arrangement precludes a particularly close fit between the wire and the opposing wall without expensive machinery. Alternatively, the entire construction, i.e. wire, inner and outer tubes must be fully welded together in a leakproof manner as Margittai proposed. This would be an expensive labour intensive process. In addition the use of a plurality of concentric cartridges in the Margittai arrangement results in difficulties in sealing and assembly. SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide, in one embodiment, a media pathway incorporating baffles suitable for use in bayonet heat exchangers.

It is a further object of the present invention to provide, in one alternative embodiment, a heat exchanger incorporating baffles according to the present invention.

It is a still further object of the present invention to provide in yet another embodiment, an opposed bayonet heat exchanger incorporating baffles according to the present invention.

The present invention accordingly provides, in one embodiment, a media pathway suitable for use in an opposed bayonet heat exchanger; said media pathway being formed in the annulus between a pair of substantially concentric tubes by the provision of at least a pair of spaced baffles extending along the annulus whereby to divide the annulus into at least two substantially arcuate chambers along at least a majority of the length of the annulus, the spaced baffles each being in the form of a deformation in the wall of at least one of the tubes, said deformation projecting substantially across the annulus.

The present invention also provides, in another embodiment a heat exchanger incorporating at least one media pathway formed in the annulus between a pair of substantially concentric tubes by the provision of at least a pair of spaced baffles extending along the annulus whereby to divide the annulus into at least two substantially arcuate chambers along at least a majority of the length of the annulus wherein the spaced baffles are each in the form of a deformation in the wall of at least one of said tubes, said deformation projecting substantially across the annulus, and wherein an inlet and an outlet are provided for the inflow and outflow of media into and out from said annulus.

The present invention still further provides, in a particularly preferred embodiment, an opposed bayonet heat exchanger comprising; a pair of separate media pathways interleaved with one another whereby to form a product channel therebetween wherein each of said media pathways is formed by at least one pair of substantially concentric tubes, sealingly connected to one another whereby to form an annulus therebetween; and wherein at least a pair of spaced baffles extends along said annulus whereby to divide said annulus into at least two substantially arcuate chambers along at least a majority of the length of said annulus to form a return pathway extending longitudinally of said annulus, wherein said spaced baffles are each in the form of a deformation in the wall of at least one of said tubes, said deformation projecting substantially across the annulus, and wherein an inlet and an outlet are provided for the inflow and outflow of media into and out from said annulus.

The deformations may extend inwardly and/or outwardly from a tube wall. The deformations may be in the form of longitudinal grooves extending substantially along either or both tubes. The longitudinal grooves may be substantially straight. Substantially helical longitudinal grooves are also envisaged within the scope of the invention.

It is particularly preferred that the deformations forming baffles according to the present invention are formed in the outermost tube of a substantially concentric pair. The deformations preferably project inwardly from the outer tube of a pair toward the inner tube of the pair. Most preferably the deformations abut the inner surface of the opposing tube. The arrangement is preferably such that the baffles form a tight friction fit with the opposing tube whereby to minimise leakage of media across the baffle.

Substantially straight longitudinal baffles are particularly preferred where the media may include steam. Preferably a pair of longitudinal baffles extends along a pair of substantially concentric tubes. The baffles are preferably substantially evenly circumferentially spaced within an annulus whereby to form two substantially arcuate chambers of substantially equal size.

To facilitate the positioning of the inner tube relative to the outer tube a plurality of positioning deformations may be provided in the form of short grooves in the inner and/or outer tube of a pair. Such grooves may take the same form as baffles but extend only for a short distance along a pathway. A plurality of such positioning deformations may be spaced longitudinally whereby to position the inner tube along its length relative to the outer tube of a pair. The baffles according to the present invention need not be affixed to the adjacent tube but may be held in abutting relationship by friction with the internal wall of the adjacent tube. In such an arrangement considerable pressure may be required to longitudinally assemble the concentric tubes. Deformations provided to act as baffles in accordance with the invention are capable of withstanding such assembly pressures without any significant damage.

The baffles may be arranged in a variety of configurations. The arrangement of the baffles may be irregular to assist for, example, in the creation of turbulence within the media path. A helical configuration of baffles is preferred, -particularly where operations involve conveying fluid at high pressures, because such an arrangement provides mechanical radial support to the tube structures.

A pair of adjacent tubes may include one or more pairs of baffles thereby providing one or more media flow paths within a single annulus.

In the vicinity of the seal between adjacent concentric tubes remote from the inlet, there is preferably a header zone free of any baffles. In this arrangement fluid passed in one direction along the path formed between two baffles and a pair of tubes is free to cross over in the header zone to another similarly formed path flowing in the return direction thereby forming a return pathway.

Adjacent the inlet and outlet end of a path formed in accordance with the present invention at least one pair of baffles preferably extends to the near end of the annulus so as to resist direct cross over of media from inlet to outlet. In this way incoming media is directed by the baffles to the far end of the annulus remote from the inlet, where the media may cross over to the return pathway in a header zone and return to the outlet.

As will be appreciated, the inlet and outlet are preferably both located adjacent the same end of a pair of concentric tubes forming a media path according to the present invention.

An opposed bayonet heat exchanger according to the present invention is preferably formed in at least two separable sections. The sections are preferably adapted to be separated to facilitate cleaning, removal of blockages, inspection and other maintenance. Each of the separate media paths may be incorporated into a different one of the separable sections.

In a most preferred arrangement according to the invention, a heat exchanger is formed in two separable sections. Each of the separable sections preferably includes a different one of the pair of separate media paths.

As the product channel is formed by the external surfaces of the tubes forming the media paths, separation of a heat exchanger according to the invention may effectively involve dismantling of the product channel thereby facilitating cleaning and other maintenance.

Each of the separable sections of a heat exchanger according to the invention may include securement means for securing the separable sections. Any form of securement means capable of retaining the separable sections in assembled relationship at the temperatures and pressures of intended operations may be utilised in accordance with the present invention.

Preferably the securement means comprises clamp means for clamping the separable sections, together. The clamp means may include one or more outwardly extending flanges on each of the separable sections. The flanges may be constructed and arranged to facilitate securing the separable sections. The flanges are preferably apertured.

In assembled relationship, the apertures are preferably aligned whereby a bolt or similar means may pass through the flanges of separate sections whereby to urge the sections toward one another thereby securing the sections. Other forms of securement means for urging the flanges toward one another are also envisaged within the scope of the present invention.

The securement means may be located adjacent one end of a heat exchanger according to the present invention.

Most preferably, the securement means comprises an outwardly extending flange extending around each of the separable sections and adapted to receive a plurality of bolts for urging the sections toward one another.

To complete the seal between separable sections, a gasket preferably in the form of an o-ring is provided. The gasket may be positioned so as to be sandwiched between the mating surfaces of the separable sections.

The gasket may be positioned so that, should gasket failure occur, no intermixing between product and media occurs. Preferably, gasket failure will result only in leakage of media to atmosphere which is readily observable. Although reference is made herein to media pathways and a product channel, it is to be appreciated that in some cases it may be preferable for the product being heated or cooled to be passed through the media pathways and for the heating or cooling media to be passed through the product channel. The final selection as to which component is to pass through which pathway or channel may be dependent upon such considerations as viscosity, pressure, temperature change desired, volume and other physical and chemical parameters.

BRIEF DESCRIPTION OF THE DRAWINGS

To further assist in the understanding of the present invention, particularly preferred embodiments of the invention will now be described in relation to the drawings.

In the drawings:

Figure 1 is a cut-away perspective view of a media pathway suitable for use in an opposed bayonet heat exchanger in accordance with one embodiment of the present invention;

Figure 2 is a longitudinal cross-sectional view of the media pathway of Figure 1 taken along the line 2-2 of Figure 1; Figure 3 is a transverse cross-sectional view of the media pathway of Figure 1 taken along the line 3-3 of Figure 2;

Figure 4 is a cross-sectional view of a single bayonet heat exchanger in accordance with one embodiment of the present invention;

Figure 5 is a longitudinal cross-sectional view of an opposed bayonet heat exchanger according to one embodiment of the present invention;

Figure 6 is a transverse cross-sectional view of the heat exchanger of Figure 5 taken along the line 6-6 of Figure 5;

Figure 7 is a cross-sectional view of an embodiment of an opposed bayonet heat exchanger according to another embodiment of the invention; Figure 8 is a transverse cross-sectional view of the heat exchanger of Figure 7 taken along the line 8-8 of Figure 7;

Figure 9 is a cross-sectional view of an embodiment of an opposed bayonet heat exchanger according to yet another embodiment of the invention;

Figure 10 is a transverse cross-sectional view of the heat exchanger of Figure 9 taken along the line 10-10 of Figure 9;

Figure 11 is an exploded cross-sectional view of the heat exchanger of Figure 9 showing the separation of the two bayonets thereof; Figure 12 is a perspective view of an alternative pathway according to the present invention showing helical baffles;

Figure 13 is a longitudinal cross-sectional view of an opposed bayonet heat exchanger according to a still further embodiment of the invention; and

Figure 14 is an exploded perspective view of the heat exchanger of Figure 13. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As shown in the accompanying drawings in which like features are designated by like numerals in different

Figures, media pathway 1 (shown in Figure 1) is formed in the annulus 2 between a pair of substantially concentric tubes 3 and 4.

Media pathway 1 includes a pair of spaced baffles 5 and 6. Spaced baffles 5 and 6 extend along annulus 2 whereby to divide annulus 2 into two substantially arcuate chambers 2a and 2b as is clearly seen in Figure 3.

At either end, concentric tubes 3 and 4 are sealed. The sealing can be performed by an outward flaring of inner tube 4 at either end and a corresponding inward flaring of outer tube 3 whereby the annulus is substantially bridged and the respective ends welded together so that annulus 2 is a substantially enclosed chamber. Access to annulus 2 for media to flow within the pathway is provided via inlet 7 and outlet 8. It will be appreciated however that in the arrangement shown in Figure 1 the direction of media flow can be reversed so that 8 may operate as the inlet and 7 as the outlet.

As clearly seen in Figure 3, baffles 5 and 6 are formed by the inward deformation of the wall of outer tube 3. The deformations shown in Figures 1 and 3 are in the form of longitudinal grooves extending substantially along outer tube 3. The longitudinal grooves are substantially straight in the embodiment shown in Figure 1, however as shown in corresponding Figure 12 grooves 5,6 which extend substantially helically along either or both of tubes 3 and 4 are also envisaged within the scope of the present invention.

As clearly seen in Figure 3 the baffles 5,6 form a tight friction fit with opposing inner tube 4 so as to minimise leakage of media across baffles 5 and 6 between arcuate chambers 2a and 2b.

In the vicinity of the seal between tubes 3 and 4 which is remote from the inlet and outlet end there is a header zone 9 which is free of any baffles. In the arrangement shown in Figure 1 media passed in inlet 7 cannot progress directly to inlet 8 in view of baffles 5 and 6. Incoming media is therefore forced toward header zone 9 as indicated by the arrows in Figure 1. At header zone 9 media is free to pass over the top of baffles 5 and 6 and into the return pathway 2b. Media flows along return pathway 2b and is free to exit via outlet 8.

Figure 4 shows a single bayonet heat exchanger 10 which includes a media pathway 1 of the general type depicted in Figure 1. in this arrangement pathway 1 which may be considered as single bayonet 1 is located within jacket 11. The product being heated (or cooled) enters jacket 11 via fluid inlet 12. The fluid circulates as indicated by the arrows and in view of the thermosiphon effect fluid entering inlet 12 will tend to rise within inner tube 4 of bayonet 1. On reaching the outlet end of jacket 11 the fluid may either exit via outlet 13 or via the thermosiphon effect be recycled to the inlet end and again flow through the inner tube 4.

The heating (or cooling) media enters inlet 7 passes to the remote end of bayonet 1 where it crosses over from annulus 2a to annulus 2b to return and exit via outlet 8 in the manner already described in detail in relation to Figure 1. Figures 5, 7 and 9 each show variations of opposed bayonet type heat exchangers produced in accordance with the present invention. The embodiment shown, in Figure 5, comprises a pair of single pathway bayonets 14,15 telescopically arranged to form product channel 25.

The embodiment shown, in Figure 7, comprises a twin pathway bayonet 14 telescopically arranged relative to single pathway bayonet 15 to form product channel 25.

The embodiment shown in Figure 9 comprises a pair of twin pathway bayonets 14 and 15 telescopically arranged to form product channel 25.

The invention will be further described with particular reference to the preferred embodiment shown in Figures 9, 10 and 11 however like features in the other embodiments indicated by like numerals are understood to operate in like manner to that described with particular reference to Figures 9, 10 and 11.

In the embodiment shown in Figures 9, 10 and 11 bayonet 14 comprises a pair of media pathways 14a and 14b. Bayonet 15 comprises a pair of media pathways 15a and 15b. When bayonets 14 and 15 as shown in Figure 11 are assembled by being telescoped into one another, as shown in Figure 9, the separate media pathways 14a and 14b are interleaved with separate media pathways 15a and 15b to form product channel 25.

The respective ends of the concentric tubes of each pair which form pathways 14a, 14b, 15a, 15b, etc. are sealed adjacent the end remote from the inlet and outlet for that pathway. In the case of the opposed bayonet heat exchanger of the type shown in Figure 11, each of bayonets 14 and 15 have separate media inlets 16 and 17 respectively and separate media outlets 18 and 19 respectively. A single product inlet 20 and a single product outlet 21 allow for the entry and exit of a product to and from product channel 25.

The separable sections 14 and 15 of a double bayonet heat exchanger according to the invention include securement means 28 which in the embodiments shown in the drawings comprises a pair of outwardly extending flanges 22 and 23 one on each of the separable sections. Flanges 22,23 may be apertured or otherwise adapted for being urged toward one another. In the embodiments shown in Figures 4, 5, 7 and 9, securement means 28 comprises radially spaced nut and bolt arrangements 29 which may be tightened to urge flanges 22,23 toward one another to secure the bayonets 14,15 in assembled relationship. An o-ring or other seal 24 is captured between flanges 22,23 whereby to seal the heat exchanger upon assembly. As clearly seen from the drawings, the seal 24 is positioned such that should seal failure occur no intermixing between product and media would occur but rather the result would be a leakage of media to atmosphere which would be readily observable.

As best seen in Figure 11 a manifold arrangement is provided adjacent the inlet end of each bayonet. In the case of bayonet 14 the manifold allows fluid entering inlet 16 to proceed along either arm of pathway 14b. However, a baffle is required within the manifold to prevent fluid entering inlet 16 and exiting directly from outlet 18. Such baffles 26 and 27 are shown in Figure 11.

This problem is perhaps best observed in bayonet 15 in Figure 11 where baffle 27 is inserted within the manifold of bayonet 15 whereby to prevent direct passage of media from inlet 17 to outlet 19. Baffle 27 extends into the annuli forming pathways 15a and 15b as indicated in dotted outline. The baffle 27 within the pathways 15a, 15b comprises a depression as previously described which sealingly engages a wall within the manifold. Incoming media from inlet 17 is accordingly forced along either arm of pathway 15b to the end remote from inlet 17 at which point the fluid is beyond the free end of baffle 27 and therefore may cross over in the header zone 9 of the bayonet .15 to corresponding return pathways 15a and 15b for the return to exit bayonet 15 via media outlet 19.

The flow within pathways 14a, 14b is similarly directed by baffle 26.

As best seen in Figure 9, product entering the heat exchanger via product inlet 20 passes initially along a central core 30 and over the external. surfaces of the tubes forming pathways 14b, 15b, 14a and 15a as it passes along product channel 25 to product outlet 21.

Core 30 is relatively large in cross sectional area when compared with the remainder of product channel 25 and hence would be relatively less efficient. The alternative arrangement shown in Figures 13 and 14 illustrates the use of insert 31 to further utilise the area of core 30.

The alternative arrangement shown in Figures 13 and 14 comprises a pair of single pathway bayonets 14,15 telescopically arranged to form product channel 25. The arrangement is somewhat similar to that of Figure 5 however baffles 26,27 are arranged to extend substantially helically along the concentric tubes in the embodiment of Figures 13 and 14.

Securing means 28 in the embodiment of Figures 13 and 14 comprises a threaded flange 32 on bayonet 15 adapted to threadedly receive nut 33. Nut 33 is captured on bayonet 14 by flange 34 so that as nut 33 is screw tightened onto threaded flange 32 the flanges are urged toward one another thereby securing bayonets 14,15 in assembled relationship. In this alternative arrangement bayonet 14 is shown as including a threaded flange 35 on product inlet 20 whereby to facilitate connection of'product inlet 20 to the source of product during use.

In place of a sealed end remote from the inlet/outlet end as shown in Figure 5 the alternative arrangement shown in Figures 13 and 14 includes removable cap 36 which is mounted on the otherwise open end of bayonet 15 via nut 37 which threadingly engages threaded flange 38. As nut 37 is tightened onto flange 38 cap 36 is urged against o-ring 39 whereby to seal the end of bayonet 15.

Cap 36 may act as an inspection port allowing access to product channel.25 and in particular core 30 thereof without the need to fully dismantle the heat exchanger.

In the particularly preferred embodiment shown in Figures 13 and 14 insert 31 is mounted in cap 36 for insertion within core 30. Insert 31 comprises a single tube twisted back on itself to provide a return pathway for fluid from inlet 40 to outlet 41 (or vice versa). This arrangement provides a facility for passing the same or a different heating/cooling medium or product to be circulated through the core to provide additional heat exchanging surfaces.

If no fluid is passing through insert 31 during use the insert may still serve the valuable function of adding turbulence to product passing through core 30. As will be appreciated by those skilled in the art alternative forms of insert including twisted metal flats and other arrangements to facilitate stirring but not necessarily allow for additional fluid circulation are also envisaged within the scope of the present invention.

The present invention, as described herein, provides a number of advantages over the known prior art. For example, the use of baffles to direct the passage of media as described herein allows all surfaces of the tubes with the exception of the outermost surface to be used for heat exchange purposes. Such an arrangement provides a particularly efficient heat exchanger.

Another advantage provided by the present invention is that the series arrangement of the product channel obviates the problems associated with parallel product flow paths. Uneven flow may be of particular concern where the product is temperature or sheer sensitive, particularly with products comprising particulate or fibrous matter.

A further advantage provided by the present invention is that a single gasket is used such as o-ring 24 thereby minimising the problems associated with gasket breach and leakage. Furthermore, the breach of the o-ring gasket 24 will only result in product bleeding to the atmosphere. This is readily observable by an operator and thereby eliminates the serious problem of media/product mixing occurring due to gasket failure. As those skilled in the art will realise, product/media intermixing may have dire consequences such as contamination of the product, particularly in the food and pharmaceutical industries.

Yet another advantage provided by the present invention is that as a result of the interleaved arrangement of the coaxial tubes, the arrangement may be simply disassembled by disengagement of the securement means 28 and separation of bayonet 14,15 as shown in Figure 11 to enable access for repairs, maintenance and/or clearance of blockages.

Because the media pathways are subject on both sides to the pressure of the product these elements can be considered to be subject to equal pressures on both sides. Consequently this design is particularly advantageous for applications in which high product pressures are encountered such as tomato paste pasteurisation.

Finally, in embodiments made in accordance with the present invention, it is possible to locate all product and media inlets and outlets at the one end thereby reducing the cost and complexity of the associated plumbing required (not shown in the drawings) for installation of a heat exchanger according to the present invention.

It will be appreciated by those skilled in the art that the embodiments described herein are referred to only by way of example to describe the inventive concept per se. However, the scope of the invention is not intended to be limited by reference to terms such as "concentric" and "annular" in the description of the tubes. It is to be appreciated that it is well within the scope of the invention that the cross-section of such tubes could be substantially rectangular, ovaloid or elliptical without departing from the essence of the invention. Furthermore, references to the heat exchanger being of a linear or longitudinal configuration are not intended to exclude such possibilities as L-shaped, S-shaped or curved exchanger configurations. It will further be appreciated by those skilled in the art that various components of the present invention may be made from a range of materials possessing as wide a range of physical and chemical properties as the products which can be treated by heat exchange methods. As an indication of the types of materials that may be used, particularly in the manufacture of the tubes such materials as steel, stainless steel, copper, bronze, nickel alloys, titanium, plastic and even glass may be used. Clearly, where pressures of 150 to 200 bar are involved, particularly in the processing or products such as heavy viscous pastes, cheese and some pharmaceuticals, materials possessing very strong pressure- resistant properties may be required. Furthermore, although it is within the scope of this invention to use cast or moulded components, it is preferred that component parts be joined predominantly by welding means, particularly when high temperatures and pressures are experienced.

While it has been convenient to describe the invention herein in relation to particularly preferred embodiments, it is to be appreciated that other constructions and arrangements are also considered as falling within the scope of the invention. Various modifications, alterations, variations and/or additions to the constructions and arrangements described herein are also considered as falling within the scope and ambit of the present invention.

Claims

CLAIMS :

1. A media pathway suitable for use in an opposed bayonet heat exchanger; said media pathway being formed in the annulus between a pair of substantially concentric tubes by the provision of at least a pair of spaced baffles extending along the annulus whereby to divide the annulus into at least two substantially arcuate chambers along at least a majority of the length of the annulus, the spaced baffles each being in the form of a deformation in the wall of at least one of said tubes, said deformation projecting substantially across the annulus.

2. A media pathway according to claim 1 wherein said deformations comprise longitudinal grooves extending substantially along either or both of said tubes.

3. A media pathway according to claim 2 wherein said grooves extend substantially helically along either or both of said tubes.

4. A media pathway according to claim 2 wherein said deformations project inwardly from the outer tube of said pair toward the inner tube of said pair.

5. A media pathway according to claim 4 wherein said baffles form a tight friction fit between the tubes of said pair whereby to minimise leakage of media across said baffles.

6. A media pathway according to claim 5 wherein said baffles are circumferentially spaced substantially evenly within said annulus whereby to form two substantially arcuate chambers of substantially equal size.

7. A media pathway according to claim 6 which further includes a plurality of grooves in the wall of either or both of said pair of substantially concentric tubes, said grooves each extending for a short distance along said pathway whereby to position the inner tube along its length relative to the outer tube of said pair.

8. A heat exchanger incorporating at least one media pathway formed in the annulus between a pair of substantially concentric tubes by the provision of at least a pair of spaced baffles extending along the annulus whereby to divide the annulus into at least two substantially arcuate chambers along at least a majority of the length of the annulus wherein the spaced baffles are each in the form of a deformation in the wall of at least one of said tubes, said deformation projecting substantially across the annulus, and wherein an inlet and an outlet are provided for the inflow and outflow of media into and out from said annulus.

9. A heat exchanger according to claim 8 wherein said inlet and said outlet are both positioned adjacent the same end of said pair of concentric tubes and wherein a header zone is provided adjacent the opposite end of said pair of concentric tubes wherein said header zone is free of baffles whereby fluid passed from said inlet in one direction along said pathway is free to cross over in the header zone to another similarly formed pathway and flow in the return direction to said outlet.

10. A heat exchanger according to claim 9 wherein adjacent said inlet and outlet at least one pair of said baffles extend to the near end of said annulus whereby to resist direct cross over of media from said inlet to said outlet.

11. A heat exchanger according to claim 10 wherein said deformations comprise longitudinal grooves extending substantially along either or both of said tubes.

12. A heat exchanger according to claim 11 wherein said grooves extend substantially helically along either or both of said tubes.

13. A heat exchanger according to claim 11 wherein said deformations project inwardly from the outer tube of said pair toward the inner tube of said pair.

14. A heat exchanger according to claim 13 wherein said baffles form a tight friction fit between the tubes of said pair whereby to minimise leakage of media across said baffles.

15. A heat exchanger according to claim 14 wherein said baffles are circumferentially spaced substantially evenly within said annulus whereby to form two substantially arcuate chambers of substantially equal size.

16. A heat exchanger according to claim 15 which further includes a plurality of grooves in the wall of either or both of said pair of substantially concentric tubes, said grooves each extending for a short distance along said pathway whereby to position the inner tube along its length relative to the outer tube of said pair.

17. An opposed bayonet heat exchanger comprising; a pair of separate media pathways interleaved with one another whereby to form a product channel therebetween wherein each of said media pathways is formed by at least one pair of substantially concentric tubes, sealingly connected to one another whereby to form an annulus therebetween; and wherein at least a pair of spaced baffles extends along said annulus whereby to divide said annulus into at least two substantially arcuate chambers along at least a majority of the length of said annulus to form a return pathway extending longitudinally of said annulus, wherein said spaced baffles are each in the form of a deformation in the wall of at least one of said tubes said deformation projecting substantially across said annulus, and wherein an inlet and an outlet are provided for the inflow and outflow of media into and out from said annulus adjacent the same end of said tubes and wherein a header zone is provided adjacent the opposite end of said tubes whereby fluid passed from said inlet in one direction along said pathway is free to cross over in the header zone to another similarly formed pathway and flow in the return direction to said outlet.

18. An opposed bayonet heat exchanger according to claim 17 wherein said deformations each comprise a longitudinal groove extending substantially along either or both of said tubes.

19. An opposed bayonet heat exchanger according to claim 18 wherein said heat exchanger is formed in two separable sections and further includes securement means capable of retaining the separable sections in assembled relationship at the temperatures and pressures of the intended operation of said heat exchanger.

20. An opposed bayonet heat exchanger according to claim 19 wherein said securement means includes an outwardly extending flange on each of said separable sections and clamping means adapted to urge said flanges against one another, wherein an o-ring gasket is sandwiched between the mating surfaces of said flanges when said separable sections are in assembled relationship.

21. An opposed bayonet heat exchanger according to claim 20 wherein said grooves extend substantially helically along either or both of said tubes.

22. An opposed bayonet heat exchanger according to claim 21 wherein said deformations project inwardly from the outer tube of each of said pair toward the inner tube of each of said pair.

23. An opposed bayonet heat exchanger according to claim 22 wherein each of said baffles forms a tight friction fit between the tubes of each of said pair whereby to minimise leakage of media across each of said baffles.

24. An opposed bayonet heat exchanger according to claim 23 with further includes a plurality of grooves in the wall of at least one tube in each of said pairs of substantially concentric tubes, each of said plurality of grooves extending for a short distance along said pathway whereby to position the inner tube along its length relative to the outer tube of each of said pair.