Removable Heat Exchanger Inserts

Abstract

A heat exchanger or chemical reactor comprising a heat exchange body defining a plurality of flow passages and a removable insert defining secondary heat exchanger surfaces retained within at least one of the flow passages by insert retention means. The insert comprises one or more plate(s) having perforations to define discreet fluid flow channels extending across the plate(s) and wherein said one or more of the plates is provided with a carrier for a catalyst or adsorbent.

Description

This invention relates to heat exchangers. It is particularly, but not exclusively, concerned with heat exchangers that are to be used as chemical reactors and, although not intended to be limited thereto, it will be more specifically described below with particular reference to catalytic reactors.

Heat exchanger constructions are well known in which passageways for fluid are provided between adjacent walls defined by parallel spaced plates which provide primary heat exchange surfaces, and in which the passageways contain secondary heat exchange surfaces in the form of fins, which may conveniently be in the form of a corrugated sheet or finning extending along the passageways.

It is conventional practice to braze or otherwise bond the corrugated finning to the passageway walls during brazing or otherwise bonding of the passageway walls to form the heat exchanger structure. In other words, the corrugated finning is bonded in situ during the manufacture of the heat exchanger body and it is conventional practice to utilise the presence of the corrugated finning to assist in transmitting the loads applied by jigging during the bonding/brazing process.

Where the heat exchanger is to be used as a chemical reactor, it is frequently required that passageways contain catalyst to catalyse the desired reaction in the fluids passing through those passageways. For an exothermic reaction, the reactor may be designed to have passageways to carry a cooling fluid across the opposite faces of the primary surfaces to the faces contacting the reacting fluid so that the heat of reaction can be carried away. If the reaction is endothermic, a heating fluid may be needed to transfer heat across those primary surfaces to initiate the desired reaction.

Two basic systems have hitherto been proposed to introduce catalyst into those passageways carrying the fluid to be reacted. In one, the internal surfaces of the passageways are coated with a catalyst, usually in finely divided form, e.g. of particle size 150 microns or less. In the second, the passageways are packed with catalyst, which may, for example, be of particle size 2 to 3 mm or greater. The second system is more suitable for use with relatively open, unobstructed passageways whereas the first system is more suitable for use with smaller passageways which may contain secondary finning. It is usual to coat the catalyst onto the primary and secondary surfaces after they have been bonded together to avoid damage to the catalyst and its adhesion properties during the bonding process. The catalyst is applied by well known coating techniques in which a solution or suspension of the catalyst is brought into contact with the passageway surfaces by dipping, and/or flowing with the solution or suspension and then stoving at the appropriate temperature.

Packed catalyst particles of the second system can be removed when spent or contaminated simply by being forced out of the passageways, e.g. by means of a rod, and the passageways can then be repacked with fresh catalyst. Spent or contaminated catalyst of the first system is much more difficult to remove from the relatively complex internal passageway surfaces and the reactor, therefore, may have only a short service life and have to be scrapped when the catalyst is spent.

The Chemical Industry has traditionally utilised catalysts in order to initiate/control various chemical reactions but the applications are now becoming much wider. A significant growth in usage could occur with the advent of miniaturised chemical reactors in conjunction with the introduction of Process Intensification and Fuel Cells.

The traditional method of installing catalyst is to pack tubes/passageways with appropriate particles and control the temperature of the reaction by passing a cooling or heating medium over the outside of the tubes. Development of catalyst and processes has now resulted in a preference, for some applications, for finely divided catalyst particles to be coated onto the internal surfaces of the reactors. One method of enhancing the surface area available for coating and hence improving the performance of a reactor is to fit an insert into each passageway. The inserts are specially designed to meet these requirements.

Effective coating of the inserts can be more readily achieved and controlled with such a system.

Although more efficient than traditional methods, the coated catalyst may still have a reduced life as a consequence of fouling etc, requiring it to be capable of being changed more frequently. Thus having the opportunity of removing the insert, re-coating and re-installing would be particularly advantageous.

In a heat exchanger with relatively open passageways it may be desirable to provide an insert to increase the heat exchange capacity of the reactor. The ability to remove, clean and replace such inserts would also be desirable.

It is, therefore, an object of the invention to provide an improved heat exchanger, particularly useful as a catalytic chemical reactor, in which the above-mentioned problem of coated catalytic reactors can be obviated, and/or a heat exchanger in which inserts to increase heat exchange capacity can be removed, cleaned and replaced.

A further feature of the invention concerns solid catalysts, which are used in the chemical processing industry for the enhancement of chemical reactions Typically the catalyst would form a thin surface over which the process fluid flows Solids are widely used for other processing applications including adsorption processes both involving chemical reactions and as a physical process.

Adsorption is the action of molecules transferring from a fluid phase adsorbate (either gas or liquid) onto a solid phase adsorbent. This can result in a chemical reaction between fluid and solid, be a means for the solid to capture specific components from the fluid phase, in this way acting as a separator, or the structure acts as a storage device holding a fluid in place. Adsorbents are typically porous to provide a high surface area per unit volume. Typical adsorbents are silica gel and activated carbon.

Applications of adsorption include

• • heat pump adsorption cycles, where the adsorbent provides the means for holding the liquefied refrigerant during phase changes between gas and liquid, thereby releasing or absorbing heat (known as sorption chillers)
  • gas purification where one or more specific components in the gas can be removed from the bulk gas flow
  • to provide contact for chemical reactions between fluids and solids.

Adsorption is accompanied by the liberation of heat, even when there is no chemical reaction involved. Under many circumstances adsorption can be reversed so the captured component is desorbed by reversing the conditions (temperature, pressure) that were applied to promote adsorption. If the heat of adsorption cannot be removed by cooling, the capacity of the adsorbent will be reduced as its temperature increases.

Standard adsorbers consist of packed beds of granular or pellet adsorbent through which the process fluid passes.

It is a further object of the invention to provide an insert for receiving solid or granular adsorbent which can also act as a catalyst.

It is also known that processes can occur where it is desirable to separate one component from a process stream. This can occur, for example, during gaseous reactions when the removal of a reaction product can affect the equilibrium and therefore promote the production of more of that product. Membranes can also be used for this purpose.

Membranes can be in the form of ceramic, fibrous or polymeric solids. The membrane will allow the separation of a specific component or components, acting in the manner of a filter. Hydrogen is an example of a component that can be separated from gaseous streams through the use of a membrane.

A stack can be made up using inserts described herein, both slotted plate and pin-fin types.

According to one aspect of the invention there comprises a heat exchanger or chemical reactor comprising a heat exchange body defining a plurality of flow passages and a removable insert defining secondary heat exchanger surfaces retained within at least one of the flow passages, by insert retention means, characterised in that the insert comprises one or more plate(s) having perforations to define discrete fluid flow channels extending across the plate(s) and wherein one or more of the plates is provided with a carrier for a catalyst or adsorbent.

Optionally, the body comprises an elongate tube with the wall of the bore of the tube constituting a flow passage.

Preferably, one or more of the plates are of different thicknesses with respect to the other plates in such a stack. More preferably, the insert retention means is provided at least in part by the stack which is slightly greater in height than the height of the fluid passage to provide an interference or push fit.

Alternatively, insert retention means may be provided at least in part by resilient biasing means to urge the insert against the flow passage.

According to an optional feature of the invention, the insert retention means is provided at least in part by gripping means incorporated in the structure of said insert. The gripping means may be provided by a barbed external surface of the insert, the barbs being angled in a common direction.

In one class of embodiments, the insert is provided with a handle means for a user to insert or retract the insert from the heat exchange body. The handle means may also comprise a recess adapted to receive a pulling device. Preferably, the handle means further comprises a stepped transition in thickness.

In preferred embodiments where the insert comprises a plurality of stacked plates, each plate may include one or more apertures which are aligned in stacked condition.

Preferably, the longitudinal edges of the insert comprise protrusions dimensioned to provide an interference or push fit.

According to a further optional feature of the invention, in the plurality of stacked plates each plate has one or more slots that define the plurality of flow passages when the plates are stacked. Preferably, the catalyst when used is retained within the one or more slots.

More preferably the one or more slots are aligned to form a channel in the stack to receive a catalyst and/or an adsorbent.

In some embodiments, the adsorbent and/or the catalyst is a solid. The stack may further comprise one or more support plates having a plurality of support elements to support the solid within the channel. The support elements may be provided by ligaments interconnecting one or more pins formed in the plate, the pins providing a raised platform for the solid.

Alternatively, the catalyst and/or adsorbent may be granular and retained within the slots which are sized to prevent the granules from passing through the slots.

In other embodiments, the catalyst is coated on to the plates.

Optionally, the insert may further comprise a membrane for separating a component of the fluid flow.

A second aspect of the invention provides a shim for forming an insert useful in a heat exchanger or chemical reactor, the shim having a plurality of channels formed therein, and one or more cross members positioned across said channels. Preferably, the cross-members are of reduced thickness with respect to the plate.

There may further comprise an extension element hingedly connected to the plate and adapted to be folded out of alignment of the body to form handle means. The extension element may comprise a recess adapted to receive a pulling device. The extension element may also comprise a stepped transition in thickness.

In some embodiments, the shim may comprise a leading edge, which edge is tapered to aid insertion of the shim into the heat exchange body.

According to an optional feature of the second aspect of the invention, the shim comprises protrusions along the longitudinal edges of the shim. Optionally, the protrusions may be angled in a common direction.

The shim may also comprise one or more apertures.

The extension element may comprise a protruding portion that can be adapted to fold out of alignment of the body.

A third aspect of the invention comprises a heat exchanger or chemical reactor comprising a heat exchange body defining a plurality of flow passages and a removable insert defining secondary heat exchanger surfaces in interference fit with at least one of the flow passages, characterised in that the insert comprises a metal sheet folded to form corrugations extending along an axis and resilient biasing means to encourage the insert against said fluid flow passage.

According to an optional feature of the third aspect of the invention, the resilient biasing means may comprise one of the following, a leaf spring, a coil, or a stacked leaf spring.

Shims may be separated by a membrane, for example a membrane arranged to allow passage of one or more selected or desired species.

Exemplary embodiments will now be described by way of non-limiting example only with reference to and as illustrated in the accompanying drawings in which:

FIG. 1 illustrates a heat exchange body according to one aspect of the invention;

FIG. 2A illustrates a stack of plates for forming an insert;

FIG. 2B illustrates a Type one Shim

FIG. 2C illustrates a Type two Shim;

FIG. 3 is a perspective view of the stack shown in FIG. 2A.

FIG. 4 is a cross section of the stack in situ;

FIG. 4A is a cross section of a modified stack in situ;

FIGS. 5A and 5B illustrate the handle means applied to the shims;

FIGS. 6A and 6B, 7, 8 and 9 illustrate the handle means in a position of use for each shim type;

FIG. 10A shows an alternative preferred embodiment of shim;

FIG. 10B illustrates a second embodiment of shim with an alternative form of leading edge;

FIG. 11 is a perspective view of a series of shims according to a third embodiment of the invention;

FIG. 12 illustrates a first example of a stacked form of the third embodiment of the invention adapted to receive a catalyst;

FIG. 13 illustrates a second example of a stacked form of the third embodiment of the invention adapted to receive a catalyst;

FIG. 14 is a cross-section of a fourth embodiment illustrating a corrugated insert;

FIG. 15 is an exploded view of the fourth embodiment; and

FIG. 16 is a cross section through a fifth embodiment of the insert according to the invention.

Referring to the drawings in FIG. 1, there is illustrated a simple cross flow reactor according to a first embodiment of the invention. The reactor 10 incorporates removable inserts (not shown) which have been pushed into a plurality of channels 14 for one stream 16. Thus, the reactor provides multiple inlets 20 for a first stream 16 and outlets 22 for the stream. The cooling fluid 24 passes through a plurality of channels 26 to provide the heat exchanger, as is well known. Of course, multi-stream versions are envisaged without departing from the scope of the invention.

In FIG. 2, there is shown an example of shims 28, 30 suitable for use as a removable insert 29. The shims can be of any geometry and size but, typically the flow length is greater than the flow widths. It is desirable that the channel widths and channel wall thicknesses should match for each shim type. Thus when stacked one on another, taller height channels of a given width are formed (see FIG. 3).

In this embodiment, there are shown two types of shim, 28, 30, illustrated in FIGS. 2B and 2C respectively. Both shim types 28, 30 have identical channel widths W and channel wall thickness T (not shown) but have cross braces 31a, 31b which are located differently. When stacked, the Type One and Two shims will be placed alternately within the stack to form a stack of required height, shown in FIG. 2A. The width of the shims will be such that they make a slide in fit with the side walls of the channels and prevent the free bypass of fluid around the insert. Preferably, the retention means is provided to retain the insert within the channels by a mechanical force, for example an interference or push type fit, according to the component type. Alternatively, a spring leaf arrangement can be used to apply the mechanical force, for example see FIG. 4A.

In some embodiments, adjacent inserts could be manufactured from dissimilar materials having differential expansion rates, to encourage an interference fit.

The braces 31a, 31b supporting the channels 33 are offset relative to each other for each shim type 28, 30 so that when stacked one on another, there is always an open path available in order to allow flow to take place along the channels 33. Typically, the shims will be about 0.5 mm thick or less and will be chosen so that when stacked (FIG. 3) the stack height of the shim pack shown in FIG. 2A makes a ‘push fit’ within the channel 14 of the reactor 10. Thus, shims of several reduced thicknesses, for example 0.15 mm, 0.25 mm and 0.5 mm, should be used to provide an accurate stack height, shown in FIG. 4 for a tight fit in the channel 14.

In FIG. 4A the shims 28, 30 have an intervening leaf spring LS to encourage a fit into the channel 14.

As shown in FIGS. 5A and 5B, at either or both end portions each shim 28, 30 will typically have an extension element 38, an open area bounded by a narrow strip 40. These areas are defined by means of narrow cross grooves 42a, 42b typically, 0.5 mm wide and 0.25 mm deep which allow the extensions to be folded out of alignment within the main body of the shim.

Preferably, the extension elements 38 are folded at right angles to the shim such that they do not mask the flow paths, as shown in FIG. 6A and FIG. 6B.

FIG. 7 shows details of the points of entry 39 of a Type One shim 28 and FIG. 8 illustrates the details the points of entry 40 of a Type Two shim 30. Preferably, the cross braces 31 are locally reduced in thickness in order to maximise the flow paths for the catalyst coating process.

By folding the extension elements, there is provided a strengthened area A on which a force can be exerted to push the insert pack for installation in the reactor passageways, shown in FIG. 9, thereby to provide handle means. In some embodiments, the extension elements can be of reduced thickness with respect to the plate.

Conversely, when the need arises to remove the inserts from the reactor, the extensions can be folded back to their original position and used as a location for exerting mechanical loads in order to pull out the pack of shims. Alternatively, one shim can be extracted initially by locating on just one extension. Once removed the other shims will be more readily extracted.

Further embodiments of shim are illustrated in FIGS. 10A and 10B. The shims are similar to those described above and, therefore, like parts have been distinguished with the same reference numeral. Only the differences will be described hereafter.

FIG. 10A illustrates a shim with angled protrusions 50 along the longitudinal edges of the shim. These protrusions are dimensioned such that they provide a good fit between the insert and the side walls of the channel, thereby limiting free bypass of fluid around the insert. The embodiment illustrated comprises protrusions angled in a common direction which can be arranged to function as barbs providing a gripping means to retain the insert. Other embodiments are also envisaged whereby the protrusions are angled in different directions, or simply perpendicular to the longitudinal edges of the shim.

The shim also includes a recess 51 in the extension elements adapted to receive a pulling device (not shown).

This embodiment further comprises apertures 52 which align in stacked condition. The apertures may be punched or etched holes that provide assistance during assembly. The holes may also be used to provide a secondary lock during insertion of the insert.

The extension elements at one end include a protruding portion which is thinner than the main portion. The change in thickness is sharp, providing a stepped transition.

When the shims are stacked and the top and bottom shims in the stack include this feature, the step provides a ‘lead in’ which aids insertion of the insert into the channel.

The embodiment in FIG. 10B comprises leading edges provided with a ‘lead in’ feature for ease of loading into the passageways. In this embodiment the lead in is provided by tapered front ends 45, 47.

The shims are coated with catalyst which can be accomplished by various methods. e.g. by dipping each shim into a solution containing suspended catalyst and then stoving prior to assembling into a stack. More preferably, the shims are assembled into a stack in the order specified to meet the performance requirements and lightly compressed together in a ‘custom designed’ flow fitting. The catalyst suspension liquid is then passed through the channels so that only the working surfaces are wetted by the catalyst. The whole assembly is baked in order to drive off the liquid and leave the catalyst deposited on the working surfaces. The pack could then be removed and inserted into the working reactor. Alternatively, the shims could be assembled into the working reactor prior to the application of catalyst and, when processed, supplied directly to the customer for use as a working reactor.

In order to gain access to the inserts, the headers/tanks of the heat exchanger/reactor are removable, thereby exposing the extensions on the ends of the inserts. Mechanical/hydraulic equipment is used to extract the inserts.

According to a second aspect of the invention, inserts 128, 130, 132 are provided (see FIG. 11) which are similar to those described above, but are used as means to retain solids for catalysts and/or adsorbents.

In FIG. 11, the first approach is used whereby the adsorbent is a pre-formed solid piece 134, e.g. 3-dimensional solid object or in granular form. The first approach is for a solid piece of adsorbent for example forming a rectangular prism. Of course, other types of adsorbent and/or catalyst are provided without departing from the scope of invention. The three types of shims 128, 130, 132 are designed to hold the solid in place whilst providing a free channel 136 (see FIG. 12) through which the fluid can flow and thereby contact and adsorb into the solid.

The shim inserts 128, 130, 132 can be any geometry and size but typically the flow length would be much greater than the flow widths. It is preferred that the channel widths ‘w’ and channel wall thickness ‘t’ should match for each shim type. Thus when stacked one on another, taller height channels of a given width are formed. For example, in this embodiment the shims are typically of the order 0.15 mm to 0.5 mm thick.

Shim Type three 128 consists of only the outer walls, sized such that the solid adsorbent will fit into the gap in the centre of the shim. A number of these shims 128 can be stacked on top of each other to form a channel of the required depth for the solid.

Shim Type four 130 is a supporting shim, upon which Shim Type three 128 and the solid 134 are placed. In this embodiment, it shows ligaments 138 running the length of the shim, providing the support means to hold the solid. The ligaments 138 can include pins 141. By including these pins 141, the solid 134 is held above the ligaments 138 and therefore less of the solid is covered by the ligaments 138. In those embodiments, with longitudinal ligaments 138 there can also be provided latitudinal cross-braces 140 to improve rigidity that may be required for thin ligaments crossing a long length. The ligaments 138 can form any pattern, e.g. longitudinal, latitudinal, diagonal, and is not limited to the pattern illustrated in the drawings. Similarly, the pins 141 can be another shape or cross-sectional profile without departing from the invention.

A final Shim Type three 128 is placed at the base of the stack. The whole assembly (FIG. 12) can then be pushed into the slot in the reactor. It is desirable to have the solid of slightly greater depth than the total of the Type three shims 128 above the Type four shim 130. In this way, the ligaments 138 are pushed downwards and act as a spring, thereby ensuring the top surface of the solid 134 is brought into firm contact with the heat transfer surface of the unit immediately above it.

Alternatively, a solid metal shim, Shim Type five 132, can be placed directly below Shim Type four 130, meaning the ligaments are not deflected downwards, as shown in FIG. 13. This can be beneficial if the pins 140 can be pressed into the solid adsorbent 134, thereby taking up the excess height and ensuring a tight fit into the channel 136.

When a solid metal shim 132 is used, there may need to be apertures 142 positioned to coincide with any latitudinal struts or cross-braces, as shown on Shim Type five 132. These allow the fluid to flow around the ligaments 138 or cross-braces 146 that would otherwise impede its flow.

If the adsorbent is in the form of granules, it is also possible to use the shims as described in the above manner. The struts in Shim Type four 130 would have to be such that the granules could not pass between the gaps and hence remain held above the base of the shims. The granules would fill the space in Shim Type three 128 and then be pushed into the unit.

It is possible to bond the shims together around the edges prior to insertion of the solid. This will aid their insertion into the heat exchanger unit.

In this embodiment, the shims may include folding extension members 138 which are similar to those applied to the first embodiment, as described above to allow their insertion and removal from the unit channels.

A second approach for applying the adsorbent and/or catalyst is to inject it into the structure as a slurry and then dry it to form a porous solid. It may be beneficial to flow the solid in as a slurry then bake it dry.

Shims 130 with the “pin-fin” structure could be assembled with solid top and bottom plates that are not bonded to the pin-fin shims. The slurry can be injected into this structure and dried. Once dry, the bottom plate can be replaced with a Shim Type four 130 as in FIG. 11 and a shim Type three 128 or five 132 to form the base plate as required, thereby providing a flow channel 136 for the fluid. The top plate can be removed before insertion into the unit.

It is desirable to use a system for inserting the solid into the unit after bonding has taken place.

Thus, a second aspect of the invention is a means of using a compact heat exchanger to operate adsorption processes. The small channels and high heat transfer capability of the equipment will provide a means of carrying out adsorption -processes where a fluid has to be brought into contact with a solid and the temperature of the process has to be carefully maintained. In particular it is a means for introducing solid adsorbent into the heat exchanger structure through the use of removable inserts.

A third aspect of the invention relates to an insert 200 provided by a metal sheet 202 folded to form corrugations 204 extending along its axis shown in FIGS. 14 and 15. The removable insert 200 is designed to provide an interference fit within at least one of the flow passages.

In this embodiment, there comprises an insert 200 comprising a first catalyst support 206 and a second catalyst support 208 orientated in a first direction. Intermediate first and second catalysts supports there comprises a single leaf spring, or other suitable resilient biasing means 210 for exerting an outward force against the first and second catalyst supports.

Thus, the catalyst supports 206, 208 are pressed against the upper and lower walls of the passageway 211, 212, shown in FIG. 14.

Turning to the configuration of each catalyst support 206, 208, the configuration can be varied and may include one or more of the following; a fin, machine structure, or etched shim, as illustrated above. The purpose of the support is to provide a base structure to which the catalyst is applied, by one or more of the methods outlined above.

In FIG. 14 there is illustrated a cross section, the construction of the insert 200 within a heat exchanger or chemical reactor. There is shown a first adjacent passageway 214 and a second adjacent passageway 216 separating the reacting passageway 218. Within the reacting passageway 218, spring bars 213 separate adjacent inserts 200.

The resilient biasing means 210 may be formed by a metal sheet which is corrugated and is preferably a single leaf. Alternatively, it may be provided by a stack leaf arrangement, or indeed a coil. The configuration of the resilient biasing means will be configured according to the cavity configuration and catalyst support design structure and is not therefore limited to those examples hereinbefore described.

Referring now to FIG. 16, there is shown a further embodiment of insert in which the bottom few shims of the insert stack are process shims 28, 30, which may or may not contain a catalyst within them. The process fluids will react and produce one or more products. The specific components to be separated are within this stream.

The middle layer consists of a membrane 400 covering the full width of the shim insert. The component to be separated will flow through this membrane 400 possibly driven by a lower pressure above the membrane 400 than below. It is possible that the membrane 400 can sit within a shim in the same manner as the solid adsorbent 134 previously described.

The top layer will consist of a shim 90 or shims that collect the separated component and direct it away from the process fluids. Other channels can be built into the heat exchanger/reactor body to divert the separated component to a specific outlet 91.

The shims 90 for collection of the separated component cannot have open channels at their start and end, distinguishing themselves from the process shims 28, 30 to prevent the process gas directly entering this layer.

An interference fit will be required to hold the shims in position. The fit will have to be such to ensure the majority of the fluids pass down the process layers and leakage around the membrane 400 is minimised.

Various modifications can be incorporated into the invention, without departing from its scope. For example; the resilient biasing means, such as the single leaf may be used within the first embodiment. Alternatively, one or more of the Shims may include corrugations to bias the insert towards the channel wall.

A further modification is that the insert may not be required in every channel; for example, the inserts may be dispensed with to aid heat transfer characteristics.

Any reference to the use of an adsorbent also applies to a solid catalyst, and any reference to a solid refers to a catalyst, an adsorbent or an adsorbent catalyst.

In some embodiments, the inserts are preferentially coated, so as to encourage preferential reaction through the channels, for example the coating may be applied selectively to parts of the insert, to encourage reaction at these parts.

Claims

1. A heat exchanger or chemical reactor comprising a heat exchange body defining a plurality of flow passages defining a Principal flow direction between an inlet and an outlet and a removable insert defining secondary heat exchanger surfaces retained within at least one of the flow passages, by insert retention means, the insert comprising two or more plates, one or more of the plates having elongate passages to define fluid flow channels extending in the principal flow direction, wherein one or more of the plates is provided with a carrier for a catalyst or adsorbent.

2. A heat exchanger or chemical reactor as claimed in claim 1, wherein the one or more plates comprising fluid flow channels includes one or more cross members positioned across the channels.

3. A heat exchanger or chemical reactor as claimed in claim 4, wherein one or more of the plates are of different thicknesses with respect to the other plate or plates in a stack.

4. A heat exchanger or chemical reactor as claimed in claim 1, wherein said insert retention means is provided at least in part by the stack which is slightly greater in height than the height of the fluid passage to provide an interference or push fit.

5. A heat exchanger or chemical reactor as claimed in claim 2 wherein the one or more cross-members are of reduced thickness with respect to the plate.

6. A heat exchanger or chemical reactor as claimed in claim 1, wherein said insert retention means is provided at least in part by gripping means incorporated in the structure of said insert.

7. A heat exchanger or chemical reactor as claimed in claim 6, wherein said gripping means comprises a barbed external surface of said insert, said barbs being angled in a common direction.

8. A heat exchanger or chemical reactor as claimed in claim 1, wherein the insert is provided with a handle means for a user to insert or retract the insert from the heat exchange body.

9. A heat exchanger or chemical reactor as claimed in claim 8, wherein said insert handle means further comprises a recess adapted to receive a pulling device.

10. A heat exchanger or chemical reactor as claimed in claim 8, wherein said insert handle means further comprises a stepped transition in thickness.

11. A heat exchanger or chemical rector as claimed in claim 1, wherein the insert comprises a plurality of stacked plates, each plate having one or more apertures which are aligned in stacked condition.

12. A heat exchanger or chemical reactor as claimed in claim 1, wherein longitudinal edges of said insert comprise protrusions arranged to provide an interference or push fit.

13. A heat exchanger or chemical reactor as claimed in claim 1, wherein the insert comprises a plurality of stacked plates, each plate having one or more slots that define said plurality of flow passages when the plates are stacked.

14. A heat exchanger or chemical reactor as claimed in claim 13, wherein catalyst is retained within the one or more slots.

15. A heat exchanger or chemical reactor as claimed in claim 13, wherein the one or more slots are aligned to form a channel in the stack to receive a catalyst and/or an adsorbent.

16. A heat exchanger or chemical reactor as claimed in claim 15, wherein said catalyst and/or adsorbent is a solid.

17. A heat exchanger or chemical reactor as claimed in claim 16, the stack further comprising one or more support plates having a plurality of support elements to support said solid within said channel.

18. A heat exchanger or chemical reactor as claimed in claim 17, wherein the support elements are provided by ligaments interconnecting one or more pins formed in the plate, the pins providing a raised platform for said solid.

19. A heat exchanger or chemical reactor as claimed in claim 15, wherein the catalyst and/or adsorbent is granular and retained within said slots which are sized to prevent said granules from passing through the slots.

20. A heat exchanger or chemical reactor as claimed in claim 13, wherein the catalyst is coated on to the plates.

21. A heat exchanger or chemical reactor as claimed in claim 1, wherein the insert further comprises a membrane for separating a component of the fluid flow.

22. A shim useful as an insert in a heat exchanger or chemical reactor, the shim having a plurality of channels formed therein, and one or more cross members positioned across said channels.

23. A shim as claimed in claim 22, wherein the cross-members are of reduced thickness with respect to the plate.

24. A shim as claimed in claim 22 further comprising an extension element hingedly connected to the plate and adapted to be folded out of alignment of the body to form handle means.

25. A shim as claimed in claim 24, wherein said extension element further comprises a recess adapted to receive a pulling device.

26. A shim as claimed in claim 25, wherein said extension element comprises a stepped transition in thickness.

27. A shim as claimed in claim 22, wherein the shim comprises a leading edge, which is tapered to aid insertion of the shim into a heat exchange body.

28. A shim as claimed in claim 22, further comprising protrusions along the longitudinal edges of said shim.

29. A shim as claimed in claim 28, wherein said protrusions are angled in a common direction.

30. A shim as claimed in claim 22 further comprising one or more apertures.

31. A shim as claimed in claim 22 further comprising a protruding portion of the extension element that can be adapted to fold out of alignment of the body.

32. (canceled)

33. (canceled)