EP3423773A1

EP3423773A1 - Recuperator, parts of which are manufactured by injection moulding

Info

Publication number: EP3423773A1
Application number: EP17716064.5A
Authority: EP
Inventors: Wessel Bart Veltkamp; Peter Hoogendoorn
Original assignee: Level Holding BV
Current assignee: Level Holding BV
Priority date: 2016-03-01
Filing date: 2017-03-01
Publication date: 2019-01-09
Also published as: NL2016347B1; WO2017150975A1; CN109073336A

Abstract

The invention relates to a recuperator, comprising plates stacked onto each other and extending with their main direction parallel, wherein at least some of the number of plates are provided over at least a substantial part of their surface with profiles comprising side walls which extend mutually parallel and with a component transversely of the main direction of the plates, and channels extending mutually parallel are present between the side walls, wherein each of the side walls lies adjacent on one of its sides to channels of the first type and lies adjacent on its other side to channels of the second type, wherein adjoining plates stacked onto each other are connected at their edges extending parallel to the channels and the plates which are provided with profiles are manufactured by injection moulding. The plates which are provided with a profile preferably comprise side wall pieces extending parallel to the longitudinal direction of the profiles and forming a connection to side wall pieces of adjacent plates.

Description

Recuperator, parts of which are manufactured by injection moulding

The invention relates to recuperators, i.e. heat exchangers which are configured to transfer thermal energy between two fluids which are guided through two series of channels thermally coupled to each other, wherein the two media remain separated.

The invention relates more particularly to a recuperator comprising a number of plates stacked onto each other and extending mutually parallel, wherein at least some of the number of plates are provided over at least a part of their surface with profiles which form channels extending between the plates and wherein the channels present on either side of a plate extend parallel, wherein each of the plates lies adjacent on one of its sides to channels of the first type and lies adjacent on its other side to channels of the second type, and wherein adjoining plates stacked onto each other are mutually connected at their edges extending parallel to the channels.

Such recuperators are known, for instance from EP-A-0 666 973. This document describes a recuperator comprising a number of plates stacked onto each other and extending with their main direction parallel to each other, wherein at least some of the number of plates are provided over at least a substantial part of their surface with profiles comprising side walls which extend mutually parallel and with a component transversely of the main direction of the plates, and channels extending mutually parallel are present between the side walls, wherein each of the side walls lies adjacent on one of its sides to channels of the first type and lies adjacent on its other side to channels of the second type, and wherein adjoining plates stacked onto each other are mutually connected at their edges extending parallel to the channels.

In these prior art recuperators use is made of plates which are provided with profiles and which are manufactured by means of thermoforming. Although thermoforming produces a satisfactory product, it has limitations in respect of material and shape of the channels. Further research has shown that there is a need for a greater freedom in the choice of the shape of the channels and materials, for instance in respect of resistance to aggressive substances and temperatures. The thermoforming further requires a relatively large number of operations, such as extruding of the foil, handling of the rolls of foil, removal of the formed plates from the thermoforming machine, stacking of the plates and forming of a connection between the plates using adhesive, chemically by means of immersion in a mild solvent, or ultrasonic welding. These prior art recuperators also comprise a number of walls which are fastened against the sides of the stack of plates by means of hot melt, since the sides of the plate must be sealed off from the surrounding area.

The object of the invention is to provide a recuperator which obviates the above stated drawbacks. This object is achieved with a recuperator of the above stated type, wherein the plates which are provided with profiles are manufactured by injection moulding.

Many more materials are suitable for injection moulding than are suitable for thermoforming, this increasing the choice of material. The process of injection moulding provides more freedom in respect of the shape of the channels and enables a greater precision.

It is noted that EP-A-2 614 764 describes a recuperator which is assembled from stacked plates, each manufactured by injection moulding. Channels of the same type are however present here on either side of the side walls, since channels of different types are always separated by the plates themselves. No heat transport takes place through the side walls here.

According to a first preferred embodiment, the side walls of the profiles extend substantially transversely of the main plane. This makes the height of these walls as small as possible, which facilitates the injection moulding.

It has further been found attractive for the average distance between the adjoining side walls to be smaller than the width of the side walls.

It has also been found attractive for the thickness of the side walls to be at least a factor of two smaller than the average distance between the side walls. Recuperators can be manufactured with different geometries. There are geometries wherein only plates provided with a profile are applied, but there are also geometries wherein plates provided with a profile are alternated with flat plates. The plates which are provided with a profile and manufactured by injection moulding can be combined with other plates which are provided with a profile and formed by thermoforming, or with flat plates which may or may not be formed by injection moulding.

The invention further relates to a method for manufacturing a recuperator, which recuperator is provided with a number of plates extending mutually parallel, at least some of which are provided over at least a part of their surface with profiles, wherein the profiles are provided with side walls extending with a component transversely of the main direction of the plates and wherein channels extending mutually parallel are present between the side walls, wherein each of the side walls lies adjacent on one of its sides to channels of the first type and lies adjacent on its other side to channels of the second type, wherein adjoining plates stacked onto each other are mutually connected at their edges extending parallel to the channels, and wherein at least some of the plates are manufactured by injection moulding and the thus manufactured plates and plates which may have been manufactured in another way are stacked. In order to make the transfer of the thermal energy between the fluids as great as possible, it is preferred for the plates to be as thin as possible, also in parts of recuperators manufactured by injection moulding. This moreover reduces the use of material. According to a preferred embodiment, the plates which are provided with a profile have a thickness smaller than 500 μιη. For the same reason, it is more preferable to apply even smaller thicknesses, such as smaller than 400 μιη, smaller than 250 μιη, smaller than 150 μιη or smaller than 100 μιη. These smaller thicknesses are made possible by modern injection moulding techniques, such as injecting from the centre of the plate, the use of a series of hot runners, application of a higher pressure such as >1500 bar or > 2000 bar and/or the use of materials with a melt flow index > 120.

According to a further preferred embodiment, the plates which are provided with a profile are manufactured from polypropylene. Polypropylene is a material which can be supplied with a melt flow index greater than 120, while being a material which can readily withstand the aggressiveness of diverse fluids. During the transfer of thermal energy it is attractive if not only the sensible heat is transferred, but also the latent heat. This requires condensation and evaporation alternating over time in a single channel and condensation and evaporation taking place simultaneously in different channels. In order to enhance the evaporation it is preferred for the surface of the plates provided with a profile to have a capillary or hydrophilic structure. This is because the water spreads owing to the hydrophilic structure, so that it can evaporate more effectively. Since the geometry wherein only plates provided with a profile are applied halves the use of material, it is preferred for all plates to be provided with a profile.

In injection moulding it is attractive to place the injection points in the centre of the plate. In order to obstruct the flow of the liquid plastic in the vicinity of the injection points as little as possible, it is preferred to provide the profiled plates and manufactured by injection moulding with at least one distribution strip extending transversely of the longitudinal direction of the profiles, parallel to the main direction of the plate. In combination with the placing of one or more injection points in these strips a better distribution of the plastic is obtained, which can greatly reduce the cycle time.

According to a further preferred embodiment, the profiled plates are provided with one elongate distribution strip extending transversely of the longitudinal direction of the plate, substantially in the centre of the profiles and parallel to the main plane of the plate. The injection point or injection points is or are then placed in this distribution strip.

This same advantage is achieved when during injection moulding the plates are injected in a distribution strip of the plates which lies between the profiles and extends transversely of the profiles.

The recuperator has to be provided with side walls extending parallel to the channels and transversely of the main plane of the plates, since the outermost channels have to be closed off from the surrounding area. It is therefore attractive for the profiled plates to comprise side wall pieces extending parallel to the longitudinal direction of the profiles and forming a connection to side wall pieces of adjacent plates. The side wall pieces of the plates which are provided with profiles and which are stacked onto each other here together form the side walls of the recuperator. These features are difficult to apply in plates manufactured by thermoforming, but they can be readily implemented in plates manufactured by injection moulding. These side wall pieces are preferably arranged on both mutually opposite sides of the plates so that a side wall is created on both sides of the recuperator. It is further possible for the side wall pieces on each of the sides to extend to only one side. In this case the width of the side wall pieces corresponds to the distance between the plates. It is however likewise possible for the side wall pieces to extend to both sides. The width of the side wall pieces amounts here to a part of the overall width, but the sum of the widths of both side wall pieces on one side is equal to the distance between the plates.

The side wall pieces preferably form a form-locking connection to the side wall pieces of adjoining plates. This is otherwise also understood to mean the situation in which, in the absence of side wall pieces in an adjoining plate, the side wall pieces are connected directly to the adjoining plate itself by a form- locking connection. A form- locking connection is understood to mean not only a snap connection, but also other types of connection such as a connection wherein a tongue is moved into a groove and wherein the tongue and the groove have side walls extending in tapering manner at an angle of between 0° and 7° relative to the direction of movement. The material is deformed here during insertion, which results in a wedging action. A form-locking connection makes it easy to mutually connect the plates after stacking without application of adhesive or other alien materials, which could cause problems during reuse.

This embodiment likewise relates to a method wherein the side edges of the plates are provided with side wall pieces and the side edges of the plates are mutually connected by the forming of a form-locking connection. Recuperators have to be provided with connecting pieces in order to carry the fluids from and to the channels. The plates preferably extend into connecting pieces connecting to the recuperator. Connecting pieces are also known as headers in heat exchanger jargon. It is further attractive for the plates to extend into connecting pieces connecting to the recuperator and for the side wall pieces to further extend along at least a part of the edge of the connecting pieces. This also forms the side walls of the connecting pieces at the same time as forming the side walls of the actual recuperator.

As noted above, the plates of actual recuperators extend into the connecting pieces. In the actual recuperators the plates are held at a mutual distance by the profile. No profiles are present at the position of the connecting pieces. In order to also maintain the mutual distance between the plates at the position of the connecting pieces, it is preferred for the plates to be provided with support profiles situated at the position of the connecting pieces, which profiles can otherwise also function as guide for the fluids.

Instead of side walls which are in each case assembled from side wall pieces associated with the plates, it is likewise possible for the recuperator to be provided with side wall plates extending transversely of the main plane of the plates and on either side of the plates.

As already elucidated, a recuperator can be assembled from alternately stacked flat and profiled plates or only from profiled plates. In most cases these plates will be the same profiled plates in each case, although it is likewise possible for the recuperator to be assembled from alternately stacked plates of the first and of the second type, wherein the plates of the first and second type differ from each other.

This embodiment further provides a method wherein plates of a first type and plates of a second type are stacked alternately during stacking.

The above stated measure requires the production of different types of plate. If permitted by the design, it can be attractive for the plates of the second type to correspond to plates of the first type rotated through an angle of 180° over an axis extending parallel to the longitudinal direction of the channels.

This measure likewise provides such a method, wherein the plates of the second type correspond to the mirror image of the plates of the first type and wherein only plates of the first type are stacked during stacking, wherein each second plate is rotated prior to stacking.

In many geometries the channels extend between adjoining plates so that the 'height' of the channels is limited to the distance between two plates. Research has shown that it can be attractive in respect of flow resistance for the height of the channels to be greater. A further embodiment provides for this purpose the measure that channels present in plates lying on each other together form a combined channel. A maximal height of a combined channel, which corresponds to double the distance between two plates, can hereby be obtained.

The above stated research has further shown that the ratio of flow resistance and heat transfer becomes more attractive when the high channel is constricted roughly halfway along its height. A specific embodiment therefore provides the measure that the cross- section of combined channels formed by mutually connecting channels is substantially diabolo-shaped.

Channels with a height in the order of magnitude of the width or channels with a height which is considerably greater than the width are assumed throughout the above. The height is here the measurement of the cross-section of the channel transversely of the main plane of the plates. The manufacture of plates which are provided with a profile for the purpose of forming such channels frequently causes problems during

thermoforming, since these forms release from the relevant moulds with difficulty. In order to prevent this an alternative embodiment proposes that the width of the side walls is smaller than the distance between the adjoining side walls, that the channels have an elongate cross-section and that the main plane of the plates extends substantially in the longitudinal direction of the cross-section of the channels. The largest dimension of the cross-section of the channel hereby extends substantially parallel to the main plane of the plate. This further simplifies releasing of the formed plate from the mould. This is otherwise the case for plates which are manufactured both by means of injection moulding and by means of thermoforming, and for recuperators assembled from such plates. In this configuration transfer of heat inevitably takes place through the plates, this being merely one option in the initially described configuration. The above elucidated feature requires walls extending transversely of the main plane of the plates and forming the end walls of the channels. According to an embodiment, for this purpose the plates are provided with ribs extending substantially transversely of the main plane of the plates, on both sides of the plates and parallel to the longitudinal direction of the channels, these ribs forming end walls of the channels.

In order to complete the end walls, it is preferred for the ribs of adjoining plates to be mutually connected. This is necessary for the ribs on the outer side of the plates to obtain a good seal relative to the surrounding area, but this is not per se necessary for the ribs lying on the inside, although it does make the structure more rigid so that it can better withstand high pressures of the fluids.

The ribs of adjoining plates are preferably mutually connected by means of a form- locking connection. This form-locking connection simplifies assembly, since no adhesive or welding is necessary. The earlier elucidation in this description also applies to this form-locking connection.

Research has shown that the diabolo shape is particularly attractive in respect of the ratio of flow resistance and heat transfer. According to an embodiment, the cross- section of the channels is therefore substantially diabolo-shaped. Diabolo- shaped is understood to mean a substantially rectangular, elongate shape with a distance between the long sides which is smaller in the centre thereof than the distance between the long sides at the ends. The shape can further be provided with rounded corners and the like. Application of the above stated structure, with a main plane of the plates extending substantially in the longitudinal direction of the cross-section of the channels, entails the problem that the connecting pieces cannot be provided with extensions of the plates of the actual recuperator. A specific embodiment provides for this purpose the measure that the recuperator is coupled to connecting pieces which are provided with plates extending transversely of the main plane of the plates of the recuperator.

In order to obtain a good connection between the channels in the actual recuperator and the corresponding spaces of the connecting piece it is preferred for the connecting pieces to be formed into individual units which both connect with their open side to an open side of the recuperator, and for the walls of the channels extending transversely of the main plane of the channels to connect to the positions of the plates of the connecting pieces in the vicinity of the coupling surface between recuperator and the connecting pieces.

As is the case in prior art recuperators and connecting pieces, it is possible to place the separation of the channels wholly in the connecting piece. In the present configuration it is however attractive for some of the number of walls of the channels extending transversely of the main plane of the channels to connect in alignment to the positions of the plates of the connecting pieces at the position of the coupling surface, and for others of the number of walls of the channels extending transversely of the main plane of the channels to connect via a curved part to the positions of the plates of the connecting pieces at the position of the coupling surface. This configuration enables the separation of the channels to be placed partially in the actual recuperator, this simplifying the construction of the connecting pieces.

This embodiment likewise provides a method wherein, following manufacture of the recuperator, the recuperator is provided on both sides with a connecting piece by connecting the connecting pieces at the edges of their fully open surface to the edges of the connecting pieces of the recuperator.

For the purpose of simplifying the assembly it is preferred for the connecting pieces to be connected to the recuperator by means of a form-locking connection, such as a snap connection. The earlier elucidation in this description also applies to this form-locking connection.

This embodiment further provides a method wherein the connecting pieces are connected to the recuperator by means of a form-locking connection. The present invention will be elucidated hereinbelow with reference to the

accompanying figures, in which:

Figure 1 is a schematic perspective view partially in cross-section of a plate according to a first embodiment; Figure 2 is a view of the whole plate, a cross-section of a detail of which is shown in figure 1;

Figure 2A is a cross-sectional view of another detail of the embodiment shown in figures 1 and 2;

Figure 3 is a view of a variant of the plate shown in figure 2;

Figure 4 is a perspective view of a modified version of the first embodiment according to figures 1 and 2;

Figure 4A is a cross-sectional view parallel to the longitudinal direction of the channels of a variant of the embodiment shown in figure 4;

Figure 5 is a view of a recuperator formed by alternate stacking of the plates shown in figures 2 and 3;

Figure 6 is a schematic perspective detail view in cross-section of the recuperator shown in figure 5;

Figure 7 is a schematic perspective view of another variant of the first embodiment; Figure 8 is a schematic perspective view of a plate according to a second embodiment; Figure 9 is a view of the plate shown in figure 8, but which is provided with a part transposing into the header;

Figure 10 is a cross-sectional view of a combination of two plates according to the second embodiment;

Figure 11 is a view of an assembly of two plates as shown in figure 9;

Figure 12 is a schematic perspective view of a part of the recuperator;

Figure 13 is a schematic view of a part of the recuperator; and

Figure 14 is a detail view of the connecting piece for use in the recuperator according to figures 12 and 13.

Figure 1 shows a plate, designated as a whole with 1, as part of a recuperator as shown in figure 5. Plate 1 is provided with protrusions arranged in a regular pattern and forming channels of the first type 3 a. These channels 3 a are surrounded by an end wall 4 and two side walls 5, 6. Channels 3a are open at the position of main plane la of plate 1. The protrusions further form channels 3b of the second type, which are enclosed between side walls 5 and 6 and end walls 7 at the position of the main plane la of plate 1. At the position of the transition between side walls 5, 6 and end walls 4 the plate comprises chamfered portions 8 on the outer side. Plate 1 further comprises ridges 9 protruding at the position of the transition between side walls 5, 6 and end walls 7. Channels 3a and 3b all have substantially the form of a trapezium, which facilitates the release from the mould during manufacture. It is however possible to apply other forms such as that of a rectangle, or a trapezium with the wide side at the end walls. This drawing further shows side wall pieces 10, wherein a channel with a smaller width, i.e. preferably about 0.7 times the width of that of the other channels, is formed between side wall pieces 10 and nearest side wall 5. Other widths are also possible in principle. Side wall piece 10 is further provided on one side with a groove 11 and on the other side with a tongue 12. Arranged on tongue 12 is a linear thickened portion 13a, while a corresponding recess 13b is arranged at a corresponding position in groove 11, these providing for a snap connection during assembly.

When a number of such plates 1 is assembled into a recuperator, a structure as shown in figure 5 is created. It is noted here that plates of different types have been stacked alternately, as will be elucidated below. This figure shows that chamfered portions 8 of a plate 1 fit in ridges 9 of the adjoining plate, so that the relative position of plates 1 in the direction of the main plane of the plates is fixed transversely of the direction of the channel. The same effect is also obtained in side wall pieces 10, the tongues 12 of which are retained by grooves 11 of the subsequent plate, wherein thickened portion 13a and recess 13b fit into each other and provide for the snap connection and additional seal. This figure also shows that channels 3a, 3b in adjoining plates are combined into channels 3 with a largest cross-sectional measurement with double 'height'. This is caused in that plates of different types are stacked alternately. It is likewise possible to obtain channels with a height corresponding to the height of walls 5 and 6 by stacking identical plates onto each other, or to obtain channels with a height corresponding to the height of walls 5 and 6 by stacking different plates onto each other. These channels 3 have a substantially rectangular cross-section, although in figures 1 and 4 the thus resulting channels 3, besides having rounded corners, also have a slightly greater thickness in their centre than at their ends. It is however also possible for channels 3 to have a slightly smaller thickness in their centre than at their ends.

A plate 1 is shown as a whole in figure 2. Plate 1 is provided with side wall pieces 10 extending to both sides and each having a height equal to half the height of the side walls of the channels, so that both side wall pieces together have the same working height as the channels. Plate 1 is further provided with channels 3 at the position of the actual recuperator, while plates 1 comprise at both end surfaces of the actual recuperator a triangular extension 14a, 14b, as is per se known from the prior art. These triangular parts 14a and 14b of the plate form part of the connecting pieces to be formed there, which are also known as headers. These parts 14a, 14b are coupled to extensions 15 of side wall pieces 10, which serve to seal the relevant parts of connecting pieces so that the connecting pieces can fulfil their separating function, as is likewise per se known from the prior art. A snap connection is drawn in the figure, although it is likewise possible to apply a different type of form-locking connection, such as a connection comprising a tapered tongue and groove which will become wedged during insertion owing to the tapered shape. Application of other types of connection, such as by means of adhesive, solvents or ultrasonic welding, are otherwise not precluded. Since side wall pieces 10 extend on both sides of plate 1 in this embodiment, the triangular extensions 14 of the plate are therefore provided on both edges with an extension 15 of the side wall pieces, these extending in opposite directions.

Figure 2A shows a form-locking connection which is attractive in that it requires no additional materials and is thereby simple. One of the parts to be connected 40 is provided here with a tongue 41 which has a tapered shape and which has oblique sides which extend at an angle of between 0° and 7° relative to the direction of movement. The other part to be connected 42 is provided with a groove 43, which is provided with side walls extending at the same or a slightly different angle. When tongue 41 is inserted into groove 43, both parts are deformed slightly, which creates a wedging force between the oblique walls of tongue and groove which will hold together the parts sufficiently firmly. The geometry of tongue and groove must of course be suitable to allow insertion into each other to such an extent that the wedging force can result.

Figure 3 shows a plate 1 which corresponds to the plate of a second type shown in figure 2, which corresponds to the plates of the first type elucidated above but wherein channels 3 have been displaced through half a pitch in order to allow channels 3 a, 3b to connect to each other as shown in figure 5. This indeed results in the channels with a double height, as elucidated above. It is attractive, though not necessary, for the plate of the second type shown in figure 3 to correspond to the plate of the first type, which is shown in figure 2, albeit rotated through 180°. The plate according to figure 3 further differs from that according to figure 2 due to the presence of spacers 16, which keep the triangular extensions 14 of plates 1 at a mutual distance. These spacers 16 further have a guiding function for the fluids flowing through the connecting pieces. It is attractive to arrange spacers 16 such that their effect on the flow affects both fluids, for instance at one of the triangular extensions 14 of each of the plates according to figures 2 and 3. The two plates 1 are preferably the same, and both triangular extensions 14 are provided with spacers 16. If each second plate 1 is rotated during stacking, spacers 16 extend on the other side of plate 1. It is otherwise possible to place all spacers 16 in one plate 1, wherein both triangular extensions 14 are provided on both sides with spacers 16, or to provide both types of plate (so both headers) with spacers 16 on one side. It is even possible to provide one header of both types of plate with spacers 16 on both sides. As already elucidated, according to a preferred embodiment plates 1 are preferably manufactured by injection moulding. In order to be able to perform the injection moulding process as quickly as possible while maintaining a plate of sufficient quality, the injection points must be chosen carefully. They are preferably placed in the vicinity of the centre of plate 1. In order to improve the flow in the vicinity of the injection point or the injection points it is recommended for plate 1 to be flat in the vicinity of the injection points. The modification shown in figure 4 meets this requirement by interrupting profiles 5, 6, 7 in the centre with a distribution strip 18 extending over the whole width of the plate. It is noted that figure 4 shows a modified version of the first embodiment without spacers, the modification according to figure 4 is also possible in the variant provided with spacers. Figure 4 A shows a variant wherein distribution strip 18 has a square cross-section and which shows how profiles 5, 6, 7 gradually transpose into distribution strip 18 in connecting areas 18a. This gradual transition enhances the injection moulding process and further keeps the flow resistance for the fluids at the position of distribution strip 18 as small as possible.

When the plates of the first type according to figure 2 and of the second type according to figure 3 are stacked alternately, a recuperator as shown in figure 5 is created. It is visible here that extensions 15 of side wall pieces 10 of adjoining plates 1 connect to each other. These parts are therefore preferably provided with the same groove and tongue as side wall pieces 10. It is otherwise also possible not to connect the channels to each other, by shifting the adjoining plates through half a pitch.

Figure 6 shows a cross-sectional view of the embodiment shown in figure 5. The profile is here rectangular, although it is apparent that other profiles can also be applied, such as a triangular profile, a trapezoidal profile or such a profile which is provided with rounded corners.

It is however also possible to assemble the recuperator by alternate stacking of flat plates 15 and plates 1 which are provided with a profile. Such a configuration is shown in figure 7. The plates 1 present on both sides of a flat plate 15 can then be of the same type, but can likewise be of a different type. The profiles of the plates 1 which are provided with profiles can further be mutually aligned, although it is also possible to shift the relative position of the plates provided with a profile relative to each other. The presence of the flat plates increases the use of material and thereby the cost price, although a more rigid construction of the recuperator is obtained.

Figures 8-16 relate to a second embodiment. As shown in figure 8, plates 21 do not extend transversely of the longitudinal direction of the cross-section of channels 3, as in the first embodiment, but parallel to the longitudinal direction of this cross-section.

These plates 21 are therefore provided with small ribs 22a which together with the ribs 22b of adjoining plates form the short walls of the channels. As a result, these plates 21 can be easily released from the mould after the moulding process. This is the case for both plates 21 manufactured by means of injection moulding and plates 21

manufactured by means of thermoforming. As shown in figure 8, the ribs 22a, 22b extending on either side of plates 21 are placed alternately in order to obtain the same relative placing of the channels as in the above described embodiment. It is noted that the configuration shown in figure 8 cannot be made in this way by means of thermoforming. In thermoforming, the ribs must have substantially a V-shape and should preferably all extend on one side of the plate. Figure 9 shows a flat plate 21 which results in rectangular channels. In order to obtain channels with a diabolo shape the plates are zigzag- shaped to some extent. As in the previous embodiment, it is possible to have the ribs 22a, 22b extend over the whole width of the short wall of the channel, although it is also possible for them to each extend over only some of the width of this short wall and to be connected to a relevant rib of an adjoining plate.

These parts of ribs 21 can then be mutually connected by a form- locking connection, preferably a snap connection, so that plates 21 are connected to each other. Figure 8 shows only a small part of such a wall. The complete wall extends over the whole height of the recuperator. It is however also possible to assemble such a wall, for instance from parts as shown in figure 8. Such parts can then likewise be connected to each other by a snap connection, which provides the option of adjusting the height of the recuperator. Figure 10 shows a cross-sectional view of this second embodiment. In this embodiment it is not possible to simply form a connection to the connecting pieces, since the channels are mutually offset. In order to facilitate this connection, the rib in the vicinity of the boundary surface between the actual recuperator and the connecting piece is at a part 23a of ribs 22a guided toward an adjoining rib 22b, as shown in figure 9, so that channels 3 come to lie in line at the position of the connecting surface. Such guides 23b are also provided on the other side of plates 21.

Figure 10 shows a cross-sectional view of a combination of two plates 21 which are placed mirror- symmetric ally relative to each other. This figure also shows that plates 21 are provided on their upper and underside with wall pieces 24 which are provided with a form-locking connection such as a snap connection for the purpose of assembling respectively lower wall 24 and an upper wall (not shown in the drawing) of the actual recuperator.

Figure 11 shows two plates 21 as a whole. This figure further shows that the plates are provided with wall pieces 24.

Figure 12 shows an assembly of a number of plates 21, this essentially forming the counterflow portion of the actual recuperator 27. Figure 13 shows a view of the connecting surface of the counterflow portion of a recuperator where it has to be connected to a header. The figure clearly shows the lower wall of the recuperator which is assembled from wall pieces 24, and that the side walls are assembled from side wall pieces 27, 28. Guides 23a and 23b are also visible.

In order to separate the fluid flows flowing through the channels use is made of per se known connecting pieces. Most currently known connecting pieces are formed from extensions of plates of the actual recuperator, as elucidated in the current document on the basis of the first embodiment, but such a combined embodiment appears very difficult, if not impossible, in the configuration of the second embodiment. Use is thus made of individual pairs of connecting pieces, as is otherwise shown in figure 14.

Figure 14 shows a detail of a single connecting piece 30. Connecting piece 30 is provided with plates 31 extending at a mutual distance and having a substantially triangular shape. When connecting pieces 30 are combined with the actual recuperator, these plates 31 are aligned with ribs 22 of the counterflow portion of the recuperator. The distance between plates 31 is therefore equal to the distance between the ribs present on either side of plates 21 of the recuperator, that is equal to half the distance between the ribs 22 lying on the same side of a plate 21, these being the short walls of the channels. Plates 31 are in each case alternately connected on both short sides of the connecting piece by respective strips 32a, 32b. This creates in each case respective openings 33a, 33b on the other short sides, wherein the series of openings 33a lying one above the other are all connected to channels of the first type and the other series of openings 33b lying one above the other are all connected to channels of the second type in the actual recuperator. This corresponds to the connecting pieces as known from the prior art.

These connecting pieces, just as the actual recuperator, can be manufactured by injection moulding and preferably by injection moulding of parts thereof. These parts or segments make it possible to adjust the height of the connecting pieces to the height of the actual recuperator. It is noted here that the width of the connecting piece, just as the height thereof for that matter, is dictated by the dimensions of the actual recuperator.

Claims

1. Recuperator, comprising a number of plates stacked onto each other and extending with their main direction mutually parallel,

- wherein at least some of the number of plates are provided over at least a substantial part of their surface with profiles comprising side walls extending mutually parallel and with a component transversely of the main direction of the plates, and channels extending mutually parallel are present between the side walls;

- wherein each of the side walls lies adjacent on one of its sides to channels of the first type and lies adjacent on its other side to channels of the second type; and

- wherein adjoining plates stacked onto each other are mutually connected at their edges extending parallel to the channels,

characterized in that

the plates which are provided with profiles are manufactured by injection moulding.

2. Recuperator as claimed in claim 1, characterized in that the side walls of the profiles extend substantially transversely of the main plane of the plates.

3. Recuperator as claimed in claim 1 or 2, characterized in that the average distance between adjoining side walls is smaller than the width of the side walls.

4. Recuperator as claimed in claim 2 or 3, characterized in that the thickness of the side walls is at least a factor of two smaller than the average distance between adjoining side walls.

5. Recuperator as claimed in any of the foregoing claims, characterized in that profiled plates and flat plates are stacked alternately.

6. Recuperator as claimed in any of the foregoing claims, characterized in that the profiled plates are provided with at least one elongate distribution strip extending transversely of the longitudinal direction of the profiles, parallel to the main direction of the plate.

7. Recuperator as claimed in claim 6, characterized in that the profiled plates are provided with one elongate distribution strip extending transversely of the longitudinal direction of the plate, substantially in the centre of the profiles and parallel to the main plane of the plate.

8. Recuperator as claimed in any of the foregoing claims, characterized in that the profiled plates comprise side wall pieces extending parallel to the longitudinal direction of the profiles and forming a connection to side wall pieces of adjacent plates.

9. Recuperator as claimed in claim 8, characterized in that the side wall pieces form a form-locking connection to the side wall pieces of adjoining plates.

10. Recuperator as claimed in any of the foregoing claims, characterized in that the plates extend into connecting pieces connecting to the recuperator.

11. Recuperator as claimed in claim 8 or 9 and 10, characterized in that the side wall pieces further extend along at least a part of the edge of the connecting pieces.

12. Recuperator as claimed in claim 10 or 11, characterized in that the plates are provided with support profiles located at the position of the connecting pieces.

13. Recuperator as claimed in any of the foregoing claims, characterized in that the recuperator is assembled from alternately stacked plates of a first and of a second type, wherein the plates of the first and second type differ from each other.

14. Recuperator as claimed in claim 13, characterized in that the plates of the second type correspond to plates of the first type rotated through an angle of 180° over an axis extending parallel to the longitudinal direction of the channels.

15. Recuperator as claimed in claim 13 or 14, characterized in that channels present in plates lying on each other together form a combined channel.

16. Recuperator as claimed in claim 15, characterized in that the cross-section of combined channels formed by mutually connecting channels is substantially diabolo- shaped.

17. Recuperator as claimed in claim 1 or 2, characterized in that the width of the side walls is smaller than the distance between adjoining side walls, that the channels have an elongate cross-section and that the main plane of the plates extends

substantially in the longitudinal direction of the cross-section of the channels.

18. Recuperator as claimed in claim 17, characterized in that the side walls are formed by ribs forming walls of the channels.

19. Recuperator as claimed in claim 18, characterized in that the ribs of adjoining plates are mutually connected.

20. Recuperator as claimed in claim 19, characterized in that the ribs of adjoining plates are mutually connected by means of a form-locking connection.

21. Recuperator as claimed in claim 18, 19 or 20, characterized in that the cross- section of the channels is substantially diabolo-shaped.

22. Recuperator as claimed in any of the claims 17-21, characterized in that the recuperator is coupled to connecting pieces which are provided with plates extending transversely of the main plane of the plates of the recuperator and that the connecting pieces are formed into individual units which both connect with their open side to an open side of the recuperator, and that the walls of the channels extending transversely of the main plane of the channels connect to the positions of the plates of the connecting pieces in the vicinity of the coupling surface between recuperator and the connecting pieces.

23. Recuperator as claimed in claim 22, characterized in that some of the number of walls of the channels extending transversely of the main plane of the channels connect in alignment to the positions of the plates of the connecting pieces (headers) at the position of the coupling surface, and others of the number of walls of the channels extending transversely of the main plane of the channels connect via a curved part to the positions of the plates of the connecting pieces at the position of the coupling surface.

24. Recuperator as claimed in claim 21, 22 or 23, characterized in that the connecting pieces are connected to the recuperator by means of a form- locking connection.

25. Method for manufacturing a recuperator, which recuperator comprising a number of plates extending mutually parallel, at least some of which are provided over at least a part of their surface with profiles, wherein the profiles are provided with side walls extending with a component transversely of the main direction of the plates and wherein channels extending mutually parallel are present between the side walls, wherein each of the side walls lies adjacent on one of its sides to channels of the first type and lies adjacent on its other side to channels of the second type, and wherein adjoining plates stacked onto each other are mutually connected at their edges extending parallel to the channels,

characterized by the steps of manufacturing at least some of the plates by means of injection moulding and stacking the thus manufactured plates, and plates which may have been manufactured in another way, onto each other.

26. Method as claimed in claim 25, characterized in that during injection moulding the plates are injected in a distribution strip of the plates which lies between the profiles and extends transversely of the profiles.

27. Method as claimed in claim 25 or 26, characterized in that the side edges of the plates are provided with side wall pieces and that the side edges of the plates are mutually connected by the forming of a mutual form-locking connection.

28. Method as claimed in claim 25, 26 or 27, characterized in that plates of a first type and plates of a second type are stacked alternately during stacking.

29. Method as claimed in claim 28, characterized in that the plates of the second type correspond to the mirror image of the plates of the first type, and that only plates of the first type are stacked during stacking, wherein each second plate is rotated prior to stacking.

30. Method as claimed in any of the claims 25-29, characterized in that a first wall plate is placed prior to stacking of the plates and a second wall plate is placed after stacking, and that both wall plates are connected with their side edges to the side edges of the plates.

31. Method as claimed in any of the claims 25-30, characterized in that, following manufacture of the recuperator, the recuperator is provided on both sides with a connecting piece by connecting the connecting pieces at the edges of their fully open surface to the edges of the connecting pieces of the recuperator.