WO2022108450A1

WO2022108450A1 - Recuperator with improved channel configuration

Info

Publication number: WO2022108450A1
Application number: PCT/NL2021/050712
Authority: WO
Inventors: Peter Hoogendoorn
Original assignee: Level Holding Ii B.V.
Priority date: 2020-11-20
Filing date: 2021-11-19
Publication date: 2022-05-27
Also published as: NL2026943B1; EP4248161A1

Abstract

Recuperator, comprising: - a number of stacked panels whose main planes extend mutually parallel and which are provided with repeating, mutually parallel profiled sections which form channels which extend between the panels, - wherein one of the sides of each of the panels delimits channels of the first kind and the other side delimits channels of the second kind, - wherein the profiled sections are provided with parts which form side walls of the channels and one directional component of which parts extends transversely to the main plane of the panels, and with parts which extend substantially parallel to the main plane of the panels and which form end walls of the channels, in such a way that each channel comprises two side walls and two end walls, and - wherein the channels have a cross section of a trapezoid, whose dimensions are greater in the direction transverse to the main plane of the panels than in the direction of the main plane of the panels, characterized in that each channel comprises two end walls which are each provided with a protuberance.

Description

Recuperator with improved channel configuration

The invention relates to a recuperator. A recuperator is a heat exchanger which is provided with a plurality of channels which are configured for mutual heat exchange. During operational use of the recuperator, two different flows of fluid are passed through the plurality of channels separately from each other and in a mutually opposite direction, in which case heat is exchanged between the two separate flows via the walls of the channels. Such recuperators are known from various patent documents, including EP-A-0 835 416.

More particularly, the present invention relates to a recuperator of a type which is known per se, comprising:

- a number of stacked panels whose main planes extend mutually parallel and which are provided with repeating, mutually parallel profiled sections which form channels which extend between the panels,

- wherein one of the sides of each of the panels delimits channels of the first kind and the other side delimits channels of the second kind,

- wherein the profiled sections are provided with parts which form side walls of the channels and one directional component of which parts extends transversely to the main plane of the panels, and with parts which extend substantially parallel to the main plane of the panels and which form end walls of the channels, in such a way that each channel comprises two side walls and two end walls, and

- wherein the channels have a cross section of a trapezoid, whose dimensions are greater in the direction transverse to the main plane of the panels than in the direction of the main plane of the panels.

Such recuperators are known from NL-B-2 016 347. In this case, the channels are formed in such a way that the width thereof is significantly smaller than the height thereof, as a result of which a relatively narrow channel has side walls which offer a large lateral contact surface for heat exchange with an adjacent channel.

With this known recuperator, the side walls of the channels extend virtually at right angles to the main plane of the panels. In order to be able to provide the panels with profiled sections, for example by injection-moulding or thermoforming, the side walls of the profiled sections have to extend in a slightly converging way in the direction of the end wall with which they are connected, so that the profiled panel can be released from the mould. In the case of injection-moulding, this required degree of convergence is relatively small, namely 1 to 3 degrees. However, this small degree of convergence has a significant effect on the transfer of heat between the different flows of fluid which are passed through adjacent channels of the recuperator.

More particularly, the Applicant has found that the result of the slight convergence of the side walls of the channels is that the distribution of the flow of fluid through the channels is not evenly distributed and is concentrated in the wider half of the channel, so that the greatest flow rate is achieved there, whereas the flow in the narrower half of the channel is significantly smaller.

In addition, the direction of convergence for laterally adjacent channels alternates, so that the flow-rate distribution between laterally adjacent flows alternates in the same way, with the result that, in adjacent channels, the areas with the greatest flow rate are a relatively large distance apart. This distance is relatively large because it extends diagonally, that is to say both in a transverse direction and in a height direction of the channels. In order for heat exchange to take place between the adjacent flows, a relatively large distance therefore has to be travelled, which greatly reduces the efficiency of the heat transfer compared to a distance which only extends in a transverse direction. In addition, in the case of such a diagonal distance, the utilisation of the large lateral contact surface of the intermediate side wall is sub-optimal.

The present invention endeavours to overcome the above drawbacks by providing a recuperator with a higher efficiency for heat exchange.

In order to achieve this aim, the invention provides, according to a first definition thereof, a recuperator of the abovementioned type, wherein each channel comprises two end walls which are each provided with a protuberance. In this case, the protuberance of a first end wall extends inside the channel, whereas the protuberance of the opposite end wall extends away from the channel (and simultaneously extends into a subsequent adjacent channel). Surprisingly, it has been found that it is possible, on account of the invention, to achieve a very uniform distribution of the flow of fluid in all channels of the recuperator. In particular, this uniform distribution has been observed in the height direction of the channel, as a result of which the area with the largest flow rate extends across both the wider half and the narrower half of the channel.

As a result of the invention, the largest flow rates of two adjacent channels are thus situated a relatively short distance apart (the mutual distance virtually only extends in the transverse direction), as a result of which the efficiency of the recuperator is greatly improved.

For the effect of the invention, it is furthermore advantageous if the trapezoidal cross section of the channels is at least five times greater in the direction transverse to the main plane of the panels than the maximum cross section of the channels in the main plane of the panels. Thus, this ratio of at least 5:1 as a matter of fact only relates to the internal height of the channel compared to the maximum internal width of the channel.

For example, instead of a factor 5, a factor 8, 10, 12, 15 or 20 is used for this ratio.

In order to construct the recuperator according to the invention, the panels first have to be stacked on top of each other to form an operative configuration.

In this connection, it is advantageous if the protuberance comprises two wall sections which extend substantially transversely to the main plane of the panel.

In this connection, it is also advantageous if every end wall comprises two shoulder portions which are provided on opposite sides of the protuberance, wherein the two shoulder portions separately form a lateral connection between the protuberance in the end wall and the two respective side walls which are connected to the end wall.

In particular, it is advantageous, in this connection, if the panels are stacked with the open bottom sides of the profiled sections being situated above the closed top sides of the lower profiled sections.

Each of the above measures helps to enable the profiled sections to engage with each other in a simple manner, with the end walls of a lower panel simply being arranged between two adjoining side walls of an upper panel and vice versa. In addition, the wall sections make it possible to create a small distance between the panels in the height direction, as a result of which some play between adjacent end walls is created in the height direction, so that small variations in the accurate profiled sections of the panels are allowed.

Since there is inevitably some degree of variation in the accurate profiled sections of the panels, not all adjoining shoulder portions of adjacent end walls of adjacent channels will touch each other in the recuperator according to the invention.

In order to further facilitate stacking of the produced panels, it is preferable if the protuberance comprises an end which is formed by an outwardly bent end piece.

It is furthermore advantageous for the recuperator according to the invention if the maximum external width of the protuberance in the end wall is smaller than the minimum external width of the respective side walls to which the end wall is connected.

Thus, there is a difference in width in the profiled section between the maximum external width of the protuberance and the minimum external width of the side walls. This difference in width can be relatively small and may, for example, be of a magnitude which is in the range of the thickness of the panel material. The difference in width may in this case be fractionally larger than the thickness of the material or, on the contrary, be smaller than the thickness of the panel material, for example 40% to 80% of the thickness.

Such relative dimensions of the protuberance are advantageous in order to stack the panels on top of each other in a suitable manner and, in addition, allow some play to be achieved in the lateral direction between adjacent end walls which engage with each other.

Generally, a wall thickness of the panel which is in the range from 0.20 mm to 1 .00 mm is used for a recuperator according to the invention. For injection- moulded panels, a wall thickness in the range from 0.23 to 0.30 mm is particularly preferred.

In order to render the recuperator operational as a heat-exchanger, it is important for both ends of the channels to be provided with connected headers which form separate connections for passing a first flow of fluid and a second, opposite, flow of fluid, respectively, through the relevant channels of the recuperator. Although the advantages of the invention may be achieved using panels which have been produced in various ways, it is preferable if the panels have been manufactured by means of injection-moulding.

Within the context of the present application, the invention may also be described in the form of a second independent claim which is based on a second definition of the invention which relates to an alternative embodiment compared to the recuperator according to the first definition which has been discussed above.

The underlying inventive concept for the invention according to the second definition is the same as that for the invention according to the first definition, particularly with regard to corresponding measures which have been incorporated analogously in both definitions.

The invention according to the second definition should therefore be regarded as an alternative definition of the invention compared to the first definition, the invention according to both definitions fulfilling the legal requirement of unity of invention.

According to a second definition, the invention relates to a recuperator which is configured to exchange heat between two opposite flows of fluid and which is composed of at least the following components: a series of profiled panels which are positioned above one another and which engage in one another, wherein each profiled panel extends in a respective main plane along a length direction and a width direction of the profiled panel, and the main planes of the profiled panels are positioned parallel to each other and above one another, wherein the series of profiled panels are fixedly connected to each other by a covering connecting structure which is coupled to respective outer edges of the profiled panels, wherein each profiled panel is provided with a profiling in the width direction according to a square-wave type pattern of consecutive side walls and end walls which alternate and extend in a length direction, wherein the square-wave type pattern is composed of a periodically repeated base profiled section of a consecutive low end wall, a side wall, a high end wall and a side wall, and the square-wave type pattern defines a height direction of the profiled panel which is at right angles to the main plane of the profiled panel and wherein the difference in height between the high end wall and the low end wall determines the height of the profiled panel, wherein, in the series of profiled panels, the high end walls of a lower profiled panel and the low end walls of an upper profiled panel engage in one another so that adjacent profiled panels together form channels which are delimited by, on the one hand, an end wall and two side walls of the one profiled panel connected to the former, and, on the other hand, an end wall of the other profiled panel, wherein, of two adjacent channels which are positioned directly adjoining each other in the height direction or in the transverse direction, one channel is configured for the passage of a first flow of fluid, and the other channel for the passage of a second, opposite, flow of fluid, characterized in that both the high end wall and the low end wall in the base profiled section are provided with an outward protuberance, as a result of which adjacent profiled panels engage in one another.

Such a recuperator, and the preferred embodiments thereof mentioned below, achieves the same advantageous effects as have already been explained above for the recuperator according to the first definition.

First of all, this recuperator also achieves an improved distribution of the flow of fluid in the height direction of the channels. In addition, this recuperator also makes it possible to still obtain an efficient structure for exchanging heat even with small variations in the dimensioning of the individual profiled panels. For further additional advantages, reference is made to the advantages explained above for the recuperator according to the first definition.

Preferably, it is the case for the recuperator according to the second definition that the engagement of adjacent profiled panels in one another is brought about by the fact that the outward protuberances of a lower profiled panel extend between the adjoining side walls of an upper profiled panel and vice versa.

Thus, the protuberance has a certain insertion depth between the adjoining side walls. This insertion depth contributes to the advantages of the invention. The insertion depth is preferably in the range from 2% to 10% of the height of the channel. With a height of the channel of 8 mm, a suitable insertion depth is, for example, in the range from 0.2 to 0.5 mm.

Furthermore preferably, it is the case for the recuperator according to the second definition that the protuberance comprises two wall sections which extend substantially in the height direction of the profiled panel.

In addition, it is preferable for each end wall of the recuperator according to the second definition to comprise, in the base profiled section, two shoulder portions which are provided on opposite sides of the outward protuberance, wherein the two shoulder portions, separately of each other, form a connection in the width direction between the protuberance in the end wall and the two respective side walls which are connected to the end wall.

According to a further preferred embodiment of the recuperator according to the second definition, the maximum external width of the protuberance in the end wall is smaller than the minimum external width between the respective side walls to which the end wall is connected.

It is advantageous for the recuperator according to the second definition if the side walls of the base profiled section are parallel to each other or in a converging pattern in the direction of the end wall to which both side walls are connected, a preferred range for the degree of convergence being 0.5-3 degrees.

In addition, it is advantageous for the recuperator according to the second definition if, for the base profiled section, the difference in height between low end wall and high end wall is greater than the width between two adjacent side walls, and preferably at least four times greater, more preferably at least five times greater.

For a recuperator according to the invention, for example, a difference in height in the base profiled section is used which is in the range from 6 to 10 mm, and a width between adjacent side walls of 1 .0 mm to 2.5 mm.

For the recuperator according to the second definition, it is, in addition, advantageous if, for a majority of the end walls of adjacent profiled panels which engage in one another, it is the case that the adjoining end walls of a lower profiled panel and an upper profiled panel are positioned at an intermediate distance in the height direction which is greater than half the thickness of the profiled panel itself.

Furthermore, it is advantageous for the recuperator according to the second definition if, for a majority of the protuberances of adjacent profiled panels which engage in one another, it is the case that the mutual distance in the transverse direction between the protuberances of the one profiled panel and the adjoining side walls of the other profiled panel, as well as between the protuberances of the other profiled panel and the adjoining side walls of the one profiled panel, is a small distance which is smaller than half the thickness of the profiled panel itself.

Examples

The invention will be explained below in more detail with reference to the attached figures, in which:

Fig. 1 shows a cross section of a portion of a recuperator according to the prior art;

Fig. 1.1 shows a cross section of another portion of the recuperator according to the prior art;

Fig. 2 shows a cross section of a part of a recuperator according to a preferred embodiment of the invention; and

Fig. 3 shows a cross section of a part of a recuperator according to a preferred embodiment of the invention;

Fig. 4 shows a cross section of a part of a recuperator according to a preferred embodiment of the invention.

Fig. 1 shows a separate cross-layer 1 A of a recuperator 1 according to the prior art. The cross-layer 1 A comprises channels 2A and 2B which lie laterally with respect to each other and extend in a length direction at right angles to this cross section. The channels 2A are of the first kind, as a result of which a first flow of fluid is conducted in a first length direction. Channels 2B of the second kind conduct a second flow of fluid in a second length direction, that is to say opposite to the first flow of fluid.

The recuperator 1 as a whole is composed of a number of cross-layers 1 A which are stacked on top of each other, and one of which is shown here. These cross-layers 1 A are formed by a number of panels 3 which are stacked on top of each other and whose main planes extend mutually parallel, and which are provided with repeating, mutually parallel profiled sections which form channels 2A and 2B which extend the panels. The profiled sections of each panel 3 are composed of a repeating base profiled section which is composed of a side wall 3A, a high end wall 3B, a side wall 3C, and a low end wall 3D. The panels 3 comprising the profiled section thus extend in a transverse direction and a length direction in accordance with the cross-layer 1 A, with the profiled section having a height H. The transverse direction and the length direction of the panel 3 in this case define the main plane of the panel.

By way of illustration of the trapezoidal shape of the channels, the degree to which the side walls of the channels converge in the direction of the end wall to which they are connected has been exaggerated. In practice, a convergence of only 1 -3 degrees is often used for injection-moulded profiled panels. The hatched zones 4 in the respective channels 2A and 2B indicate the areas in which the flow of fluid has the greatest flow rate. It can therefore be deduced directly from the figure that the distance between the adjacent flows of fluid is not merely a lateral distance, in the transverse direction of the channels, but that the distance also has a component in the height direction of the channels.

Fig. 1 .1 shows a more concrete form of a recuperator according to the prior art, in which similar components from Fig. 1 are referred by the same reference numerals. In this case, the degree of convergence between the side walls 3A and 3B is in the usual range of 1 -3 degrees. End wall 3D’ of an upper profiled section and end wall 3B’ of a lower profiled section are also indicated and, together with the walls 3A, 3B, 3C and 3D, delimit the adjacent channels 2A and 2B and therefore effectively form them. The end walls 3B and 3D are slightly bent, but may equally be entirely flat. The flow rates of the respective flows of fluid through the adjacent channels 2A and 2B are represented by grey hues, with the darkest areas indicating the greatest flow rate and being indicated as hatched zones 4.

Fig. 2 shows a cross section of a part of a recuperator 1 according to the invention. Components which are identical to those from Fig. 1 have been denoted by the same numerals. The panel or profiled panel 3 has side walls 3A and 3C with a slight convergence of 1 -3 degrees in the direction of end wall 3B. The same convergence applies conversely to side wall 3A’ and 3C in the direction of end wall 3D. The illustrated base profiled section has a height Hp.

A profiled panel 3’ is positioned above profiled panel 3, which panels engage in one another. On their left-hand outer edges 21 , the two profiled panels 3,3’ are fixedly connected to an outer side panel 20 which forms a covering connecting structure for all profiled panels of the recuperator 1 and thus keeps the profiled panels at a fixed position with respect to each other. Analogously, the opposite right-hand outer edges of the profiled panels (not visible in the figure) are connected to each other by a similar connecting structure.

The end wall 3B is designed to have a protuberance 19 which is composed of two wall sections 9 and an end piece 10. The end piece is slightly bent and thus composed of two pieces 10a and 10b. Furthermore, the end wall also comprises shoulder portions 7 which are provided on opposite sides of the protuberance 19, the two shoulder portions 7 separately from each other forming a lateral connection between the protuberance 19 in the end wall 3B and the two respective side walls 3A and 3C which are connected to the end wall 3B.

The figure shows that the maximum external width of the protuberance 19 in the end wall 3B is smaller than or equal to the minimum internal width between the respective side walls 3A and 3C to which the end wall 3B is connected. In the figure, these widths are virtually identical, so that the thickness of the panel material determines the difference between the maximum external width of the protuberance 19 and the minimum external width of the side walls 3A and 3C.

It can clearly be seen in Fig. 2 that the engagement of adjacent profiled panels 3 and 3’ with each other is achieved by the fact that the outward protuberances 19 of a lower profiled panel extend between the adjoining side walls 3A’ and 3C’ of an upper profiled panel and vice versa. The fact that these protuberances extend between the adjoining side walls changes the distribution of the flow of fluid to a great degree and in such a way that a uniform distribution in the height direction of the channels is achieved.

Fig. 3 shows a similar embodiment of a recuperator to that from Fig. 2, in which the end wall 3B is designed with shoulder portions 7, a protuberance 19 consisting of side pieces 9 and an end piece 10. In this case, the end piece 10 is flat and the shoulder portions 7 extend in a transverse direction which is virtually parallel to the end piece 10. In addition, the external width Bu of protuberance 19 is indicated, and minimum external width Bz of the side walls 3A” and 3C’ of an upper profiled panel. The insertion depth dl is indicated as the degree to which the protuberance 19 extends between the adjoining side walls 3A’ and 3C’ in the height direction.

Both in Fig. 2 and in Fig. 3, the high end walls 3B of a lower panel and low end walls 3D’ of an upper panel are shown as engaging in one another, wherein: for a majority of the end walls 3B and 3D’ of adjacent profiled panels 3 and 3’ which engage in one another, it is the case that the mutually adjoining end walls 3B and 3D’ of an upper and lower profiled panel 3 and 3’ are positioned at an intermediate distance in the height direction which is greater than half the thickness of the profiled panel itself, and for a majority of the protuberances 19 of adjacent profiled panels 3 and 3’ which engage in one another, it is the case that the intermediate distance in the transverse direction between the protuberances 19 of the one profiled panel 3 and the adjoining side walls 3A’ and 3C’ of the other profiled panel 3’, as well as between the protuberances 19 of the other profiled panel 3’ and the adjoining side walls 3A and 3C of the one profiled panel 3, is a small distance which is smaller than half the thickness of the profiled panel itself.

The distances in the transverse direction and in the height direction mentioned above as the preferred embodiment of the recuperator according to the invention, provide play between panels which are positioned above one another and engage in one another. As a result thereof, it is possible to allow small deviations in the dimensioning of the panels positioned above one another.

Fig. 4 shows a recuperator according to the invention which is designed in a similar way to that in Fig. 2, and wherein similar components are denoted by identical reference numerals. The flow rates of the respective flows of fluid through the adjacent channels 2A and 2B are represented by grey hues, with the darkest areas indicating the greatest flow rate and being indicated as hatched zones 4. Compared to Fig. 1.1 , which represents the prior art, it can clearly be seen that the recuperator according to the invention achieves a very uniform distribution of the flow of fluid in the height direction of the channels. Thus, the invention makes a highly satisfactory, optimum exchange of heat possible between adjacent channels 2A and 2B. The above examples only serve as explanation of the invention and the legal definition of the invention is only determined by the claims. The various measures which are mentioned in the examples may be combined separately from each other and are thus included in the definition of the invention.

Claims

1. Recuperator, comprising:

- wherein the channels have a cross section of a trapezoid, whose dimensions are greater in the direction transverse to the main plane of the panels than in the direction of the main plane of the panels, characterized in that each channel comprises two end walls which are each provided with a protuberance.

2. Recuperator according to Claim 1 , characterized in that the trapezoidal cross section of the channels is at least five times greater in the direction transverse to the main plane of the panels than the maximum cross section of the channels in the main plane of the panels.

3. Recuperator according to one of the preceding claims, characterized in that the protuberance comprises two wall sections which extend substantially transversely to the main plane of the panel.

4. Recuperator according to one of the preceding claims, characterized in that each end wall comprises two shoulder portions which are provided on opposite sides of the protuberance, wherein the two shoulder portions separately form a lateral connection between the protuberance in the end wall and the two respective side walls which are connected to the end wall.

5. Recuperator according to one of the preceding claims, characterized in that the panels are stacked with the open bottom sides of the profiled sections being situated above the closed top sides of the lower profiled sections.

6. Recuperator according to one of the preceding claims, characterized in that the protuberance comprises an end which is formed by an outwardly bent end piece.

7. Recuperator according to one of the preceding claims, characterized in that the maximum external width of the protuberance in the end wall is smaller than the minimum external width of the respective side walls to which the end wall is connected.

8. Recuperator according to one of Claims 4-7, characterized in that not all adjoining shoulder portions of adjacent end walls of adjacent channels touch each other.

9. Recuperator which is configured to exchange heat between two opposite flows of fluid and which is composed of at least the following components: a series of profiled panels which are positioned above one another and which engage in one another, wherein each profiled panel extends in a respective main plane along a length direction and a width direction of the profiled panel, and the main planes of the profiled panels are positioned parallel to each other and above one another, wherein the series of profiled panels are fixedly connected to each other by a covering connecting structure which is coupled to respective outer edges of the profiled panels, wherein each profiled panel is provided with a profiling in the width direction according to a square-wave type pattern of consecutive side walls and end walls which alternate and extend in a length direction, wherein the square-wave type pattern is composed of a periodically repeated base profiled section of a consecutive low end wall, a side wall, a high end wall and a side wall, and the square-wave type pattern defines a height direction of the profiled panel which is at right angles to the main plane of the profiled panel and wherein the difference in 15 height between the high end wall and the low end wall determines the height of the profiled panel, wherein, in the series of profiled panels, the high end walls of a lower profiled panel and the low end walls of an upper profiled panel engage in one another so that adjacent profiled panels together form channels which are delimited by, on the one hand, an end wall and two side walls of the one profiled panel connected to the former, and, on the other hand, an end wall of the other profiled panel, wherein, of two adjacent channels which are positioned directly adjoining each other in the height direction or in the transverse direction, one channel is configured for the passage of a first flow of fluid, and the other channel for the passage of a second, opposite, flow of fluid, characterized in that both the high end wall and the low end wall in the base profiled section are provided with an outward protuberance, as a result of which adjacent profiled panels engage in one another.

10. Recuperator according to Claim 9, wherein the engagement of adjacent profiled panels in one another is brought about by the fact that the outward protuberances of a lower profiled panel extend between the adjoining side walls of an upper profiled panel and vice versa.

11 . Recuperator according to one of Claims 9-10, wherein the protuberance comprises two wall sections which extend substantially in the height direction of the profiled panel.

12. Recuperator according to one of Claims 9-11 , wherein, in the base profiled section, each end wall comprises two shoulder portions which are provided on opposite sides of the outward protuberance, wherein the two shoulder portions, separately of each other, form a connection in the width direction between the protuberance in the end wall and the two respective side walls which are connected to the end wall.

13. Recuperator according to a of the claims 9-12, wherein the maximum external width of the protuberance in the end wall is smaller than the minimum external width of the respective side walls to which the end wall is connected. 16

14. Recuperator according to one of Claims 9-13, wherein the side walls of the base profiled section are parallel to each other or in a converging pattern in the direction of the end wall to which both side walls are connected, a preferred range for the degree of convergence being 0.5-3 degrees.

15. Recuperator according to one of Claims 9-14, wherein, for the base profiled section, the difference in height between low end wall and high end wall is greater than the width between two adjacent side walls, and preferably at least four times greater, more preferably at least five times greater.

16. Recuperator according to one of Claims 9-15, wherein, for a majority of the end walls of adjacent profiled panels which engage in one another, it is the case that the adjoining end walls of a lower profiled panel and an upper profiled panel are positioned at an intermediate distance in the height direction which is greater than half the thickness of the profiled panel itself.

17. Recuperator according to one of Claims 9-15, wherein, for a majority of the protuberances of adjacent profiled panels which engage in one another, it is the case that the mutual distance in the transverse direction between the protuberances of the one profiled panel and the adjoining side walls of the other profiled panel, as well as between the protuberances of the other profiled panel and the adjoining side walls of the one profiled panel, is a small distance which is smaller than half the thickness of the profiled panel itself.

18. Recuperator according to one of the preceding claims, characterized in that both ends of the channels are provided with connected headers which form separate connections for passing a first flow of fluid and a second, opposite, flow of fluid, respectively, through the relevant channels of the recuperator.

19. Recuperator according to one of the preceding claims, characterized in that the panels or profiled panels are manufactured by means of injectionmoulding.