EP0208042A1 - Thermoformed sheet for a gas-gas plate heat exchanger, and resulting heat exchanger - Google Patents

Abstract

The thermoformed sheet (1) consists of a vessel (40) in which parallel plates (20) are stacked, separated from each other by lateral spacers. The plates have pointed zones (8, 9) at their ends fitted with elements (11, 12) for alternately closing one of the two sides of the point. The vessel also has walls (45 - 48) connected in a gastight manner to the points at the ends of the plates so as to form separate channels for the entrance or exit of the gases flowing as counter- currents in the alternate spaces formed by the plates. The thermoformed sheet consists of a set of identical rows of elongated units (2a, 2b, 2c, 2d) with edges folded on one side or the other of the sheet. Each unit consists of two parallel longitudinal edges (3a, 4a; 3b, 4b; 3c, 4c; 3d, 4d) by which it is connected to the adjacent units to form a row. The sheet is terminated by two pointed ends (8a, 9a; 8b, 9b; 8c, 9c; 8d, 9d) by which the units of a row are connected to the units of the next row. The intermediate zones (13, 14, 15, 16, 17) between these rows form recesses alternately on one side and the other of the sheet (1). <IMAGE>

Description

The present invention relates to gas / gas plate heat exchangers and more particularly to a thermoformed sheet making it possible to produce plates for such exchangers.

Plate heat exchangers are used in particular for reheating the fresh air entering a building by the stale air which is extracted therefrom, and enable heating savings to be made.

The present invention proposes to allow the production in large quantities and economically of gas / gas plate exchangers to meet the energy saving needs.

There are already known gas / gas plate heat exchangers of the type comprising an enclosure in which are stacked parallel plates, spaced from one another by lateral spacing means, these plates comprising at their ends zones in the shape of a point. provided with elements for alternately closing one of the two sides of the point, the enclosure further comprising walls which are tightly connected to the points of the ends of the plates so as to form separate conduits for supplying or leaving gases which flow against the current in alternating spaces formed by the plates.

Exchangers of this type are described in particular in patents FR 1 272 343 and FR 2 315 674. These exchangers however use plates of complex shape whose manufacture is difficult, which in practice prevents large-scale production.

The present invention aims to overcome these drawbacks by providing a simple and economical sheet for producing plates for heat exchangers.

The sheet according to the present invention is characterized in that it comprises a series of identical rows of elongated patterns with folded edges on one side or the other of the sheet, each pattern comprising two parallel longitudinal edges by which it is connected to the adjacent patterns to form a row and ending in two point ends by which the patterns of one row connect to the patterns of the next row, the intermediate zones existing between these rows projecting alternately from one side and from the other of the sheet.

The sheet according to the present invention is produced by thermoforming, in particular by continuous thermoforming using a mold of length equal to that of the repeating part. It can also be performed sheet by sheet using a conventional machine with a mold large enough to contain a sufficient number of rows.

The sheets according to the invention are advantageously made of thermoplastic material and for example of polyvinyl chloride.

The plates used to make a heat exchanger are obtained by cutting each pattern or a set of patterns inscribed in a rectangle at the level of the connection zones of the patterns in the same row and at the edges of the intermediate zones existing between the rows.

Thus, by the choice of cutting, it is possible to obtain plates of a size adapted to the size of the desired exchanger and therefore to produce exchangers corresponding to very varied gas flow rates.

This cutting can be carried out directly at the outlet of the thermoforming machine.

In a preferred embodiment of the present invention, the sheet has patterns whose parallel longitudinal edges are folded on the same side of the sheet. To make an exchanger according to the invention, these patterns or a set of these patterns are stacked by separating them with flat sheets.

In another embodiment of the present invention, the sheet has patterns, the longitudinal edges of which are folded over on the side of the sheet where the contiguous intermediate zones project. Thus, the longitudinal edges in a row are alternately folded over on one side and on the other of the sheet in phase with the edges of the intermediate zones.

Furthermore, the use of thermoforming to produce the sheets according to the present invention makes it possible to manufacture sheets having roughness particularly studied to create turbulence in the gases. These turbulences are interesting because they increase the efficiency per square meter of exchange surface.

Likewise, the sheet can receive, by thermoforming, bosses intended to maintain the spacing of the sheets despite the pressure difference which may prevail between the two gas circuits.

The invention is set out below in more detail with the aid of drawings representing only embodiments.

• la Fig. 1 est une vue de dessus d'une feuille selon l'invention dans laquelle la limite des parties en creux est représentée par des traits pointillés;
• la Fig. 2 est une vue en perspective des élé­ments d'un empilage comprenant des motifs de la feuille représentée sur la Fig. 1 destiné à constituer un échan­geur de chaleur;
• la Fig. 3 est une vue analogue à la Fig. 2 mais après assemblage;
• la Fig. 4 est une vue de dessus en coupe d'un échangeur de chaleur comprenant un empilage selon la Fig. 3;
• la Fig. 5 est une vue de dessus en coupe d'une partie d'un échangeur comprenant un ensemble de motifs de la feuille représentée sur la Fig. 1;
• la Fig. 6 est une vue de dessus d'une autre feuille selon l'invention dans laquelle les limites des parties en creux sont représentées en traits pointillés;
• la Fig. 7 est une vue en perspective des élé­ments d'un empilage comprenant des motifs de la feuille représentée sur la Fig. 6;
• la Fig. 8 est une vue analogue à la Fig. 7 mais après assemblage;
• la Fig. 9 est une vue de dessus en coupe d'un échangeur de chaleur comprenant un ensemble de motifs de la feuille représentée sur la Fig. 6;
• la Fig. 10 est une vue partielle en coupe sui­vant 10-10 de la Fig. 9;
• la Fig. 11 est une vue de dessus d'un motif pré­sentant des gaufrages;
• les Fig. 12, 13 et 14 sont des coupes respecti­vement selon 12-12, 13-13 et 14-14 de la Fig. 11.

In these drawings:

• Fig. 1 is a top view of a sheet according to the invention in which the limit of the hollow parts is represented by dotted lines;
• Fig. 2 is a perspective view of the elements of a stack comprising patterns of the sheet shown in FIG. 1 intended to constitute a heat exchanger;
• Fig. 3 is a view similar to FIG. 2 but after assembly;
• Fig. 4 is a top view in section of a heat exchanger comprising a stack according to FIG. 3;
• Fig. 5 is a top view in section of a part of an exchanger comprising a set of patterns of the sheet shown in FIG. 1;
• Fig. 6 is a top view of another sheet according to the invention in which the limits of the hollow parts are shown in dotted lines;
• Fig. 7 is a perspective view of the elements of a stack comprising patterns of the sheet shown in FIG. 6;
• Fig. 8 is a view similar to FIG. 7 but after assembly;
• Fig. 9 is a top view in section of a heat exchanger comprising a set of patterns of the sheet shown in FIG. 6;
• Fig. 10 is a partial sectional view along 10-10 of FIG. 9;
• Fig. 11 is a top view of a pattern having embossings;
• Figs. 12, 13 and 14 are sections respectively according to 12-12, 13-13 and 14-14 of FIG. 11.

Sheet 1 shown in FIG. 1 is a sheet of thermoformed thermoplastic material. It comprises in the longitudinal direction of the sheet a series of identical rows of four patterns 2a, 2b, 2c and 2d.

Each of the patterns of a row has the shape of a hexagon elongated in the longitudinal direction of the sheet 1 and comprises two longitudinal parallel edges of the same height folded at right angles to the top of the sheet 1, respectively 3a and 4a, 3b and 4b, 3c and 4c, 3d and 4d.

The edges 4a and 3b, 4b and 3c, 4c and 3d are connected by narrow longitudinal zones respectively 5ab, 5bc, 5cd which are parallel to the plane of the sheet 1. As for the lateral longitudinal edges 3a and 4d they are provided with edges respectively 6 and 7 which are parallel to the plane of the sheet.

Each of these patterns ends in end zones 8a and 9a, 8b and 9b, 8c and 9c, 8d and 9d respectively, which have the shape of an isosceles triangle and which thus give each pattern the shape of a elongated hexagon.

The patterns of the same row are connected by the tips 10a, 10b, 10c, 10d of the end zones 8a, 8b, 8c, 8d to the identical patterns of the next row.

Each end zone such as 8a, 8b, 8c, 8d has an edge 11a, 11b, 11c, 11d folded at right angles towards the top of the sheet and an edge 12a, 12b, 12c, 12d folded at right angles towards the below the sheet. These edges have the same height as the longitudinal edges such as 3a and 4a. In a row, the folded edges above and below are arranged so that the folded edges on the same side are adjacent. Thus the edges 12a and 12b folded down are adjacent. Intermediate zones 13, 14, 15, 16 and 17 are thus obtained between two successive rows which project alternately above and below the sheet. The zones 13 and 17 which are at the edge of the sheet have the shape of an isosceles triangle, while the other intermediate zones have the shape of a rhombus.

There is shown in FIG. 2 elements making it possible to constitute a stack for producing a heat exchanger according to the invention.

These elements comprise on the one hand thermoformed plates 20 obtained from patterns on sheet 1 and on the other hand flat plates 21.

Each plate 20 is obtained by cutting the sheet 1 longitudinally in the middle of the narrow longitudinal zones such as 5, 6, 7 so as to form ledges 22 and 23 parallel to the plane of the sheet and adjacent respectively to the longitudinal edges 3 and 4 thus that at the end zones 8 and 9 in leaving edges 24 and 25 parallel to the plane of the sheet, of the same width as edges 22 and 23 and respectively adjacent to edges 11 and 12 which are one folded above the sheet and the other folded below of the sheet.

The flat plates 21 have a shape corresponding in projection to the shape of the plates 20.

To assemble the thermoformed plates 20 and the flat plates 21, as shown in FIG. 3, the outward facing parts of the sheet of edges 22, 23 and 24 are coated with glue on a first plate 20, a flat plate 21 is applied, then a second plate 20 is applied, including all the edges 25, 24, 22 and 23 have been glued and the stacking continues. To glue polyvinyl chloride sheets, glues based on polyvinyl chloride containing organic solvents can be used in particular.

As a variant, it is also possible to heat seal the edges of the thermoformed plates with the flat plates.

The stack thus obtained is placed, as shown in FIG. 4, in an enclosure 40 in the shape of a rectangular parallelepiped. This enclosure 40 includes conduits 41 and 42 for entering and leaving a first gas and conduits 43 and 44 for entering and leaving a second gas. These conduits are connected to the vertical longitudinal faces 45 and 46, in the vicinity of the vertical end faces 47 and 48. The sealing of the two gas circuits is ensured by vertical seals 49 and 50 which are arranged between the walls 47 and 48 and the tips 10 of the stacking plates, vertical seals 51 and 52 which are arranged between the wall 46 and the ends of the edges 4, as well as horizontal seals not shown.

The first gas (path shown in dotted lines) for example enters via line 41 and passes between a on two of the passages delimited by the plates 20 and 21, namely the passages delimited between a plate 21 and a plate 20 disposed above and exiting through the conduit 42.

The second gas (continuous line path) enters through a conduit 43, passes between the other passages delimited by the plates, namely the passages delimited between a plate 20 and a plate 21 disposed above and exits through the conduit 44.

In these passages, the second gas circulates against the current of the first gas which circulates in the other passages.

The heat exchanger shown in FIG. 5 comprises a stack of a set of patterns of the sheet shown in FIG. 1. In the case shown, the sheet is used in its full width and the assembly comprises several rows of patterns, for example three rows of four patterns. It goes without saying that one can also obtain heat exchangers of different sizes by cutting a different number of rows, as well as by cutting the sheet to obtain a smaller number of patterns in a row.

To make the exchanger shown in FIG. 5, the sheets cut from the sheet shown in FIG. 1 are assembled as described for stacking a plate comprising a single pattern, that is to say by intercalating between them flat sheets of the same size and by gluing the flanges surrounding the patterns of the thermoformed sheet to the flat sheets .

All of the stacked sheets are placed in an enclosure 60 in the shape of a rectangular parallelepiped.

At the ends of the stack there are vertical walls 61 connected in leaktight manner to the tips 10 of the terminal patterns to form separate spaces such as 62 and 63 respectively for supplying a first gas and leaving a second gas.

As in the case of FIG. 4, the first gas (path shown in dotted lines) passes through the passages delimited between a flat sheet and a thermoformed sheet 1 disposed above, while the second gas (path shown in solid lines) flows against the current in the passages delimited between a thermoformed sheet 1 and a flat sheet arranged above.

There is shown in FIG. 6 another thermoformed sheet 101 according to the invention.

Like sheet 1, sheet 101 comprises in the longitudinal direction a series of identical rows of four patterns respectively 102a, 102b, 102c, 102d.

Each of the patterns of a row has the shape of a hexagon elongated in the longitudinal direction of the sheet and comprises two longitudinal parallel edges of the same height folded at right angles, one towards the top of the sheet (103a, 103b, 103c, 103d), the other towards the bottom of the sheet (104a, 104b, 104c, 104d).

The edges 104a and 104b, on the one hand, and 104c and 104d, on the other hand, are juxtaposed and are connected by narrow longitudinal zones 105 and 106 respectively which are parallel to the plane of the sheet and below it this.

The edges 103b and 103c are juxtaposed and are connected by a narrow longitudinal zone 107 which is parallel to the plane of the sheet and above it.

As for the lateral edges 103a and 103d, they are provided with flanges 108 and 109 respectively.

Each of the patterns 102a, 102b, 102c, and 102d ends in end zones respectively 110a and 111a, 110b and 111b, 110c and 111c, 110d and 111d similar to the end zones 8a and 9a, 8b and 9b, 8c and 9c, and 8d and 9d of sheet 1 of FIG. 1.

The patterns of the same row are connected by their points as in the case of sheet 1 of the Fig. 1 by delimiting between them intermediate zones 112, 113, 114, 115 and 116 analogous respectively to intermediate zones 13, 14, 15, 16 and which project alternately above and below the sheet 101.

There is shown in FIG. 7 elements making it possible to constitute a stack for another heat exchanger according to the invention.

These elements include a series of identical thermoformed plates 120 and 121, one of which has simply been rotated 180 ° around an axis perpendicular to the plane of the plate. These plates are obtained by cutting the patterns from the sheet 101 similar to cutting the plates 20 from the sheet 1.

These plates 120 and 121 are provided with a longitudinal edge 122 and two end edges 123 and 124, these edges being respectively adjacent to the edge 103 and to the two end edges 125 and 126 which are folded over the plane. of the sheet, and being themselves parallel to the plane of the sheet.

Similarly, the plates 120 and 121 include a longitudinal edge 127 and two end edges 128 and 129, these edges being respectively adjacent to the longitudinal edge 104 and to the end edges 130 and 131, which are folded below the plane. of the sheet, and being themselves parallel to the plane of the sheet.

The plates 120 and 121 are assembled as shown in FIG. 8 by gluing the outward facing parts of the sheet of flanges 122, 123, 124, 127, 128 and 129.

Alternatively, these edges can also be heat sealed.

The stack thus obtained can be placed in an enclosure similar to that shown in FIG. 4 with vertical seals at the points of the plates and seals between flanges 123,122,124 of the upper plate and the enclosure and between the flanges 128,127,129 of the lower plate and the enclosure.

The heat exchanger shown in FIG. 9 comprises a stack of a set of patterns of the sheet shown in FIG. 6. In the case shown, the sheet 101 is used in its full width and the assembly includes several rows of patterns. The sets are stacked after gluing and rotation of a set of two by 180 ° around an axis perpendicular to the plane of the sheets. The stack obtained is placed in an enclosure 160 provided with gas inlet and outlet conduits as in the case of FIG. 5.

As shown in Fig. 10 the stack obtained delimits a succession of passages comprising alternately a first layer with a double passage 130 and two passages 131 and 132 and a second layer with two double passages 133 and 134. The first gas passes into the first layer and the second gas in the second layer.

There is shown in FIG. 11 a pattern 201 of a thermoformed sheet according to the invention which has embossings on its surface.

Pattern 201 is analogous to pattern 2 of sheet 1 and includes longitudinal edges 202 and 203, as well as end edges 204 folded over the top of the sheet and end edges 205 folded below the sheet. . The edge 205 is thus adjacent to the entrance to the upper passage, while the edge 204 is adjacent to the exit from the lower passage. In the vicinity of the exit from the lower passage, the plate 201 has a rib 206 projecting towards the underside of the sheet, substantially in the middle of the end half-half and at an angle of approximately 70 ° relative to the edge 204 in turning from the tip.

In the vicinity of the entrance to the upper passage, the plate 201 has a rib 207 similar to the rib 206, but projecting towards the top of the sheet.

These ribs 206 and 207 serve to guide the gas flows by distributing them over the entire surface of the plates.

The central zone of the plate 201 also comprises a series of zones 208 having a transverse embossing.

These areas 208 transversely include a succession of bumps 209 and recesses 210 relative to the median plane of the sheet. All of the bumps, hollows and intermediate zones without embossing makes it possible to obtain turbulence favorable to heat exchange.

The main advantages of the present invention are as follows.
- it provides high yields (greater than 70%) as calculated according to AFNOR E 51 702 standard;
- a single mold of reduced dimensions, therefore inexpensive, is sufficient to make all the sizes in the range;
- It is possible to make the sheets of thermoplastic material, which further reduces the cost of tooling compared to that required for making with metal sheets;
- thermoforming also makes it possible to economically produce on the sheet forms of an infinite variety for quite diverse purposes such as, for example:
. create turbulence to increase efficiency,
. keep the spacing of the sheets constant using bosses,
. guide the flows so as to distribute them as uniformly as possible in the passage section. The flow guides can have any shape, for example curved, if desired. The only limit is that the sheet can be removed from the mold after thermoforming.

Claims (7)

1. Thermoformed sheet (1; 101) for gas / gas plate heat exchanger of the type comprising an enclosure (40; 60) in which are stacked parallel plates, spaced from each other by lateral spacing means, these plates comprising at their ends zones in the shape of a point provided with elements for alternately closing one of the two sides of the point, the enclosure further comprising walls which are tightly connected to the points of the ends of the plates so as to form separate gas supply or outlet conduits which flow against the current in alternating spaces formed by the plates, this sheet being characterized in that it comprises a series of identical rows of elongated patterns (2a, 2b, 2c , 2d; 102a, 102b, 102c, 102d) with folded edges on either side of the sheet, each pattern comprising two parallel longitudinal edges (3a, 4a; 3b, 4b; 3c, 4c; 3d, 4d ; 103a, 104a; 103b, 104b; 103c, 104c; 103d, 104d) by which it is connected to the adjacent patterns to form a row and ending in two pointed ends (8a, 9a; 8b, 9b; 8c, 9c; 8d, 9d; 110a, 111a; 110b, 111b; 110c, 111c; 110d, 111d) by which the patterns of a row are connected to the patterns of the next row, the intermediate zones (13,14,15,16,17; 112, 113,114,115, 116) existing between these rows projecting alternately from one side and the other of the sheet (1; 101). 2. Sheet according to claim 1, characterized in that all the longitudinal edges (3a, 4a; 3b, 4b; 3c, 4c; 3d, 4d) of the patterns are folded on the same side of the sheet (1). 3. Sheet according to claim 1, characterized in that the longitudinal edges (103a, 104a; 103b, 104b; 103c, 104c; 103d, 104d) of the patterns are folded on the side of the sheet where the contiguous intermediate zones (112, 113, 114, 115, 116) protrude. 4. Sheet according to any one of the preceding claims, characterized in that the ends of the patterns (8a, 9a; 8b, 9b; 8c, 9c; 8d, 9d; 110a, 111a; 110b, 111b; 110c, 111c; 110d , 111d) have the shape of an isosceles triangle. 5. Sheet according to any one of claims 1 to 4, characterized in that each pattern comprises embossings. 6. Gas / gas plate heat exchanger of the type comprising an enclosure (40; 60) in which are stacked parallel plates, spaced from each other by lateral spacing means, these plates comprising at their ends zones in point form provided with elements for alternately closing one of the two sides of the point, the enclosure further comprising walls which are tightly connected to the points of the ends of the plates so as to form separate conduits for supplying or outlet of the gases which flow against the current in alternating spaces formed by the plates, characterized in that it comprises one or more stacks of plates (20) obtained by cutting out each pattern or a set of patterns inscribed in a rectangle of a sheet (1) according to claim 2, these plates (20) being separated by planar sheets (21). 7. Gas / gas plate heat exchanger of the type comprising an enclosure (40; 60) in which are stacked parallel plates, spaced from one another by lateral spacing means, these plates comprising at their ends zones in point form provided with elements for alternately closing one of the two sides of the point, the enclosure further comprising walls which are tightly connected to the points of the ends of the plates so as to form separate conduits for supplying or outlet of gases flowing at counter-current in alternating spaces formed by the plates, characterized in that it comprises one or more stack (s) of plates (120, 121) obtained by cutting out each pattern or a set of patterns inscribed in a rectangle of a sheet (101) according to claim 3, these plates being arranged alternately in one direction and in the opposite direction obtained after rotation of 180 ° around an axis perpendicular to the plane of the plate (s) (120, 121).

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