FR3057346B1 - EXCHANGE BODY FOR COOLING TOWER - Google Patents

Abstract

The exchange body comprises a plurality of perforated corrugated sheets (10, 10A, 10B) attached to each other each having one or more perforated areas (100) each extending over a plurality of successive corrugations (20) with perforations (30). partially extending into an intermediate zone (23) and respectively into the apex (22) or the hollow (21), the perforations (30) being made on the corrugated sheet, so that the perforated corrugated sheets (10, 10A , 10B) do not have cracks of more than 1mm in length.

Description

Exchange body for cooling tower

The present invention relates to an exchange body for a cooling tower with direct contact between a hot aqueous liquid to be cooled and air.

Such cooling towers are known, for example from the following documents: US3272484, US6877205; US4130613, etc. These towers comprise an exchange or packing body to ensure a heat exchange by direct contact liquid water to cool - air. This exchange can be done against the current, the water flowing through the exchange body down, while the air moves upwards, for example through a fan sucking the air in the tower The exchange could also have been of the current-cross type, the water flowing through the exchange body down, while the air moves from right to left.

To ensure a better contact liquid water - air, it has been planned to use exchange bodies defining series of channels. On some models of exchange bodies, the walls of the channels having openings to allow the liquid flowing in one channel to pass into another adjacent channel.

For the realization of these openings or windows in the wall, the sheets constituting the exchange body are perforated flat, before then being deformed to form channels. During the deformation of such perforated flat sheets, cracks or crack initiators appear, in particular in the folding zones in the vicinity of the openings, all the more so as the perforations have straight edges with angles. When using the exchange bodies, vibrations are generated by the passage of air, these vibrations causing that the cracks can propagate and can generate noise. The thermoplastic sheets constituting the known exchange body advantageously has a thickness of more than 3 mm.

The present invention relates to an exchange body for cooling tower which avoids at least such problems. The subject of the invention is therefore an exchange body for cooling tower with direct aqueous liquid contact to be cooled (the aqueous liquid to be cooled advantageously has a temperature of less than 60 ° C., in particular less than 50 ° C. the temperature of the aqueous liquid to be cooled depends on the possible prior stages of energy recovery) - air (the liquid-air contact in the exchange body operates substantially at atmospheric pressure), said exchange body comprising a series of corrugated sheets (by corrugated is also meant notched) perforated attached to each other (for example each corrugated sheet is attached to adjacent corrugated sheets) by fastening means (for example by points or lines of welding, by dots or lines of glues , by separate fixing areas, etc.), said sheets having a thickness of between 0.2 and 1.5 mm (between two values, the thicknesses of 0.2 to 1.5 mm), advantageously less than or equal to 1 mm (this small thickness allows the exchange body to have a low weight per unit volume and to allow a good heat exchange through the wall), being made of heat-deformable plastic material, in particular thermoplastic, resistant to the aqueous liquid to be cooled (resistant to the aqueous liquid to be cooled means that the plastic material has a dimensional stability in contact with the aqueous liquid to be cooled, and therefore at the temperature of said liquid to be cooled, in general an aqueous liquid or water having a maximum temperature of 60 ° C), said corrugations of the sheets defined hollows possibly at least partially flat (an end portion being advantageously flat to serve as a surface or area of support or contact with another corrugated sheet), vertices possibly at least partially planar (where the vertices are a advantageously flattened or advantageously having a flat end portion to serve as a zone or bearing surface for another corrugated sheet), and intermediate zones with advantageously at least a substantially flat or flat portion extending between each depression and a vertex adjacent to hollow considered.

The perforated corrugated sheets attached to each other form a series of channels for the passage of the aqueous liquid to be cooled and for the passage of air through the exchange body.

The exchange body according to the invention is essentially characterized in that the perforated corrugated sheets of the exchange body each have: (a) one or more perforated zones each extending over several successive corrugations with: (a1) first perforations each extending only partially in the apex of one of the successive corrugations of one or more perforated zones, and partially in one or the adjacent intermediate zones of the vertex considered, preferably in only one of the adjacent intermediate zones of the vertex considered, (a2) second perforations each extending only partially in the recess of one of the successive corrugations of one or more perforated zones, and partially in one or the adjacent intermediate zones of the recess in question, preferably in only one of the intermediate zones; , and preferably, but preferably, (a3) perforations extending only in intermediate zones, and advantageously (b) non-perforated zones extending over a plurality of corrugations between two perforated zones or non-perforated zones between which a perforated zone extends, in which, for each perforated corrugated sheet, the perforations have an equivalent diameter of between 5mm and 30mm, preferably between 6mm and 20mm, for example 6mm, 8mm and 10mm, and are made on the corrugated sheet, so that the perforated corrugated sheets do not have cracks of more than 1mm in length, in particular more than 500pm, more specifically more than 200pm in the perforated zone or zones.

Such cracks or micro-cracks in sheets of small thickness, or even of very small thickness, are more important tearing initiators, which is then a cause of malfunctioning of the exchange body, thus necessitating the stopping of the cooling tower. to replace the defective exchange body or bodies.

The weight per unit volume of an exchange body according to the invention is limited or very limited. This low weight per unit volume allows the exchange body has a low thermal inertia. The weight per unit volume is reduced, on the one hand, by the very small thickness of the sheets, and on the other hand by the number and size of the perforations.

The perforations will preferably be distributed homogeneously or substantially homogeneously. Those skilled in the art can without problem determine the optimum thickness of the sheets, the optimum height of the intermediate zones, the optimum number and the optimum size of the perforations, to obtain a desired weight per unit of volume, but preferably as low as possible. .

By equivalent diameter of an opening is meant the diameter determined by dividing the quadruple of the area of the opening by the perimeter of the opening. For a circular opening, the equivalent diameter corresponds to the diameter. Although the perforations advantageously have a substantially circular or oval section, the shape of the perforations or perforations may be different, for example polygonal, square, rectangular, star, etc., or a shape combining a polygonal section with a curved section.

The exchange body according to the invention advantageously has one or more of the following characteristics, advantageously a plurality of following characteristics: i) the perforations of each perforated sheet are all produced by means of punches, advantageously of circular or oval or square section or rectangular or a combination of these sections (other shapes are possible, but are considered less preferred), moving in the same direction. The perforations could have had sections of other shapes, such as substantially polygonal, square, triangular, rectangular, star-shaped possibly in combination, or even in combination with oval and circular parts. ii) for each perforated corrugated sheet, the recesses each have a substantially flat bottom extending in the same first plane, while the apices each have a flat or flat end portion extending in the same second plane parallel to said first plane, while the perforations of each perforated sheet are all made by means of punches, preferably of circular or oval or square or rectangular section, moving in the same direction perpendicular to said first and second planes. iii) the intermediate zones of the corrugations have a flat portion of width 1 cm or more than 1 cm (preferably 1.5 cm to 5 cm). The flat portion of each intermediate zone advantageously extends in a plane forming an angle advantageously from 20 to 70 ° to said first or second plane A, B, said flat portion of the intermediate zone preferably forming a continuous strip. extending between said first and second planes A, B. The distance separating the planes A and B is advantageously greater than or equal to 8 mm, for example from 12 mm to 40 mm. iv) the perforations, reported in the first plane in a direction perpendicular thereto, all have a section of equivalent diameter equal to or greater than 10 mm, in particular from 10 to 30 mm. The distance separating from one another the perforations of a perforated zone reported in said first plane, measured distance in said first plane where the perforations have been reported, is advantageously equal to or greater than the average of the equivalent diameters of the sections of the perforations reported in the first plane in a direction perpendicular to said first plane, therefore equal to or greater than 10mm, such as 15 to 40mm. v) for each perforated corrugated sheet, the recesses each have a substantially flat bottom extending in the same first plane; vi) the perforations of each perforated zone, reported in the first plane in a direction perpendicular to it, are homogeneously distributed for the zone considered. vii) the corrugated sheets have on their entire surface identical or substantially identical corrugations. viii) As an exemplary embodiment, the intermediate zones of the corrugations have a flat portion 0.8 to 1.5 cm wide, preferably about 1 cm wide for contact between the sheets. The pitch of the undulations is advantageously from 3 cm to 20 cm, whereas the height of the undulation or the height of difference (between the hollow 22 or the plane B and the top 21 or the plane A) is advantageously between 1 cm and 10 cm, advantageously between 2 cm and 6 cm. The intermediate zones form points or zones of support between two adjacent sheets. ix) according to a preferred embodiment, the perforations at each sheet are all oval or circular or square or rectangular or a combination of oval or circular or square or rectangular shape. x) the perforated zones extend over three or more successive undulations, advantageously over 4 to 6 successive corrugations, while the non-perforated zones extend over three or less than three successive corrugations, in particular over two successive corrugations. xi) the perforations at each sheet have a reinforced edge. xii) a combination of such features.

The exchange body according to the invention advantageously has several of the characteristics listed above. The invention also relates to a cooling tower of an aqueous liquid to be cooled by direct contact of the aqueous liquid to be cooled with atmospheric air, said cooling tower comprising exchange bodies according to the invention (main body). exchange as described hereinbefore and advantageously having one or more of the features described above). The direct contact of the aqueous liquid to be cooled with atmospheric air is carried out essentially in the exchange bodies of the cooling tower. The cooling tower may be of the natural draft type, induced draft (for example by a fan sucking the air present in the tower out of it), forced draft (a fan pushing air into the tower ), or of a mixed type. The invention also relates to the use of a cooling tower according to the invention for cooling an aqueous liquid to be cooled by direct contact of the aqueous liquid to be cooled with atmospheric air. The invention also relates to a method for producing an exchange body according to the invention. The process according to the invention is a process for producing an exchange body from sheets of thermo-deformable plastics material able to withstand contact with the hot aqueous liquid to be cooled, advantageously thermoplastic (with a chosen melting or softening temperature). depending on the temperature of the liquid to be cooled, for example, if the liquid to be cooled has a temperature of 50 or 60 ° C., the material will advantageously be chosen to have a softening point greater than 65 ° C.) or more preferably to from a thermoplastic film able to be deformed and cut. The method according to the invention comprises at least the following steps: unwinding of a thermo-deformable film capable of withstanding contact with the hot aqueous liquid to be cooled (by resisting contact with the hot aqueous liquid to be cooled, is meant a film which is chemically and physically stable in contact with the hot aqueous liquid), in particular a thermoplastic film, having a thickness of from 0.2 mm to 1.5 mm, advantageously from 0.2 mm to 1 mm, preferably from 0.2 to 0. , 8mm, said uncoiled film having a first face (advantageously lower) and a second face (advantageously greater) opposite to the first face; at least a thermal treatment of said heat-deformable plastic film, in particular thermoplastic film, to form a corrugated film having a series of corrugations, said corrugations of the sheets defining optionally at least partially flat recesses (for example having a flat end portion or a flat bottom ), possibly at least partially planar vertices (preferably having a flat end portion), and intermediate zones with advantageously at least a substantially flat or flat portion extending between each depression and a vertex adjacent to the trough (For this step the temperature of the film, in the zones to be deformed, is advantageously brought to a temperature close to the melting or softening temperature of the film, but is preferably lower than the melting temperature.), - intermittent longitudinal displacement of the corrugated film with periods of no longitudinal displacement between periods of longitudinal displacements to a perforation unit comprising: (*) a first movable matrix capable of moving between a remote position and a close position in which the first matrix is adapted to fit a portion of the first face of the corrugated film, said first die having a series of passages each adapted for passage of the punch end; (*) a movable counter-matrix able to move between a remote position and a close position in which the counter-matrix is adapted to fit a part of the second face of the corrugated film, said counter-matrix having a series of passages each adapted for the moving punches out of the counter-matrix towards the first matrix, the counter-matrix being arranged with respect to the first matrix so that in a position close to the first matrix and against the matrix a portion of the corrugated film is sandwiched between the die and the counter-die, and (*) a series of movable punches between a retracted position relative to the countermatrix and an extended position in which the punches have their ends extending out of the counter-matrix so as to be able to extend in passages of the first matrix when the matrix and counter matrix are close to each other. For this longitudinal movement, it is advantageous to use a toothed belt system with protuberances adapted to be housed in corrugations of a portion of the corrugated film. Such a system is advantageously used to push the corrugated film toward the punch unit, but also to move or remove the portion of the corrugated film when punched out of the punch unit. (It is clear that the first die and the counter die can each be associated with movable punches to each extend in a passage of the first die or against the die in the retracted position and both in a passage of the first matrix and a passage of the counter matrix in perforation position of the corrugated film), - during periods of non displacement of the corrugated film with adequate positioning of the corrugations relative to the first matrix and the counter matrix, the corrugated film is subjected to a perforation cycle comprising the following sub-steps: (i) the first matrix and the counter-matrix with the punches in the retracted position are moved towards each other to enclose between them a portion of the corrugated film comprising at least three successive corrugations, (ii) the punches are moved to their extended position so that they perforate the portion of the corrugated film contained and each have a end extending into one of the passages of the die, (iii) the punches are again moved to their retracted position to no longer extend through the portion of the waved corrugated film, (iv) the die and counter die are spaced from each other in a position permitting longitudinal displacement of the corrugated film, to put another portion of the corrugated film between the matrix and against the matrix for a new perforation cycle; the perforated corrugated film is moved to a cutting unit to form a series of separate perforated corrugated sheets; - Stacking of separate perforated corrugated sheets, with holding in position the corrugated sheets perforated with each other, to form an exchange body according to the invention.

The method according to the invention advantageously comprises one or more of the following characteristics: i) the perforations of the corrugated film sandwiched are all produced by means of punches, advantageously of circular or oval or square or rectangular section, moving in the same direction. The punches are advantageously hollow and have a cutting edge, preferably beveled. ii) for the corrugated film, the recesses each have an at least partially flat bottom (for example a bottom having a planar end portion) extending in the same first plane B10, while the peaks have a flat or flat end portion extending in the same second plane A10 parallel to said first plane B10, while the perforations of the corrugated film are all produced by means of punches, advantageously of circular or oval or square or rectangular section, moving in the same direction perpendicular to said first and second shots. iii) the perforations, reported in the first plane in a direction perpendicular thereto, advantageously all have a substantially circular or oval section, preferably of the same equivalent diameter. iv) the perforations of each perforated zone, reported in the first plane in a direction perpendicular to it, are advantageously homogeneously distributed for the zone considered. v) the intermittent displacement of the corrugated film is adapted to allow the formation of perforated zones extend over at least three successive corrugations, advantageously over 4 to 6 successive corrugations, while the non-perforated zones extend over three or less than three successive waves, especially on two successive waves. vi) the zone to be perforated is preheated to a temperature below the melting temperature, for example at a temperature close to the softening temperature, before the movement of the punches. vii) the punches are heated to a temperature close to the softening temperature of the film to be perforated.

Points vi) and vii) of the method are advantageous to ensure that the edges of the perforations are properly cut in a sheet of very small thickness, and / or to ensure that the edges of the perforations are reinforced.

Features and details of the invention will become apparent from the following statement, in which reference is made to the accompanying drawings.

In these drawings, FIG. 1 is a partial schematic perspective view of an exchange body; - Figure 2 is a plan view of a corrugated sheet and perforated; FIG. 3 is a sectional view of a corrugated and perforated sheet attached by soldering points to another corrugated and perforated sheet; and FIG. 4 is a schematic view of an installation for producing an exchange body according to the invention.

Figure 1 is a schematic view of a portion of an exchange body according to the invention.

This exchange body is intended for a cooling tower to ensure direct liquid aqueous contact to cool - air. This exchange body comprises a series of C channels (advantageously parallel), for example extending in a vertical direction, or extending in a horizontal direction. The liquid to be cooled, for example water from a circuit of an industrial process having a temperature of 50 to 55 ° C, flows down the channels, while the cooling air moves to countercurrent (bottom to top).

This exchange body 1 comprises a series of partially perforated corrugated sheets 10, 10A, 10B, etc. fastened together by fastening means, for example points or weld lines 11 (for example by simple heat sealing or thermal welding of the sheets together or by adding points or weld lines. points or lines of glue, for example capable of being heat-cured and / or UV radiation) to define for example hexagonal section channels. The sheets 10, 10A, 10B, ... have a thickness of less than 1mm (for example from 0.4mm to 0.8mm) and are made of thermoplastic material, for example PVC or polypropylene. The sheets could also have been of the multilayer type with or without a frame. The material is chosen to withstand hot water with a temperature above 60 ° C. Advantageously, the chosen material will be of the hot-melt type, to allow the realization of weld points or lines by simple heat treatment localized at a temperature near or above the melting temperature. The sheets 10, 10A, 10B could also have been glued to each other.

The sheets 10, 10A, 10B have a series of identical corrugations 20, each corrugation defining a substantially flat depression (or bottom) 21, a substantially flat top 22, and substantially planar intermediate zones 23 extending between the recess 21 and the adjacent vertices 22 to the hollow considered. Two sheets are attached to each other so that the vertices 22 of a sheet 10A touch the recesses 21 of an adjacent sheet 10B. The vertices 22 of a sheet 10 or 10A or 10B extend in the same plane A10, A10A, A10B, while the recesses 21 of the sheet considered extend in the same plane B10, B10A, B10B, parallel to the plane A10, A10A, A10B (the planes A10, A10A, A10B, B10, B10A and B10B are parallel to each other). The intermediate zones 23 extend in planes D1, D2 inclined with respect to the planes A10 and B10. The angle of inclination of the planes D1, D2 is for example 60 ° with respect to the plane A or B.

The perforated corrugated sheets 10, 10A, 10B of the exchange body each have: (a) perforated areas 100 extending over a plurality of corrugations with (a1) perforations 30 extending only partially into the apex 22 of a plurality of successive corrugations and partially in one or the adjacent intermediate zones 23 of the considered vertex 22, (a2) with perforations 30 extending only partially in the recess 21 of several successive corrugations and partially in one or the intermediate intermediate zones 23 of the recess in question 21, and optionally (a3) perforations 40 extending only in the intermediate zones, and (b) non-perforated zones 101 extending over a plurality of corrugations 20 between two perforated zones 100 or located along two opposite edges of a zone perforated 100.

For each of the perforated corrugated sheets 10, 10A, 10B, the perforations 30 of equivalent diameter of at least 6 mm, preferably 6 to 15 mm, are made on the corrugated sheet, so that the perforated corrugated sheets do not have no cracks of more than 1mm in length, especially more than 500pm, more specifically more than 500pm in the perforated areas. The absence of cracks or crack initiation makes it possible to ensure a better longevity of the product and to avoid the appearance of large cracks in the exchange body, which are then sources of noise nuisances, or even obstructions or clogging of one or more channels C.

In addition, the absence of cracks and micro cracks makes it possible to ensure more constant exchange properties over time throughout the exchange body.

In the embodiment shown, the perforations 30 of each perforated corrugated sheet are all made by means of punches of circular section moving in the same direction.

As can be seen in Figure 2, the perforations 30, reported in the first plane (for example in the plane B10 or A10) in a direction perpendicular thereto, all have a circular section, preferably of the same diameter. Reported in said plane A, the openings are distributed homogeneously in the perforated zone.

The corrugated sheets have on their entire surface identical and uniformly spaced corrugations. This allows by the use of a toothed belt (with notches adapted to be housed in several successive corrugations of the sheet) to ensure a movement of the sheet or corrugated film.

The hollow 22 and the top 21 have a width of the order of 1 to 3 cm, while the flat portion of the intermediate zone 23 has a width of 1 to 3 cm. The distance separating the planes A10 and B10 is for example of the order of 1 to 2.5 cm.

Using circular punches, the perforations extending partially into a recess 22 or apex 21 and an intermediate zone 23 have a shape combining a circular portion at the recess 22 or apex 21 and an oval portion in the intermediate zone 23.

The perforated zones 100 extend over more than three successive corrugations, advantageously over 4 to 6 successive corrugations, or even more, while the non-perforated zones 101 extend over three or less than three successive corrugations, in particular over two successive corrugations. .

Figure 4 is a schematic view of an installation for producing an exchange body according to the invention. This installation comprises: a stripping installation 50 of a thermoplastic film (PVC or polypropylene) with a thickness of, for example, 0.5 to 0.8 mm; an embossing unit 51 for forming a series of corrugations 30 in the thermoplastic film, a perforation unit 52 with a displacement control system 52A of the corrugated film to a "matrix, counter-matrix and punch" assembly, and a 52B displacement control system of perforated corrugated film out of the "die, counter die and punch" assembly; a cutting unit 53 of the corrugated film perforated as a separate separate sheet; a unit for assembling and welding the sheets together to form a multi-sheet exchange body.

When assembling the sheets, the sheets are advantageously placed relative to one another so that the perforated corrugated areas of a sheet are superimposed on the perforated areas of an adjacent sheet. Advantageously, the perforations 30 of a recess 22 of a corrugation 20 of a sheet are placed facing the perforations 30 of an apex 21 of another sheet.

By using such an installation, it is possible to produce an exchange body according to the invention (in particular of the type described above) in the following manner: - unwinding of a thermoplastic film (PVC, polypropylene) of thickness less than 1.5 mm, advantageously less than 1 mm, for example from 0.2 mm to 0.8, in particular from 0.5 mm to 0.8 mm, said uncoiled film having a first face (advantageously lower) and a second face ( advantageously greater) opposite to the first face; at least a thermal treatment of said thermoplastic film to form a corrugated film having a series of corrugations 20, said corrugations of the sheets defining recesses 22 at least partially flat, vertices 21 at least partly flat, and intermediate zones 23 with advantageously at at least one substantially flat portion extending between the recesses 21 and the vertices 22, intermittent longitudinal displacement of the corrugated film with periods of longitudinal non-displacement between periods of longitudinal displacements to a perforation unit comprising (*) a first moving matrix able to move between a distant position and a close position in which the first die is adapted to fit a portion of the first face of the corrugated film, said first die having a series of passages each adapted for the passage of the end of punches ; (*) a movable counter-matrix able to move between a remote position and a close position in which the counter-matrix is adapted to fit a part of the second face of the corrugated film, said counter-matrix having a series of passages each adapted for the moving punches out of the counter-matrix towards the first matrix, the counter-matrix being arranged with respect to the first matrix so that in a position close to the first matrix and against the matrix a portion of the corrugated film is sandwiched between the die and the counter-die, and (*) a series of movable punches between a retracted position relative to the countermatrix and an extended position in which the punches have their ends extending out of the counter-matrix so as to be able to extend in the passages of the first matrix when the matrix and against matrix are close to each other; during periods of non-displacement of the corrugated film with adequate positioning of the corrugations with respect to the first matrix and the counter matrix, the corrugated film is subjected to a perforation cycle comprising the following sub-steps: (i) the first matrix and the against die with the punches in the retracted position are moved towards each other to enclose between them a portion of the corrugated sheet having at least three successive corrugations, (ii) the punches are moved to their extended position so that they perforate the enclosed corrugated sheet portion and have their ends extending into the die passages, (iii) the punches are again moved to their retracted position to no longer extend through the enclosed corrugated sheet, (iv) ) the matrix and the counter-matrix are spaced from each other in a position permitting a longitudinal displacement of the corrugated film, p to put another part of the corrugated film between the matrix and counter matrix for a new perforation cycle; the perforated corrugated film is moved to a cutting unit to form a series of perforated corrugated sheets; - Stacking sheets corrugated and perforated, holding the sheets in position relative to each other (for example by gluing or welding), to form an exchange body according to the invention.

The movement of the punches through the corrugated film (thermoformed), either for the perforation or for the removal of the punches out of the corrugated film, is advantageously operated with the matrix and the counter-matrix in position enclosing the part of the film where the punches must act or have acted.

The perforations of the corrugated film sandwiched are all made by means of punches of circular or oval or square or rectangular section moving in the same direction.

The perforations, reported in the first plane in a direction perpendicular to it, all have a circular or oval or partially circular or oval section, preferably of the same diameter (measured in said plane).

The weight per unit volume of embodiments of an exchange body according to the invention is, for example, less than 100 kg / m 3, advantageously less than 50 kg / m 3, preferably less than 40 kg / m 3, in particular for example less than 30kg / m3.

In the process according to the invention, the steps are advantageously used: *) the zone to be perforated is preheated to a temperature below the melting point, for example at a temperature close to the softening temperature, before the punches are moved. And / or **) the punches are heated to a temperature close to the softening temperature of the film to be perforated.

The aforementioned points *) and / or **) of the method are advantageous to ensure that the edges of the perforations are properly cut in a sheet of very small thickness, and / or to provide some reinforcement of the perforations along their length. edge, this slight strengthening also reinforcing the stability of the corrugated sheets and thus the body of exchange.

Claims (15)

1. Exchange body for cooling tower with aqueous liquid direct contact to be cooled - air, said exchange body comprising a series of perforated corrugated sheets (10, 10A, 10B) fastened together by fixing means, said sheets of thickness from 0.2mm to 1.5mm being made of thermally deformable plastics material, in particular thermoplastic, resistant to the aqueous liquid to be cooled, said corrugations (20) of the sheets defining recesses (21), vertices (22), and intermediate zones (23) extending between each hollow (21) and an adjacent vertex (22) of the hollow in question, characterized in that the perforated corrugated sheets (10, 10A, 10B) of the exchange body each have: a) one or more perforated zones (100) each extending over a plurality of successive corrugations (20) with: (a1) first perforations (30) each extending only partially in the apex (22) of one of the successive corrugationsone or more perforated zones, and partially in one or the intermediate zones (23) adjacent to the considered vertex (22), (a2) of the second perforations (30) each extending only partially in the depression (21) of one of the successive corrugations (20) of one or more perforated zones, and partially in one or the adjacent intermediate zones (23) of the hollow in question (21), and in which for each of the perforated corrugated sheets (10, 10A, 10B) , the perforations (30) have an equivalent diameter of between 5 mm and 30 mm, and are made on the corrugated sheet, so that the perforated corrugated sheets (10, 10A, 10B) do not have cracks of more than 200pm in the perforated zone or zones. 2. Exchange body according to the preceding claim, characterized in that the perforations (30) of each perforated sheet (10, 10A, 10B) are all made by means of punches moving in the same direction. 3. Exchange body according to claim 1 or 2, characterized in that for each perforated corrugated sheet (10, 10A, 10B), the recesses (21) each have a substantially flat bottom extending in the same first plane ( B10), while the vertices (22) each have a planar or flat end portion extending in the same second plane (A10) parallel to said first plane (B10), and in that the perforations (30) of each perforated sheet (10, 10A, 10B) are all made by means of punches moving in the same direction perpendicular to said first and second planes (A10.B10). 4. Exchange body according to any one of the preceding claims, characterized in that the intermediate zones (23) of the corrugations (30) have a flat portion of width 1cm or more than 1cm. 5. Exchange body according to claim 3, characterized in that the perforations (30), reported in the first plane (B10) in a direction perpendicular thereto, all have a cross section of equivalent diameter equal to or greater than 10mm . 6. Exchange body according to any one of the preceding claims, characterized in that for each perforated corrugated sheet (10, 10A, 10B), the recesses (21) each have a substantially flat bottom extending in the same first plane (B10), and in that the perforations (30) of each perforated zone (100), reported in the first plane (B10) in a direction perpendicular thereto (B10), are distributed homogeneously for the zone considered. 7. Exchange body according to any one of the preceding claims, characterized in that the corrugated sheets (10, 10A, 10B) have over their entire surface substantially identical corrugations (20). 8. Exchange body according to any one of the preceding claims, characterized in that the perforated zones (100) extend over three or more successive undulations while the non-perforated zones (101) extend over three or less than three successive waves. 9. Exchange body according to any one of the preceding claims, characterized in that the perforations at each sheet have a reinforced edge. 10. Cooling tower of an aqueous liquid to be cooled by direct contact of the aqueous liquid to be cooled with atmospheric air, said cooling tower comprising exchange bodies according to any one of claims 1 to 9. 11. Use of a cooling tower according to claim 10 for cooling an aqueous liquid to be cooled by direct contact of the aqueous liquid to be cooled with atmospheric air. 12. A method of producing an exchange body according to any one of claims 1 to 9 from thermoformable plastic sheets capable of withstanding contact with the hot aqueous liquid to be cooled, said method comprising at least the following steps : unwinding a heat-deformable film capable of withstanding contact with the hot aqueous liquid to be cooled, 0.2 mm to 1.5 mm thick, said uncoiled film having a first face and a second face opposite to the first face; at least a thermal treatment of said heat-deformable plastic film, to form a corrugated film having a series of corrugations (20), said corrugations (20) of the sheets defining recesses (21), vertices (22, and intermediate zones (23); ) extending between each recess (21) and an apex (22) adjacent to the recess in question, - intermittent longitudinal displacement of the corrugated film with periods of longitudinal non-displacement between periods of longitudinal displacements to a perforation unit comprising: (* ) a first movable matrix capable of moving between a remote position and a close position in which the first matrix is adapted to fit a portion of the first face of the corrugated film, said first matrix having a series of passages each adapted for the passage of the end of punches; (*) a movable counter-matrix able to move between a remote position and a close position wherein the counter-matrix is adapted to fit a portion of the second face of the corrugated film, said counter-matrix having a series of passages each adapted for the movement of punches out of the counter-matrix to the first matrix, the counter matrix being arranged with respect to the first matrix so that in a position close to the first matrix and the counter matrix a portion of the corrugated film is sandwiched between the matrix and the counter matrix, and (*) a series of movable punches between a position retracted relative to the counter-matrix and an extended position in which the punches have their ends extending out of the counter-matrix so as to be able to extend into passages of the first matrix when the matrix and the counter matrix are brought closer together. the other ; during periods of non-displacement of the corrugated film with adequate positioning of the corrugations with respect to the first matrix and the counter matrix, the corrugated film is subjected to a perforation cycle comprising the following sub-steps: (i) the first matrix and the against matrix with the punches in the retracted position are moved towards each other to enclose between them a portion of the corrugated film having at least three successive corrugations, (ii) the punches are moved to their extended position so that they perforate the portion of the corrugated film sandwiched and each having an end extending in one of the passages of the matrix, (iii) the punches are again moved to their retracted position to no longer extend through the portion of the corrugated film sandwiched (iv) the matrix and counter matrix are spaced from each other in a position permitting longitudinal displacement of the corrugated film to put another part of the corrugated film between the matrix and against the matrix for a new cycle of perforation; the perforated corrugated film is moved to a cutting unit to form a series of separate perforated corrugated sheets (10, 10A, 10B); - Stacking distinct perforated corrugated sheets (10, 10A, 10B), with holding in position the corrugated sheets perforated therebetween, to form an exchange body according to any one of claims 1 to 9. 13. Method according to the preceding claim, characterized in that the perforations of the corrugated film clamped are all made by means of punches, moving in the same direction. 14. The method of claim 12 or 13, characterized in that for the corrugated film, the recesses each have a bottom at least partially flat (21) extending in the same first plane (B10), while the vertices (22). ) have a flat end part extending in the same second plane (A10) parallel to said first plane (B10), in that the perforations (30) of the corrugated film are all made by means of punches, moving in the same direction perpendicular to said first and second planes (A10, B10). 15. A method according to claim 14, characterized in that the perforations (30), reported in the first plane (B10) in a direction perpendicular thereto, all have a substantially circular or oval or square or rectangular section.