ES2312143T3 - COLLECTION BOX WITH LID FOR HIGH PRESSURE FLUIDS, HEAT EXCHANGER INVOLVING SUCH BOX AND METHOD FOR MANUFACTURING. - Google Patents

Abstract

The box has a collector plate (26) comprising openings (28) for inserting heat exchange tubes (18). A cover (44) is formed by machining a metal bar and comprises an internal surface (72) and external surface. Distribution channels (70) e.g. groove, are formed in the metal bar by emerging on the internal surface while permitting material of the bar to close a volume of the cover at the level of longitudinal ends of the cover, where the channels communicate with the heat exchange tubes. An independent claim is also included for a method for fabricating a collector box.

Description

Collector box with lid for high fluids pressure, heat exchanger involving such box and method for its manufacture

The invention relates to the field of heat exchangers and especially to exchangers intended to be traveled by a high pressure fluid.

To this effect, the invention relates more specifically to the air conditioning evaporators susceptible to be traversed by a gaseous refrigerant fluid, such as natural gases such as carbon dioxide or CO2. This type of exchangers are particularly applied in vehicles cars

It will be remembered that, in a circuit of air conditioning traveled by a refrigerant fluid of this type, this fluid essentially remains in a gaseous state and at a very high pressure between 100 and 150 baros. By consequently this type of heat exchangers, and especially their collector boxes must be able to withstand these pressures high, generally the value being burst pressure recommended three times that of the nominal pressure value of functioning.

Collector boxes are already known, obtained by welding, which are designed to resist these pressures high.

Thus, document FR 2 793 016 discloses a box collector formed by a multiplicity of stacked plates that they involve fluid passage grooves. The distribution is assured for these flat plates and the collector box has a lid It also consists of a multiplicity of stacked plates. All These plates are assembled together by welding.

JP 2002-1588722 discloses a collection box with a closed extruded tank by flat end plates. The tube stop is secured either by an intermediate flat plate, arranged between the tubes and the deposit, either by a specific profile of the section of the Deposit.

Other collector boxes of this type too are disclosed by documents JP 2002-43332, WO / 03 102 486 and EP 0 563 471.

Document FR 2 793 015 discloses a box collector according to the preamble of claim 1.

All these known collector boxes, or are difficult to weld, or require a considerable number of manufacturing operations that do their manufacturing procedure complex and expensive to perform.

The invention is especially intended solve the aforementioned inconveniences.

The invention proposes for this purpose a box heat exchanger manifold, comprising a plate collector provided with openings for the insertion of tubes heat exchange, and a lid that delimits channels of distribution that communicate with the tubes.

According to the invention, the lid is a bar metallic that has an inner face and an outer face opposite, while the distribution channels are throats made in the thickness of metal bar material, flowing into the inner face, leaving material of way to close the volume of the lid at the level of its ends Longitudinal

In this way, the cover is made by machining of a thick metal bar, which simplifies its manufacturing and allows to realize an element that can resist high pressures

Steps of advantageously are provided communication between the cover and the collector plate.

In a first embodiment of the invention, the communication steps are delimited by a distribution plate interposed between the collector plate and the face inside of the lid.

In a second embodiment of the invention, the communication steps are bar throats metal that on the one hand flow into the distribution channels and on the other hand on the inside face of the lid. This form of realization allows in this way to economize the plate distribution of the previous embodiment, whereby delete a component

According to an advantageous feature of the invention, distribution channels and communication steps They are mechanized.

Due to the fact that the throats that form the channels are not draining, avoiding having to resort to end plates and thus reduce the number of pieces.

According to another feature of the invention, the Cap is obtained from an extruded metal bar.

In an advantageous embodiment, the outer face of the extruded metal bar is shaped so that present a profile that involves a plurality of domes, or arcs, in correspondence with the channels. The distribution channels can have a constant interior section throughout its length, or even a variable inner section throughout its length.

The lid can have a single series of channels each of which extends along the bar metallic Specifically, it is the case of a lid that forms a return, located on the opposite side of a cover that contains provisions for the entry and exit of the fluid.

The lid can also have at least two series of channels each of which extends to a part of The length of the metal bar. This is especially the case with a lid that includes, as mentioned above, provisions for the entry and exit of the fluid.

In the invention, the channels have advantageously a bottom with a transverse U-profile, which allows to improve the resistance to the pressure of the fluid.

The channels advantageously have about one end face of the metal bar, a curved longitudinal profile delimited by a radius.

According to another aspect, the invention relates to a heat exchanger that involves a bundle of tubes and at least a collecting box as described above. This heat exchanger is advantageously made in the form of an evaporator

A particular embodiment proposes that the heat exchanger behaves at least two steps and that the interior sections of the distribution channels allow control and balance the flow of the fluid in the steps.

Still under another aspect, the invention relates to a manufacturing process for a collecting box for heat exchanger, as defined above, that It includes the following operations:

to)

make a collector plate that It involves openings to accommodate tubes;

b)

make means of distribution that they involve communication steps;

C)

make a lid from a bar metallic that has an inner face and an opposite outer face,  machining distribution channels in the form of throats obtained by machining the metal bar according to the longitudinal direction of this which flow into said inner face; Y

d)

assemble the cover on the collector plate with interposition of the means of distribution so that communication steps lead on the one hand to the channels of distribution and on the other hand in the plate openings collector

In a first embodiment, the operation b) comprises the preparation of a distribution plate which delimits the communication steps, while operation d) comprises the interposition of the distribution plate between the collector plate and the inside face of the lid.

In a second embodiment, the operation b) includes the completion of the communication steps in the form of throats made by mechanization according to the direction cross section of the metal bar, which on the one hand flows into the distribution channels and on the other hand on the inside of the cover, while operation b) comprises the assembly direct from the collector plate against the inside of the top.

Advantageously, operation c) comprises the preparation of an extruded metal bar and mechanization of channels by means of a suitable multistage rotary tool to mechanize the channels simultaneously in one part so less than the metal bar.

In the following description, made only to example title, reference is made to the attached drawings, in the which:

- Figure 1 is a perspective view of the Exploded view of a heat exchanger, in the example an evaporator for air conditioning circuit, which includes a mounted beam of tubes between two collecting boxes according to the invention;

- Figure 2 is a sectional view partial transverse of one of the collector boxes of the heat exchanger of figure 1;

- Figure 3 is an end view of the lid of the collecting box of figure 2, before machining;

- Figure 4 is a view analogous to the figure 3, after machining the lid channels;

- Figure 5 schematically represents the mechanization by means of a multistage rotary tool;

- Figure 6 is a partial sectional view longitudinal of the lid showing the end of a channel, performed in a non-leading way;

- Figure 7 is a sectional view longitudinal of a cover that includes two series of channels;

- Figure 8 is a sectional view longitudinal of a cover that involves a single series of channels;

- Figure 9 is a variant of Figure 7 in which the section of the channels has an evolutionary form;

- figure 10 is a variant of figure 8 in which the section of the channels has an evolutionary form;

- Figure 11 is a sectional view longitudinal of a cover whose channel has another shape evolutionary;

- figure 12 is a view analogous to figure 11 in another embodiment variant;

- Figure 13 schematically illustrates a circulation distribution for a four-step evaporator that It has two collector boxes according to the invention;

- Figure 14 illustrates the inside face of a cap that includes at the same time longitudinal throats and parallel transverse throats made by mechanization;

- Figure 15 is a sectional view partial transverse of a collecting box comprising a lid according to figure 14; Y

- Figure 16 is another sectional view partial transverse of the collecting box of figure 15.

First, reference is made to the figure 1 showing the exploded view of a heat exchanger 10 which it comprises a beam 12 mounted between an upper collecting box 14 and a lower collecting box 16, the heat exchanger being considered in an upright position.

Beam 12 is composed, in the example, by two rows of tubes 18 (of which only one is visible in the figure 1) and by 20 interleaved corrugated sheets common to the two rows of tubes. The collection box 14 is provided with two tubes of entry / exit 22 and 24 that serve respectively for admission and the evacuation of a fluid that runs through the beam tubes.

In the example, heat exchanger 10 it is made in the form of an evaporator suitable to be run through a supercritical refrigerant fluid, in particular CO2, whose pressure can reach values of the order 100 to 150 baros. This fluid exchanges heat with a flow of air that sweeps the tube bundle to produce an air flow air-conditioned, in particular in a motor vehicle.

It is observed that the collecting box 14 involves a collector plate 26 provided with openings 28 to accommodate tubes of the make. The openings 28 have an elongated shape and are arranged according to two rows in correspondence with the two rows of tubes.

The collector plate 26 has a general shape rectangular and behaves, along its two major sides, crimping elements 30. It involves an extension 32 in which holes 34 and 36 are arranged for the respective assembly of tubes 22 and 24.

Above the collector plate 26, it is located a distribution plate 38 which comprises two rows of steps of communication 40, in the form of slots, each of which communicates with a tube 18 and a row of communication steps 42, in the form of grooves, of greater width each of which communicates with two adjacent pipes that belong to the two rows of the beam. Steps 40 and 42 contribute to fluid distribution and its circulation in the beam tubes according to a defined path, which will be described later with reference to figure 13.

Above the distribution plate 38 is located a cover 44 intended to be held against the plate collector, clamping the distribution plate 38, by action of the crimping elements 30.

The lower collecting box 16 is made of similar way, except that it does not involve prolongation. It consists of a collecting plate 46, a distribution plate 48 and a cover 50. It will be noted that the distribution plate 48 has two rows of steps 52, in the form of slots, each of which communicates with a tube of the beam at its bottom.

Reference is now made to Figure 2 which represents a cross-sectional view of the collecting box 14. The collector plate 26, the distribution plate 38 and cover 44. Collector plate 26 is a embedded plate presenting a flat inner face 54 to accommodate the distribution plate 38 and an outer face 56 from the which extend collars 58 that respectively surround the openings 28 that house the tubes.

In the example shown, the outer face 56 is directed down and the collars 58 are also directed down. These collars are therefore arranged according to two rows in correspondence with two rows of openings 28. In the example, collars and openings have a section general rectangular to allow flat tubes 18 of section homologous exterior.

The crimping elements 30, as already indicated, are formed along the two major sides of the collector plate 26. They are made in the form of a folded edge, in the form of a battlement, which involves a certain number of legs or fingers 60 (see also figure 1).

The distribution plate 38 has a face flat interior 62 suitable to be in contact with the face flat inside 54 of the collector plate and a flat outer face 64 opposite, suitable for housing lid 44.

In the thickness of the distribution plate, they are practiced steps 40 and 42, in the form of grooves, cited. In the Figure 2 shows two steps 40 that communicate respectively with two adjacent tubes that belong respectively to the two rows of beam tubes.

The distribution plate 38 forms the same time limit of introduction for the tubes as it is observed in the Figure 2. Accordingly, the respective ends of the tubes do not may exceed the plane defined by the inner face 54 of the collector plate

The cover 44 is made from a bar thick metal with two parallel edges 66 (figure 2) for the support of crimping elements 30. So when the legs 60 are folded, hold the lid in the direction of the collector plate imprisoning the distribution plate. Cover 44 it implies, as already observed in the section of figure 2, a series of projections 68, six according to the transverse direction. These Highlights 68 respectively delimit channels 70 that communicate with the beam tubes through communication steps 40 and 42 (in slot shape) of the distribution board.

These highlights are conveniently arranged to allow the cooling fluid to penetrate inside the collecting box 14 through the tube 22, then that circulate in the beam tubes between the collection box 14 and the box manifold 16 then exit the heat exchanger through the tube output 24. The manner in which fluid flow is effected in The beam will be described later in detail.

As seen in figures 1 and 2, the cover 44 It has a general rectangular shape, extending each of the protrusions 68 in the longitudinal direction.

The metal bar that forms the lid 44 is a thick bar with an inner face 72, made flat, suitable to be applied against the flat outer face 64 of the plate of distribution 38 (figure 2). It is more specifically a extruded bar whose profile, before machining, is represented in figure 3. It is observed that this bar comprises, on the side opposite the inner face 72, an outer face conformed 74, whose profile defines the six highlights 68, of profile in dome or arch, as well as the two support edges 66. The profile of the bar is also limited by two side faces 76.

According to the invention, channels 70 are obtained by machining from the inner face 72 to obtain the profile shown in figure 4. It is noted that channels 70 are formed by U-profile throats, therefore background rounded in correspondence with the domes or arches mentioned. By consequently the profile obtained after machining (figure 4) define a succession of arcs that have a sufficient thickness to allow good pressure resistance. Taking into account the fact that the mechanization is done in a bar metallic, the thickness of the latter can be controlled so that each time a wall of sufficient thickness is obtained to resist the operating pressures of the collector box and therefore of the heat exchanger.

Figure 5 shows how the mechanization of channels can be realized by means of a rotary tool 78 made in the form of a multistage strawberry being able to revolve around of an axis XX and which involves a succession of crowns 80 in profile rounded, in this case six, to simultaneously perform the six channels 70 in the cover 44. The mechanization is carried out moving the tool in the longitudinal direction of the bar, the axis of rotation of the tool being oriented transversely.

Reference is now made to Figure 6 which shows a channel 70 having an end 82 that ends at a distance A from one end face 84 of the cover 44. This end 82 it presents, near the end face 84, a longitudinal profile curved delimited by a radius R. The latter corresponds advantageously to the radius of the crowns 80 of the tool mechanization 78. Therefore the end of each of the Channels 70 is realized non-draining which allows to avoid the resource has end plates to close the channels. The other End of the channels 70 is performed analogously. Said of otherwise, the throats that form the channels are made in the material thickness of the metal bar, leading to the face interior 72, allowing matter to remain so that it closes the volume of the lid at the level of its longitudinal ends (faces of end 84).

Reference is now made to Figure 7 which shows, in longitudinal section, a cover 44 according to the invention in An embodiment. It is observed that this cover has two series of channels 70A and 70B, presenting channels 70A a length longer than channels 70B and extend from the side of the extension 32 (figure 1). In the example, channels 70A and 70B They have a constant interior section throughout its length.

Figure 8 shows, sectional view longitudinally, the lid 50 of the opposite collection box, which is extends in a length less than the cover 44 and which involves a single series of 70C channels to form return. 70C channels are they extend to the entire length and in this case they also have a constant interior section. As will be seen later, cover 44 of figure 7 and the cover 50 of figure 8 allow defining a four-step circulation evaporator.

Figure 9 illustrates a variant of the cover 44 of Figure 7 in which channels 70B have a section constant interior while 70A channels have a section variable interior, presenting the bottom of the channels a Slope with an angle A1.

Figure 10 illustrates a variant of the lid 50 of Figure 8 and it is seen that channels 70C also have a internal variable section whose bottom has a double slope defined by two opposite A2 angles.

Figure 11 shows another type of profile of Variable inner section for a 70C channel. Each of the 70C channels features a main part 85 made by a first mechanization and a deeper central part 86 made for a second mechanization. This profile requires a first mechanization. This profile requires a first mechanization by a analogous tool to the one described above and a second mechanization to form, in a part of the length of the channel, the deepest central part 86.

Figure 12 illustrates another variant in which the channels 70 have a variable inner section made by a single mechanization, therefore by a single tool. He bottom of each channel has an inclined part 87 defined by a slope of angle A3 and a part 89 of constant depth. It is understood that the machining tool must move from controlled way with respect to the metal bar to control The depth of mechanization.

Resort to channels of variable interior section, therefore of variable depth, it allows each time control the flow of the fluid in the tubes that flow into the channels in question.

Figure 13 shows, schematically, the distribution of a fluid by a four-step exchanger, in this case an evaporator, in which it has been represented schematically covers 44 and 50. The fluid penetrates the box collector associated with lid 44 as shown by arrow F1. It flows into 70.1 channels of diminishing depth.

The fluid then runs a part of the tubes 18 of a first row corresponding to a first step P1 to lead to a series of 70.2 channels of variable profile of the cover 50. These channels 70.2 extend over the entire length of the lid 50 and have a profile analogous to that of Figure 10. The fluid then comes out of channels 70.2 on the other hand of the tubes of the first row to constitute a second step P2 and thus reach channels 70.3 of cover 44 which, in the example, They have a constant section. The fluid passes from these channels 70.3 to other channels 70.4 as shown by arrow F2. These channels  70.4 also have a constant interior section.

The fluid comes out of the box upper collector running a part of the tubes of the second row to constitute a third step P3 and reach channels 70.5 which generally extend to the entire length of the lid 50. These channels 70.5 have a profile analogous to channels 70.2. He fluid then leaves the bottom collecting box to constitute a fourth step P4 that passes through a part of the Second row tubes. The fluid thus reaches channels 70.6 having a variable internal section analogous to that of the channels 70.1. The fluid then leaves the heat exchanger as  It is shown with arrow F3.

Thus, you can work on the distribution of fluid in the channels made inner section channels variable. You can control and balance the fluid flow in the different steps P1 to P4, and this playing with the speed of the fluid thanks to the different interior sections of the channels.

The components of the collection box (collecting plate 26, distribution plate 38 and cover 44) are each made from a metal plate, preferably made of aluminum alloy, thick enough to withstand the considerable pressures of the cooling fluid. The fact of making several projections 68 in the lid allows small volume channels 70 to be formed that delimit the effect of fluid pressure on the components of the collecting plate
Torah.

These components are intended to be assembled. by welding once a provisional assembly has been obtained by crimping. Therefore it is necessary to provide a plating of welding.

The box manufacturing procedure Collector 14 essentially comprises the following operations:

to)

make a collector plate 26 or 46;

b)

make distribution media, here a distribution plate 38 or 48;

C)

make a cover 44 or 50 from a metal bar as defined above; Y

d)

assemble the cover on the collector plate with insertion of the distribution means so that the steps of communication 40 or 42 lead on the one hand in the channels of distribution 38 or 48 and on the other hand in openings 28 of the collector plate 26 or 46.

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In the preceding embodiment, the operation b) includes the preparation of a distribution bale 38 or 48 delimiting communication steps 40 and 42 while operation d) comprises interposing the plate of distribution between the collector plate 26 or 46 and the inner face 72 of the lid.

Next, the cover 14 is set in the collecting plate 26 by means of crimping elements 30, closing the distribution board.

Reference is now made to Figure 14 which shows another embodiment in which the lid 88 resembles to cover 44 described above and includes two series of channels 70A and 70B in the form of parallel longitudinal throats made according to the longitudinal direction of the metal bar. Cover It also includes communication steps 90 and 92 functionally analogous to communication steps 40 and 42 described previously. However, these communication steps 90 and 92 are in this case parallel transverse throats made by machining according to the transverse direction of the metal bar, leading to the distribution channels 70A and 70B and on the other hand on the inner face 94 of the lid (figures 15 and 16). Communication steps 90 and 92 are separated by a step P corresponding to that of the tubes.

Therefore, it is no longer necessary to insert a distribution plate between the lid and the collector plate, what which deletes a component. The assembly operation d) comprises therefore the direct assembly of the collector plate 28 or 46 against the inner face 94 of the lid 88. The lid is therefore set directly on the collector plate.

In the embodiment of figures 14 a 16, the mechanization of the throats of the lid is carried out in two stages:

one)

throats mechanization Longitudinal (channels 70A and 70B),

2)

throats mechanization transversal (steps 90 and 92).

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The cover 88 thus groups the functions of passage and distribution of the fluid. This allows to reduce the number of heat exchanger parts, facilitate the Assembly procedure and decrease the risk of leakage. further the inner face 94 of the lid 88 can be machined forming cavities or steps 96 (figures 15 and 16) that form stops for the introduction of the tubes 18. Once the box has been assembled collector, the heat exchanger assembly may be assembly. The components of beam 12 (tubes and plates interspersed) are arranged against each other and the ends of the tubes are located, on the one hand, in the openings of the box collector 14 and, on the opposite side, in the openings of the box collector 16.

Whatever the embodiment of the collector box, the heat exchanger assembly can welded then, in a single operation, by step by a suitable welding oven. During welding, a plating of welding ensures the union between the different components.

You can, in variant, weld the boxes collectors separately before assembling them to the beam and making a welding of the exchanger assembly.

The collection box 16 is made in a manner analogous to the collection box 14, except that it does not involve extension for the assembly of inlet and outlet pipes of fluid.

The collecting box of the invention is susceptible of numerous embodiments. It mainly applies to heat exchangers traveled by a cooling fluid at high pressure, in particular by a supercritical fluid such as CO_ {2}, of the type of those destined for vehicles cars

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References cited in the description

This list of references cited by the applicant is intended solely to help the reader and not It is part of the European patent document. Although it has been put maximum care in its realization, errors cannot be excluded or omissions and the EPO declines any responsibility in this respect.

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Patent documents cited in the description

FR 2793016 [0005]

JP 20021588722 B [0006]

JP 2002043332 A [0007]

WO 03102486 A [0007]

EP 0563471 A [0007]

FR 2793015 [0008].

Claims (24)

1. Heat exchanger collection box, comprising a collecting plate (26; 46) provided with openings (28) for the insertion of heat exchange tubes (18), and a cover (44; 50; 88) delimiting distribution channels (70) that communicate with the tubes, characterized by the fact that the cover (44; 50; 88) is a metal bar having an inner face (72; 94) and an opposite outer face (74), and due to the fact that the distribution channels (70) are throats made in the thickness of the metal bar material, which flow into the inner face (72; 94), allowing matter to remain so that it closes the volume of the lid at the level of its longitudinal ends. 2. Collection box according to claim 1, characterized in that the communication steps (40, 42; 90, 92) are provided between the cover (44; 50; 88) and the collection plate (26; 46). 3. Collection box according to claim 2, characterized in that the communication steps (40, 42) are delimited by a distribution plate (38; 48) interposed between the collection plate (26; 46) and the inner face (72) of the cover (44; 50). 4. Collection box according to claim 2, characterized in that the communication steps (90, 92) are throats of the metal bar that flow on the one hand in the distribution channels (70) and on the other hand on the face inside (94) of the cover (88). 5. Collection box according to one of claims 2 to 4, characterized in that the distribution channels (70) and the communication steps (40, 42; 90, 92) are machined. 6. Collecting box according to one of claims 1 to 5, characterized in that the lid (44; 50; 88) is obtained from an extruded metal bar. 7. Collecting box according to claim 6, characterized in that the outer face (74) of the extruded metal bar is shaped so that it has a profile that involves a plurality of domes (68) in correspondence with the distribution channels (70). 8. Collection box according to one of claims 1 to 7, characterized in that the distribution channels (70) have a constant internal section throughout its length. 9. Collection box according to one of claims 1 to 7, characterized in that the distribution channels (70) have a variable internal section throughout its length. 10. Collecting box according to claim 9, characterized in that the distribution channels comprise channels (70A) of variable internal section whose bottom has a slope with an angle (A1). 11. Collection box according to claim 9, characterized in that the distribution channels comprise channels (70C) of variable internal section whose bottom has a double slope defined by two opposite angles (A2). 12. Collection box according to claim 9, characterized in that the distribution channels comprise channels (70C) of variable internal section having a main part (85) made by a first machining and a deeper central part (86) Performed by a second mechanization. 13. Collection box according to claim 9, characterized in that the distribution channels comprise channels (70C) of variable internal section made by a single mechanization, the bottom of which has an inclined part (87) defined by a slope having a angle (A3) and a part (89) of constant depth. 14. Collecting box according to one of claims 1 to 13, characterized in that the lid (50) has a single series of distribution channels (70) each extending over the entire length of the metal bar . 15. Collection box according to one of claims 1 to 13, characterized in that the cover (44) has at least two series of distribution channels (70) each of which extends to a part of the length of the metal bar. 16. Collecting box according to one of claims 1 to 15, characterized in that the distribution channels (70) have a bottom with a U-shaped transverse profile. 17. Collecting box according to claim 16, characterized in that the channels (70) have a curved longitudinal profile close to an end face (84) of the metal bar delimited by a radius (R). 18. Heat exchanger comprising a beam of tubes (18) and at least one collecting box (14, 16) according to a of claims 1 to 17. 19. Heat exchanger according to claim 18, characterized in that said exchanger comprises at least two steps and the fact that said interior sections of the distribution channels (70) allow to control and balance the flow of the fluid in the aforementioned steps (P1, P2, P3 and P4). 20. Heat exchanger according to claim 19, characterized in that it is made in the form of an evaporator. 21. Method of manufacturing a collector box for heat exchanger according to one of claims 1 to 17, characterized in that it comprises the following operations:

to)

make a collector plate (26; 46) which includes openings (28) to accommodate tubes;

b)

make means of distribution that they involve communication steps (40, 42; 90, 92);

C)

make a cover (44; 50; 88) from of a metal bar that has an inner face (72; 94) and a opposite outer face (74), machining distribution channels (70) in the form of throats obtained by machining the metal bar according to the longitudinal direction of this which flow into said inner face allowing matter to remain so that the volume of the lid at the level of its longitudinal ends; Y

d)

assemble the cover (44; 50; 88) in the collector plate (26, 46) with interposition of the means of distribution so that the communication steps (40, 42; 90, 92) lead on the one hand to the distribution channels (70) and on the other hand in the openings (28) of the collecting plate (26; 46).

22. Method according to claim 21, characterized in that the operation b) comprises the preparation of a distribution board (38; 48) that delimits the communication steps (40, 42) and that the operation d) comprises the interposition of the distribution plate (38; 48) between the collector plate (26; 46) and the inner face (72) of the cover. 23. Method according to claim 21, characterized in that the operation b) comprises the realization of the communication steps (90, 92) in the form of throats made by machining according to the transverse direction of the metal bar, flowing through a part in the distribution channels (70) and on the other hand in the inner face (94) of the cover and that the operation d) comprises the direct assembly of the collecting plate (28; 46) against the inner face (94) of the cover (88). 24. Method according to one of claims 21 to 23, characterized in that the operation c) comprises the preparation of an extruded metal bar and the mechanization of the channels (70) by means of a suitable multi-stage rotary tool (78) to simultaneously mechanize the channels in at least a part of the length of the metal bar.