EP1459030A1

EP1459030A1 - Circuit element for heat exchanger, in particular for motor vehicle and resulting heat exchanger

Info

Publication number: EP1459030A1
Application number: EP02801172A
Authority: EP
Inventors: Jean-Louis Laveran; Jacques Hoffnung; Jérôme GENOIST
Original assignee: Valeo Thermique Moteur SA
Current assignee: Valeo Systemes Thermiques SAS
Priority date: 2001-12-28
Filing date: 2002-12-23
Publication date: 2004-09-22
Also published as: US7337833B2; JP2005513409A; FR2834336A1; WO2003056268A1; US20040244955A1; FR2834336B1; AU2002364873A1

Abstract

The invention concerns a hydraulic circuit element (20) for heat exchange between a first fluid and a second fluid, defining a path for the first fluid, and comprising at least a tube (22) having two ends and at least an end fitting (24) at one of said ends of the tube (21), said end fitting including at least a communication passage (28b) defining the first fluid path. The invention also concerns the heat exchanger obtained by stacking circuit elements (20). Said heat exchanger can be used in particular in motor vehicles.

Description

Circuit element for a heat exchanger, in particular for a motor vehicle, and a heat exchanger thus obtained.

The invention relates to a circuit element for a heat exchanger, in particular a heat exchanger intended for the equipment of a motor vehicle.

More specifically, it relates to a circuit element for heat exchange between a first fluid and a second fluid, defining a path for the first fluid.

It also relates to the heat exchangers obtained from these circuit elements.

Such exchangers generally consist of a bundle of parallel tubes mounted between two manifolds, the tubes alternating with spacers, for example of the corrugated type. Exchangers are also known which consist of a single tube folded in the form of a coil. These exchangers have many applications and can in particular be used as condensers in air conditioning circuits of motor vehicles.

However, these known exchangers have many drawbacks. With regard to the technology of tube and manifold exchangers, the latter increase the size of the exchangers without increasing their performance. The manifolds do not improve the heat exchange and cause a loss of space. On the other hand, the exchanger must be rectangular in shape because of the presence of the manifolds. In addition, to create passes in the exchanger, it is necessary to add and integrate additional parts, the partitions, in the manifolds.

Finally, the manufacture of these exchangers is difficult, because it is necessary to punch and puncture the collector plates. It is difficult to thread thin tubes in a large collector with small tolerances.

The coil exchangers do not allow passes to be made. Their manufacture is long because it is difficult to industrialize. It takes a long time to make a coil with a machine. As a result, exchangers manufactured with this technology have a higher cost price than tube and manifold exchangers.

The present invention relates to a hydraulic circuit element for a heat exchanger which overcomes these drawbacks known from the prior art.

To this end, each hydraulic circuit element of the exchanger comprises at least one tube, generally flat, having two ends and at least one end piece fixed to one of said ends of the tube, said end piece comprising at least one communication passage defining the course of the first fluid. A circuit element of this type and the heat exchangers which include such elements have many advantages.

The main advantage is flexibility. Indeed, the tips can be of very diverse configurations. An exchanger can consist of a stack of different circuit elements. Thus, according to the invention, both a coil condenser and a parallel tube condenser can be produced. It is also possible to produce a parallel tube exchanger comprising passages without having to integrate additional parts, such as partitions. For this, it suffices to use circuit elements, the ends of which may or may not have communication passages assembled in an appropriate manner.

Furthermore, the invention allows a reduction in the size of the exchanger by optimizing the effective surface from the point of view of heat exchange by replacing the manifolds with less bulky ends.

It also makes it possible to eliminate the punched collecting plates and the mounting of the tubes in the perforations of small dimensions and low tolerance of these collecting plates. The circuit elements can be delivered equipped with their end pieces, which facilitates the assembly of one exchanger. This eliminates the mechanical function of introducing tubes into drilled manifolds. It is sufficient to assemble the tubes with end caps whose dimensions are the same as those of the tubes. Next, the circuit elements are stacked. There is therefore a great simplicity of assembly and manufacture. It is possible to produce an exchanger comprising tubes of different lengths. It is thus possible to adapt the shape of the exchanger to the space available on the vehicle.

In addition, fixing lugs can be fixed on the end pieces before or after the brazing of the entire exchanger. The mounting lugs do not require any particular adaptation of the heat exchanger bundle or the end fittings.

An exchanger of any type can be produced in accordance with the invention, namely a radiator, a condenser, an evaporator or an air cooler.

In a preferred embodiment, the one or more tubes are generally flat and / or the one or more end pieces are fixed to the ends of the one or more tubes.

In a simple embodiment, the circuit elements consist of a single tube comprising an end piece at each of its two ends.

In another, more complex embodiment, the circuit elements consist of several tubes, an intermediate nozzle being present between two successive tubes.

The circuit elements can thus consist of two or three tubes, or even more.

The circuit elements made up of several tubes can have a rectilinear shape or a broken line shape. In one embodiment, said tip or at least one of said tips of the exchanger consists of a folded sheet metal strip to form two branches of equal length.

In another embodiment, said tip or at least one of said tips consists of a folded sheet metal strip to form two branches of unequal length.

Additional or alternative features of the circuit element of the invention are listed below:

said tip or at least one of said tips has two bosses aligned on the longitudinal axis of said tube or tubes; - Said tip or at least one of said tips has two bosses aligned in a direction perpendicular to the longitudinal axis of said tube or tubes; said tip or at least one of said tips has two pairs of bosses, the two bosses of the same pair being aligned in a direction perpendicular to the longitudinal axis of said tube or tubes; said tube has a hole opening laterally at one and / or the other of its ends allowing the passage of the fluid between the interior of the tube and the fluid communication passages defined by said end pieces; in such a case, said longitudinal orifices of the tube, provided opening, may be closed by a said nozzle, the circulation of the fluid then being effected by said holes opening laterally.

In another aspect the invention relates to a heat exchanger, in particular for a motor vehicle, comprising a stack of circuit elements as defined previously, which communicate via said end pieces to allow said first fluid to pass between said circuit elements.

Advantageously, some of the end pieces have bosses by which the circuit elements come into contact when they are stacked, so that the bosses of a circuit element rest on the bosses of the adjacent circuit elements.

Advantageously, the exchanger comprises an inlet pipe and / or an outlet pipe comprising a flattened end adapting to the space available between the ends of two adjacent circuit elements.

According to yet another advantageous characteristic of the invention, the heat exchanger comprises fixing lugs fixed to the ends of the circuit elements.

Other characteristics and advantages of the present invention will appear on reading the following description of exemplary embodiments given by way of illustration with reference to the appended figures. In these figures:

- Figure 1 is a view of a tube and manifold exchanger according to the prior art;

Figure 2 is a view of a coil exchanger according to the prior art;

- Figure 3 is a perspective view of an exchanger according to the present invention; - Figure 4 is a partial sectional view of the right part, according to the figure, of the exchanger shown in Figure 3;

- Figures 5 to 7 are various views which show a nozzle having branches of equal length intended to constitute a circuit element forming part of an exchanger according to the present invention;

- Figure 8 is a perspective view of the end of a tube having a communication hole;

Figure 9 is a perspective view of a tip having two bosses aligned longitudinally with respect to the axis of the circuit element;

- Figure 10 is a perspective view of a nozzle having two bosses aligned in a direction perpendicular to the longitudinal axis of the circuit element

Figure 11 is a perspective view of a nozzle similar to that shown in Figure 10, but having a communication channel between the two bosses;

FIG. 12 is a perspective view of a nozzle comprising two pairs of bosses:

- Figure 13 is a perspective view of a nozzle having branches of unequal lengths; - Figure 14 and Figure 15 are views of a nozzle having branches of unequal length having bosses connected by a communication channel;

- Figure 16 is a partial perspective view of an exchanger according to the present invention;

- Figure 17 shows an example of application of circuit elements comprising end pieces having branches of unequal lengths;

- Figure 18 shows the layout of the inlet and outlet pipes in a heat exchanger according to the present invention;

- Figure 19 is a perspective view of an exchanger consisting of a stack of circuit elements consisting of two tubes connected by an intermediate nozzle;

- Figure 20 is a perspective view of an exchanger whose circuit elements consist of three tubes assembled by intermediate end pieces;

Figures 21 to 23 are perspective views which show the production of various variants of the intermediate nozzle for exchangers such as those shown in Figures 19 and 20;

Figures 24 and 25 illustrate two alternative embodiments of the tube shown in Figure 8;

FIG. 26 illustrates along a longitudinal sectional plane the tube of FIG. 8, equipped with a nozzle such as that of FIG. 6. FIG. 1 shows a conventional type heat exchanger comprising a bundle of flat tubes interposed between two manifolds. The bundle 2 is formed from a multiplicity of flat tubes 4 arranged parallel to one another and alternating with corrugated inserts 6. These inserts are formed from a metal strip which is deformed to form undulations. An interlayer 6 is disposed between two adjacent tubes 4 and comes into respective contact with these two tubes 4 by end regions of the corrugations.

The tubes 4 of the bundle are inserted, at each of their ends, in perforations made in collecting plates 8, also called collectors. The collector plates 8 are closed by a cover 9 to form fluid boxes 10, for example water or air boxes.

To allow the mounting of the tubes 4, it is necessary to punch the tube plates 8 and to puncture them. The assembly of the tubes is not an easy operation.

The presence of the manifolds 10 increases the size of one exchanger without increasing its performance.

To create passes in the exchanger, it is necessary to integrate partitions 12 which divide the manifolds 10 into separate chambers.

Another known type of exchanger is shown in FIG. 2, namely a coil exchanger. The exchanger consists of a single tube 14 folded in the shape of coil. Corrugated spacers 6 can be arranged between the round trips of the coil. An exchanger of this type is simpler than the tube bundle exchanger and manifold boxes shown in Figure 1. It has fewer parts. However, the industrialization of its manufacture is delicate and in total, a coil exchanger is more expensive to manufacture than a tube bundle exchanger and manifold boxes. In addition, an exchanger of this type cannot be arranged so as to include passes.

There is shown in Figure 3 an external perspective view of a heat exchanger according to the present invention and in Figure 4 a sectional view of the right part. It consists of a stack of circuit elements 20. Each circuit element 20 consists of at least one tube 22 having two ends. In the example shown, the circuit elements comprise only one tube, but as will be described later, a circuit element can comprise several tubes. A tip 24 is fixed to each end of the tube 22. In the example shown, the tips each have two bosses 26

(also called basins) of frustoconical shape. Each boss or bowl 26 has a flat bottom 28. The flat bottoms 28 of the bosses of a tip of a circuit element 20 come to bear on the flat bottoms of the bosses of the adjacent circuit elements. As a result, the various circuit elements 20 which constitute the exchanger shown in FIG. 3 are supported one on the other by means of the flat bottoms of the bosses 26 of the end pieces of each of the circuit elements.

The flat bottoms 28 of the bosses 26 can be full, that is to say have no perforation. In that case they do not allow any circulation of the first fluid which circulates in the tubes 22 of the exchanger between two adjacent circuit elements 20. On the contrary, the flat bottoms 28 may have perforations 27 facing each other so that the first fluid can pass from one modular element to another.

In FIG. 3, the flat bottoms 28 closed by a small circle 28a shown in hatched perspective are shown diagrammatically, and the perforated flat bottoms, allowing the passage of the fluid, by a small circle 28b without hatching. Thus, in the example shown in perspective in Figure 3 and in partial sectional view in Figure 4, the first fluid enters the exchanger at the upper right of the exchanger, as shown by the arrow 30. The flat bottom of the boss 26 situated opposite the entry of the fluid into the exchanger being closed (closed bottom 28a), the first fluid moves from right to left (arrow 32) and runs through the upper tube 22 of the exchanger. The fluid reaches the nozzle 24 located on the left part (according to Figure 3) of the upper tube 22 of the exchanger. The upper boss 26 has a closed flat bottom 28, while the lower boss of the end piece 24 has a flat bottom 28b open. The fluid can therefore pass from the upper circuit member 20 ^'the circuit element immediately below, as indicated by the arrow 34. The first fluid then traverses the second circuit element 20 from left to right according to Figures 3 and . At the right of the second circuit member end 20 it passes through the lower loop member (arrow 36) through perforations 28b provided in the bosses flat bottoms as described ^'above. The fluid thus performs a series of back and forth in the tubes of the circuit elements from right to left and from left to right, exactly as in a coil exchanger of the type shown in FIG. 2. The first fluid leaves the exchanger on the left side of the latter, as shown by arrow 38.

During its alternative course in the tubes 22 of the exchanger, the first fluid is in heat exchange relation with a second fluid which circulates in a conventional manner perpendicular to the bundle of the tubes 22. In addition, in a conventional manner, corrugated spacers 6 can be arranged between the tubes 22 of the exchanger as shown diagrammatically in FIG. 3.

A heat exchanger has thus been produced in a simple manner allowing the exchange of heat between a first fluid, generally a liquid and a second fluid, generally a gas, in particular atmospheric air, constituted by a superposition of circuit elements 20 consisting of tubes at the ends of which are fixed end pieces some of which have communication passages 28b and others have no communication passage. The superimposition of the circuit elements defines the path of the first fluid.

In the example shown in Figures 3 and 4, an exchanger has been formed which defines a path of the first fluid identical to that of a coil exchanger. However, the realization of the exchanger allows great flexibility and very diverse types of exchangers can be obtained by a simple superposition of circuit elements according to the invention.

It is important to note that the presence or absence of perforations 27 in the bottom 28 of the bosses 26 allows very simple passes in the exchanger. he it is not necessary to provide additional added parts such as the partition walls 12 (see FIG. 1) usually present to constitute divisions in the manifolds 10 of the exchangers of conventional type.

When it is desired to make a separation between two chambers in order to carry out passes in a heat exchanger, it suffices to provide a circuit element the end pieces of which do not include perforation at the appropriate place. Separate chambers are thus produced without the presence of a manifold. This results in a reduction in the number of parts and a simplification of the exchanger.

There are shown in Figures 5 to 7 different views of a nozzle 24 for a circuit element 20 of a heat exchanger according to the invention, in particular of a heat exchanger shown in Figures 3 and 4 As can be seen in FIG. 5, the end pieces are produced by stamping and folding a metal strip, preferably aluminum, comprising two branches 31. The stamping makes it possible to produce the two bosses 26 and possibly the perforations 27 of the flat bottom 28 of the bosses 26, if these perforations exist. In addition, a deep-drawn 42 is formed in the aluminum strip between the branches 31 in which the two bosses 26 are formed. The deep-drawn 42 forms the bottom of the end-piece. It prevents the liquid from escaping in the axial direction of the tube after assembly of the circuit element. The sheet metal strip is then folded back so as to bring the two parts comprising the stampings together, as can be seen in FIG. 6. In Figure 7, the two branches 31 have been fully folded and the tip is shown finished. It is then assembled, for example by clipping, fitting or crimping on a tube 22 before brazing. Perforations 44 and 45 facilitate the brazing of the end piece on the end of the tube 20.

Thanks to this manufacture, the problem which is encountered in conventional tube bundle exchangers and manifold boxes is resolved, namely to thread a small tube into a large collector with small holes and tight tolerances. According to the invention, this problem is eliminated. It suffices to assemble end pieces 24 on tubes 22 of the same dimensions. The mechanical function of introducing tubes into drilled manifolds is eliminated. This results in an extreme simplification of the assembly and manufacture of the exchanger.

The manufacture of the exchanger will therefore include a production station to produce the tubes, a press to produce the nozzles and an automatic machine to insert the nozzles on the tubes. We then go directly to the assembly of the exchanger by superimposing the circuit elements thus manufactured with the possible interposition of corrugated spacers 6. The assembly is then assembled by brazing.

FIG. 8 shows a perspective view of the end of a particular embodiment of a tube 22 intended for constituting a circuit element according to the invention. As can be seen, this tube is a multi-channel tube. It has seven channels 46 separated by six partition walls 48. Such a tube is intended, for example, to contain a pressurized fluid. The partition walls 48 strengthen the tube and prevent it from bulging under the pressure of the fluid. In addition, the particularity of this tube lies in the fact that it has a circular through hole 50 at one of its ends or at its two ends (only one end shown). Thus, the communication between the tube and the nozzle can be ensured in two different ways. In a first embodiment, the end piece 24 is simply clipped to the free end of the tube and the fluid leaves the tube or enters it through the end of the latter. In this case, the tube has no perforations 50. In another embodiment, the end pieces 24 are fitted on the end of the tube in such a way that the hole 50 is located substantially opposite the perforations 27 of the bosses 26. In this In this case, the communication between the tube and the end piece takes place through the perforations 50. The bosses 26 are, for example, in the axis of the perforations 50.

In this case, the longitudinal hole (s) of the tube 22 can be closed by the end piece 24, more precisely by the deep end 42 constituting the bottom of said end piece.

There are shown in Figures 9, 10, 11 and 12 various embodiments of a tip shown in Figures 5 to 7. The tip of Figure 9, instead of having only a boss 26 on each of its branches 31, like the tip of FIGS. 5 to 7, has two, that is to say four bosses in total. These tips are made in the same way as the tip of Figure 5, namely by stamping and folding an aluminum strip. The flat bottoms 28 of the end pieces 26 may or may not be perforated depending on the characteristics of the exchanger to be produced. There is shown in Figure 10 a perspective view of a tip in progress. This nozzle has two pairs of bosses 26 on each of its branches, like that of FIG. 9. However, the bosses 26, instead of being arranged in the axis of the circuit element, that is to say say in the axis of the tube 22, as the bosses of the nozzle shown in Figure 9, are arranged one next to the other. In other words, they are arranged such that their axis is on a line perpendicular to the longitudinal axis of the circuit element. A tip of this type can be applied to a tube comprising several channels, for example two channels or more than two channels. Some of the channels of the tube are in communication with the left part of the end piece, while the other channels of the tube are in communication with the right part of the end piece (according to FIG. 10). Or, in another embodiment, two different tubes 22 can be adapted on a single end piece such as that shown in FIG. 10.

There is shown in Figure 11 a perspective view of a nozzle 24 similar to that of Figure 10. It is distinguished however by the fact that the two bosses 26 visible in the upper part of Figure 11 are connected by a communication channel 54. The presence of the channel 54 makes it possible to establish, as required, communication between the interior volumes of the two stampings 26. A communication channel 54 can be provided on one of the faces of the tip or on both sides. The channel 54 is preferably produced by stamping at the same time as the stampings 26.

There is shown in Figure 12 a perspective view of a larger tip having four bosses 26 on each of its branches, a total of eight bosses. The bosses 26 are distributed in two pairs, each pair being aligned on the longitudinal axis of the tube.

FIG. 13 shows a perspective view of another embodiment of a nozzle according to the present invention. It differs from previous tips in that it has two branches 31 or legs of different lengths. Indeed, the end pieces shown in Figures 5 to 12 all have branches of the same length which overlap one another when they are fully folded as can be seen for example in Figure 7. The end piece shown in Figure 13 has two legs or branches 31 of different lengths. Each branch has a perforated stamp 26, so that they do not overlap each other entirely. In addition, it can be seen that the longest branch comprises a communication channel 54, preferably formed by stamping the sheet metal strip at the same time as the end stamped 42 and the two bosses 26.

There is shown in Figures 14 and 15 an alternative embodiment of the tip of Figure 13. It is distinguished in that the longest branch 31 has two stamps 26 instead of one. One of the stamps 26 of the longest branch is located opposite the stamp of the shortest branch, while the stamp 26 located at the end of the longest branch has no screws to screw. In addition, a communication channel 54 connects the stampings 26 of the long branch.

FIG. 16 shows a possible application of end pieces having branches 31 of unequal lengths like those shown in FIGS. 13 to 15. The end pieces 24 of the circuit elements 20 located at the upper part and at the lower part of the exchanger have branches 31 of equal length. Likewise, the end pieces 24 of the two circuit elements 20 located in the center of the exchanger also have tabs of equal length. On the other hand, two particular ends, referenced 24 ′, have branches of unequal lengths. The end piece 24 ′ located at the upper part of the exchanger ensures the transition between the four longer tubes 22 located at the upper part of the exchanger and a shorter tube. In the same way, the end piece 24 'situated at the lower part of the exchanger makes it possible to ensure a transition between the four longer tubes 22 located at the lower part of the exchanger and a shorter dimension tube . This leaves a free space 25 in the body of the exchanger. This characteristic makes it possible, for example, to adapt the geometric shape of the exchanger to the space available in the vehicle. This facilitates its implementation and constitutes an advantage compared to conventional exchangers which must necessarily be rectangular in shape because of the presence of the manifolds 10 (FIG. 1).

There is shown in Figure 17 a partial schematic perspective view of another tip application comprising. branches of unequal length. The space left free by the tubes 22 of shorter lengths allows the installation of a bottle 56, for example a condenser bottle.

FIG. 18 shows a partial view in elevation of a heat exchanger according to the present invention. This view shows in particular the embodiment of the inlet 58 and outlet 60 pipes of the first fluid. These tubes are interposed between the ends of two circuit elements. On the side of the inlet 58 and outlet 60 pipes, the end pieces 24 do not have a boss 26. Thus, the end of the pipes which are flattened can be inserted so as to conform exactly to the space available between two pipes. neighbors.

It will also be noted in FIG. 18 the end cheeks 62 constituted for example by a sheet folded in a U shape and the presence of fixing lugs 64 and 66 fixed on the end pieces 24 of certain circuit elements of the exchanger, for example by brazing. Finally, it will be noted that two particular end pieces, referenced 24 ′, have branches of unequal length so as to create a transition between longer tubes and shorter tubes, which creates a space 25 between the tubes of the exchanger, as described above with reference to FIGS. 16 and 17.

In the embodiments described above, the exchanger consists of circuit elements comprising a single tube 22. The circuit elements which constitute the exchanger of the invention can also comprise two tubes (FIG. 19) or more than two tubes ( Figure 20), for example three or more tubes. In this case, each circuit element 20 comprises two different types of end pieces: on the one hand, the end pieces or end pieces 24 described above, on the other hand, the intermediate ends designated by the reference 124. The intermediate ends are distinguish from end fittings by the fact that they are connected to two separate tubes instead of being fixed to the end of a single tube. The circuit elements of the exchanger shown in FIG. 19 comprise a single intermediate end piece 124. The circuit elements of the exchanger shown in FIG. 20 has two intermediate ends 124.

FIG. 21 shows a perspective view which illustrates the production of an intermediate end piece 124. The intermediate end pieces, like the end pieces, are obtained from a sheet, preferably an aluminum sheet. Initially, this sheet is cut to obtain a Y shape (not shown). The Y shape is folded in half and the edges are folded so as to obtain a closed shape like that shown in FIG. 21. A tube 22 is then fitted at each of the ends of this closed shape. The intermediate end pieces may have an angle as shown in FIGS. 19, 20 and 21. However, the intermediate end pieces could also be straight.

The intermediate nozzle shown in Figure 21 is simple in that it has no connection for the entry or exit of the first fluid. However, an intermediate nozzle may also include bosses 26 which allow the entry or exit of the first fluid at the connection between two tubes of a particular circuit element 20, as shown in FIG. 22. The intermediate element 124 may also include several bosses 26, for example two pairs of bosses as shown in perspective in FIG. 23.

The tube 22 shown in Figure 24 is similar to the tube 22 of Figure 8, except that it is made by shaping a folded sheet 70 and not by extrusion. This sheet 70 has two longitudinal edges 72 which are joined together. Furthermore, this sheet has internal folds 74 capable of defining partitions delimiting seven internal channels 46. The tube also has a circular through hole 50 similar to that of the tubes in FIG. 8.

The tube 22 shown in FIG. 25 is also similar to that of FIG. 8. It is also a flat tube produced, in the example, by extrusion. This tube internally houses a corrugated insert 76, which makes it possible to define a multiplicity of circulation channels 46 inside the tube.

The circuit element of the invention can be used to produce different types of heat exchanger and in particular condensers for air conditioning installations of motor vehicles.

Claims

1. Hydraulic circuit element (20), for the exchange of heat between a first fluid and a second fluid, defining a path for the first fluid, characterized in that it comprises at least one tube (22) having two ends and at least one end piece (24) at one of said ends of the tube (22), said end piece comprising at least one communication passage (28b) defining the path of the first fluid.

2. Circuit element according to claim 1, characterized in that said tube(s) (22) are generally flat and/or said end piece(s) (24) are fixed to the ends of said tube(s) (22.

3. Circuit element according to one of claims 1 and 2, characterized in that it comprises a single tube (22) comprising a terminal end (24) at each of these ends.

4. Circuit element according to one of claims 1 and 2, characterized in that it is made up of several tubes (22), an intermediate end piece (124) being present between two successive tubes (22).

5. Circuit element according to claim 4, characterized in that it has a rectilinear shape.

6. Circuit element according to claim 4, characterized in that it has a broken shape.

7. Circuit element according to one of claims 1 to 6, characterized in that said end piece (24) or at least one said end pieces consist of a strip of sheet metal folded to form two branches (31) of equal length.

8. Circuit element according to one of claims 1 to 6, characterized in that said end piece (24) or at least one of said ends consists of a strip of sheet metal folded to form two branches (31) of length uneven.

9. Circuit element according to one of claims 1 to 8, characterized in that said end piece (24) or at least one of said end pieces comprises two bosses (26) aligned on the longitudinal axis of said tube or tubes (22). ).

10. Circuit element according to one of claims 1 to 8, characterized in that said end piece (24) or at least one of said ends comprises two bosses (26) aligned in a direction perpendicular to the longitudinal axis of the or of said tubes (22).

11. Circuit element according to one of claims 1 to 8, characterized in that said end piece (24) or at least one of said ends comprises two pairs of bosses (26), the two bosses of the same pair being aligned in a direction perpendicular to the longitudinal axis of said tube(s) (22).

12. Circuit element according to one of claims 9 to

11. characterized in that a communication channel (54) is formed in at least one of the branches of the end piece (24) to establish circulation of the first fluid between the bosses (26).

13. Heat exchanger, in particular for a motor vehicle, comprising a stack of circuit elements (20) according to one of the preceding claims communicating via said end pieces (24) to allow passage of said first fluid between said circuit elements.

14. Heat exchanger according to claim 13, characterized in that some of the end pieces (24) have bosses (26) through which the circuit elements (20) come into contact when they are stacked, such that the bosses (26) of a circuit element (20) rests on the bosses (26) of adjacent circuit elements (20).

15. Heat exchanger according to one of claims 13 and 14, characterized in that it comprises an inlet tubular (58) and/or an outlet tubular (60) having a flattened end adapting to the space available between the ends of two adjacent circuit elements (20).

16. Heat exchanger according to one of claims 13 to 15, characterized in that it comprises two fixing lugs (64, 66) fixed to the end pieces (24) of the circuit elements (20).