FR2751403A1 - Counterflow heat exchanger flat tube - Google Patents

Abstract

The flat tube is cut and folded from sheet metal to forming two longitudinal adjacent edges (26,28) folded toward a large surface (16) of the tube (10). This delimits two parallel channels (12,14) for the counterflow of a fluid (F1,F2). The two separated folded edges form a free space. The large surface of the tube has, at each tube end, a notch (42) located in the free space and extending over a length in the tube axial direction. Each end of the tube forms two distinct flat and aligned ends (46,48). The rectangular notch has a width equal to that of the free space. Each tube end is received in a heat exchanger plate manifold. The axial length of the notch is greater than the thickness of the plate manifold.

Description

Counterflow flat tube for heat exchanger
The invention relates to a flat tube suitable for being part of a heat exchanger such as, for example, a radiator for cooling a motor vehicle engine.

It relates more particularly to a flat tube suitable for use in a heat exchanger in which a fluid, for example a cooling fluid of the engine of the motor vehicle, flows against the current in two layers which extend parallel to one another and in parallel with two front faces of the heat exchanger.

 I1 is known, for this, to use two rows of tubes to respectively form the two layers and to connect the ends of the tubes to two fluid boxes.

One of the fluid boxes is then divided by a longitudinal partition to form an inlet compartment and an outlet compartment, while the other fluid box is devoid of partition.

 As a result, the fluid enters the inlet compartment of the first fluid box, circulates in a first row of tubes in a given direction of circulation to form a first layer of fluid, reaches the second fluid box and also that -this to then circulate in the second row of tubes in an opposite direction of circulation, to form a second sheet against the current and finally reach the outlet compartment of the first fluid box.

This known solution requires the use of two rows of tubes and, consequently, the use of two manifold plates, associated respectively with the two fluid boxes, and each comprising two rows of holes for receiving the ends of the tubes. This therefore requires complex assembly and assembly operations.

In addition, this requires the use of generally electrowelded tubes which are expensive to produce.

Furthermore, it is known to use flat tubes each formed from a cut and folded metal sheet having two adjacent longitudinal edges folded towards a large face of the tube to delimit two parallel channels for the circulation of a fluid against -current.

 It is then possible to use a single row of tubes, since the fluid can circulate in respective first channels of the tubes to form the first layer of fluid and in respective second channels of tubes to form the second layer of fluid.

A flat tube with two parallel channels of this type is known from the publication FR-A-2,572,797.

However, this known solution requires special arrangements to ensure the tight connections of the first circulation channels and second circulation channels respectively with the inlet compartment and the outlet compartment of the first fluid box. It should also be noted that, in the abovementioned publication, it is not necessary to provide a second fluid box, but a bottom plate to make a U-shaped turn in the circulation of the fluid in each of the flat tubes.

There is also known, from publication EP-A-0 302 232, a flat tube for heat exchanger which is similar to that described in the abovementioned publication.

This flat tube has one or more internal partitions serving to ensure its mechanical strength and dividing the tube into several parallel channels for the circulation of a fluid, but always in the same direction of circulation.

In the two aforementioned publications, the folded longitudinal edges come into mutual contact in order to each time form a partition between two adjacent channels. I1 follows that the end of such a tube can only be received in a single hole of a manifold plate, which poses problems, not only to seal the connection of the end of the tube with the edges of the corresponding hole, but also to ensure the watertight connection of the longitudinal partition of the fluid box. Indeed, this longitudinal partition must come to be sealed in connection with the collector plate in order to contribute to delimiting the inlet compartment and the outlet compartment, which must be in sealed communication respectively with the first channels and the second channels of the flat tubes. of the beam.

The object of the invention is in particular to overcome the aforementioned drawbacks.

To this end, it offers a flat tube for heat exchanger, of the type comprising a cut and folded metal sheet having two adjacent longitudinal edges folded towards a large face of the tube to delimit two parallel channels for the circulation of a counter-current fluid. .

According to the invention, the two folded longitudinal edges are spaced from each other to provide between them a free space of selected value, while the large face of the tube has, at each end of the tube, a notch located in the region of the free space and extending over a length chosen in the axial direction of the tube, so that each tube end forms two distinct and aligned flat ends.

As a result, each end of the tube forms two separate end pieces which can be received respectively in two adjacent holes of a manifold plate connected to a fluid box of a heat exchanger.

The invention thus makes it possible to use a single row of flat tubes, which reduces assembly and component costs and also makes it possible to reduce the size of the heat exchanger.

Furthermore, the fact that each tube has two end pieces which can be received respectively in two adjacent holes of a collector plate, these two holes, which can also be called double hole ", can be dimensioned according to the two end pieces and allow a direct connection by brazing of all the tubes with the collector plates. This eliminates the need for soldering before brazing, as is necessary in the case where electro-welded tubes are used. and economical.

The notch formed at each end of the tube advantageously has a rectangular shape and has a width of value substantially equal to the value of the free space between the two folded longitudinal edges.

According to the invention, each of the tube ends is suitable for being received in a heat exchanger collector plate.

It is then expected that the length of the notch is greater than the thickness of the collector plate.

Thus, when the two ends of a tube end are introduced into a double hole of a manifold plate, these two ends protrude in the direction of the fluid box.

This allows a better sealed connection, in particular by brazing, between the tube end and the collector plate.

According to another characteristic of the invention, each of the folded edges advantageously has a generally L-shaped profile having an intermediate wing extending perpendicular to the large face of the tube and a terminal wing applied flat against the large face.

According to another characteristic of the invention, the metal sheet is advantageously made from an aluminum alloy and is coated with a solder plating.

In another aspect, the invention relates to a heat exchanger comprising a row of flat tubes as defined above, in which the ends of the tubes are connected to two manifold plates connected respectively to two fluid boxes.

Each of the manifolds has a row of double holes equal in number to that of the tubes, each double hole being dimensioned to receive the two end pieces of a tube end.

According to another characteristic of the invention, each double hole is formed of two aligned oblong holes separated from each other by a bridge of material of width substantially equal to the value of the free space comprised between the two folded longitudinal edges of a tube .

Thus, when the two ends of a tube end are fully engaged in the two oblong holes of a double hole, the bottom of the notch serves as a stop for the introduction.

According to another characteristic of the invention, the axial length of the notch of each tube end is greater than the thickness of the collector plate, so that, after assembly, the two ends of each tube protrude inside of the fluid box.

This characteristic makes it possible, as already indicated, to ensure a better connection between the ends of the tubes and the collector plates.

According to another characteristic of the invention, one of the fluid boxes comprises a partition which divides the interior of the fluid box into two parallel compartments, namely an inlet compartment communicating with the first channels of the tubes and a outlet compartment communicating with second tubes channels.

The partition has a longitudinal edge received in the respective notches of the ends of the tubes opening into the fluid box.

This ensures better guidance of the partition, the longitudinal edge of which is thus rigorously positioned relative to the corresponding collecting plate.

In the description which follows, given solely by way of example, reference is made to the appended drawings, in which - FIG. 1 is a side view of a flat tube according to the invention; - Figure 2 is an end view of the flat tube of Figure 1; - Figure 3 is a sectional view, on an enlarged scale, along the line III-III of Figure 1; - Figure 4 is a perspective view, with parts broken away, of a heat exchanger comprising a multiplicity of flat tubes according to the invention; - Figure 5 is another perspective view, broken away, of the heat exchanger of Figure 4; - Figure 6 is a detail, on an enlarged scale, of Figure 4; and - Figure 7 is a partial perspective view of the header plate of the exchanger of Figure 6, before assembly of the heat exchanger.

We first refer to Figures 1 to 3 which show a flat tube 10 formed from a metal sheet, for example aluminum or aluminum alloy, cut and folded on itself so as to delimit two channels parallel 12 and 14 for the circulation of a countercurrent fluid, as shown by the arrows F1 and F2 in FIG. 1.

The tube 10 has a first large flat face 16, two small substantially semi-circular faces 18 and 20, and a second large flat face formed by two marginal strips 22 and 24 of the sheet. These two marginal strips 22 and 24 are extended by two folded edges 26 and 28 distant from each other and connected to the large face 16 to delimit the two aforementioned channels. Each of the folded edges 26, 28 has a generally L-shaped profile (FIG. 3) having an intermediate wing 30 respectively 32 extending perpendicularly to the large face 16 and a terminal wing 34 respectively 36 applied flat against the large face 16 and connected to it.

In the example, the metal sheet from which the tube 10 is formed is provided with a solder plating, on at least one of its faces, which makes it possible to ensure a connection by soldering the end wings 34 and 36 and of the large face 16.

The intermediate wings 30 and 32 of the folded edges 26 and 28 are spaced from each other and provide between them a free space E of selected width (Figure 3).

The flat tube 10 has two opposite ends 38, 40 (Figure 1) which include respective notches 42 and 44 of generally rectangular shape (Figure 1). Each of these notches is located in the region of the free space and extends over a chosen axial length L (FIG. 1) in the axial direction of the tube. Furthermore, the width 1 of each of the notches is substantially equal to the value of the free space E comprised between the two folded longitudinal edges of the tube.

it follows that each end of the tube forms two flat, distinct and aligned ends, namely two ends 46 and 48 for the end 38, and two ends 50 and 52 for the end 40 (FIG. 1).

Referring now to Figures 4 and 5 which show a heat exchanger, such as a radiator for cooling a motor vehicle engine, formed from a multiplicity of flat tubes 10 as defined above.

The heat exchanger shown in Figures 4 and 5 comprises a row of flat tubes 10 between which are disposed each time corrugated spacers 54 forming fins.

The ends 38 of the flat tubes 10 are received in a collecting plate 56 which is itself connected, at its periphery, to a fluid box 58.

The collector plate 56 (FIG. 1) is produced from a cut and stamped metal sheet having a generally rectangular shape (FIG. 7). This sheet includes a row of double holes 60 whose number and spacing correspond to those of the flat tubes 10. Each double hole 60 is formed by two aligned oblong holes separated from each other by a bridge of material 62 whose width P is substantially equal to the value of the free space E between the two folded edges of a flat tube.

Furthermore, the axial length L of each of the notches 38 or 44 of a tube is much greater than the thickness e of the collecting plate 56 (FIG. 7).

The double holes 60 are dimensioned as a function of the dimensions of the respective ends 46 and 48 or 50 and 52.

Thus, when the two ends 46 and 48 of a tube 10 are introduced into a double hole 60, these two ends protrude from the collector plate 56 and protrude in the direction of the fluid box 58, as can be seen better on Figure 6.

The collector plate 56 shown in FIGS. 6 and 7 has, at each end, a folded edge 64 which is adapted to cooperate with the fluid box 58.

The latter has a flat bottom 66 leading to a peripheral edge 68 which is folded against a peripheral edge 70 of the collector plate 56 to ensure their tight connection.

The fluid box 58 internally receives a longitudinal partition 72 of generally rectangular shape (FIGS. 4 to 6) which is suitable for being disposed between the flat bottom 66 of the fluid box 58 and the collecting plate 56. This partition has a longitudinal edge 74 (FIG. 6) which bears against the collecting plate 56 and which is received in the respective notches 42 of the ends 38 of the tubes. The partition 72 also has an opposite longitudinal edge 76 which bears against the bottom 66 of the fluid box 58.

This fluid box is thus divided into two compartments, an inlet compartment 78 into which the end fittings 48 open, and an outlet compartment 80 into which the respective end fittings 46 of the tubes open.

The tube bundle is connected, at its other end, to a collecting plate 82 (FIGS. 4 and 5) similar to the collecting plate 56. This collecting plate also includes a row of double holes in which the respective end pieces 50 and 52 are engaged. of each tube 10. This collector plate 82 is connected, at its periphery, to a fluid box 84, similar to the fluid box 58, but which does not have a longitudinal partition.

The fluid box 58 is provided with two pipes 86 and 88 respectively serving for the inlet (arrow F1) and the outlet (arrow F2) of a fluid, for example a coolant of an internal combustion engine of motor vehicle.

The fluid enters through the inlet tubing 86 into the inlet compartment 78, then flows through the respective channels 14 of the tubes 10, reaches the interior of the fluid box 84, then flows through the respective channels 12 of the tubes 10 , to reach the outlet compartment 80 and leave the heat exchanger through the outlet pipe 88.

The various parts making up the heat exchanger of FIGS. 4 and 5 are advantageously formed from metal sheet of the same material, in particular an aluminum alloy, coated with a solder plating.

This allows the connection of the various constituent parts of the heat exchanger in a single operation in a brazing furnace, at the same time sealing the connection of the tubes with the collector plates and the fluid boxes.

 It should be noted that the notches provided at the respective ends of the tubes serve first of all to receive the collector plates by forming a stop for the introduction and in addition to receive a partition, in the case where the collector plate is associated with a fluid box used for the inlet and outlet of the fluid.

Of course, the invention is not limited to the embodiment described above by way of example and extends to other variants. In particular, it is not limited to the use as a heat exchanger for cooling a motor vehicle engine.

Claims (10)

Claims 1. Flat tube for heat exchanger, comprising a cut and folded metal sheet having two adjacent longitudinal edges (26, 28) folded towards a large face (16) of the tube (10) to delimit two parallel channels (12, 14) for the circulation of a counter-current fluid (F1, F2), characterized in that the two folded longitudinal edges (26, 28) are spaced from each other to provide between them a free space (E) of chosen value, and in that the large face (16) of the tube comprises, at each end (38; 40) of the tube, a notch (42; 44) located in the region of the free space (E) and s' extending over a selected length (L) in the axial direction of the tube, so that each tube end (38; 40) forms two distinct and aligned flat ends (46, 48; 50, 52). 2. flat tube according to claim 1, characterized in that the notch (42; 44) is rectangular in shape and has a width (1) of value substantially equal to the value of the free space (E) between the two folded longitudinal edges (26, 28). 3. flat tube according to one of claims 1 and 2, wherein each of the ends (38; 40) is adapted to be received in a collecting plate (56; 82) of a heat exchanger, characterized in that the axial length (L) of the notch (42; 44) is greater than the thickness (e) of the collector plate. 4. flat tube according to one of claims 1 to 3, characterized in that each of the folded edges (26, 28) has a generally L-shaped profile having an intermediate wing (30; 32) extending perpendicular to the large face (16) of the tube and a terminal wing (34; 36) applied flat against the large face (16). 5. Flat tube according to one of claims 1 to 4, characterized in that the metal sheet is made from an aluminum alloy and is coated with a solder plating. 6. Heat exchanger, characterized in that it comprises a row of flat tubes (10) according to one of claims 1 to 5, in which the ends (38; 40) of the tubes (10) are connected to two plates collectrIces (56; 82) respectively connected to two fluid boxes (58; 84). 7. Heat exchanger according to claim 6, characterized in that each of the collector plates (56; 82) comprises a row of double holes (60) equal in number to that of the tubes, each double hole being dimensioned to receive the two end pieces (46, 48; 50, 52) of one end (38; 40) of a flat tube (10). 8. Heat exchanger according to claim 7, characterized in that each double hole (60) is formed by two aligned oblong holes, separated from each other by a bridge of material (62) of width (P) substantially equal to the value of the free space (E) between the two folded longitudinal edges (26, 28) of a flat tube (10). 9. Heat exchanger according to one of claims 6 to 8, characterized in that the axial length (L) of the notch (42; 44) of each tube end is greater than the thickness (e) of the manifold plate (56; 82), so that, after assembly, the two end pieces (46, 48; 50, 52) of each tube protrude inside the fluid box. 10. Heat exchanger according to one of claims 6 to 9, characterized in that one of the fluid boxes includes a partition (72) which divides the interior of the fluid box (58) into two parallel compartments, namely an inlet compartment (78) communicating with first channels (14) of the tubes (10) and an outlet compartment (80) communicating with second channels (12) of the tubes, and in that the partition (72 ) has a longitudinal edge (74) received in the respective notches (42) of the ends (46, 48) of the tubes opening into the fluid box (58).