WO2024200407A1 - Heat exchanger for a motor vehicle, comprising extruded tubes - Google Patents

Abstract

The invention proposes a heat exchanger for a motor vehicle, which heat exchanger comprises a plurality of extruded tubes (1), each tube (1) having two opposite transverse walls (2a, 2b), and two opposite side walls (2c, 2d) connecting the transverse walls (2a, 2b), each tube (1) comprising a plurality of channels (5) in which the first fluid flows, the channels (5) being separated by complete internal partitions (3) parallel to the side walls (2c, 2d), characterised in that, in each channel (5), the tube (1) has at least one partial internal partition (4), parallel to the complete internal partitions (3), and extending from one of the transverse walls (2a, 2b), the other transverse wall (2b, 2a) located facing the partial internal partition (4) having at least one primary boss (6) directed towards the inside of the channel (5) and coming into contact with the partial internal partition (4).

Description

Heat exchanger for motor vehicle, comprising extruded tubes

Technical field of the invention

The field of the present invention is that of heat exchangers, in particular for motor vehicles, and it relates more particularly to heat exchangers comprising a bundle of extruded tubes.

The invention also relates to a method of manufacturing such a heat exchanger.

Such heat exchangers are notably arranged on a loop of a cooling circuit, allowing calories to be dissipated.

Technical background

In a known manner, a heat exchanger for a motor vehicle comprises a plurality of tubes extending parallel to each other and in which a first fluid present in the cooling circuit loop can circulate. The heat exchanger is configured to allow an exchange of calories between a second fluid passing around the tubes and the first fluid circulating inside the tubes.

A significant portion of heat exchangers produced for the thermal management needs of automotive vehicles are based on assembly technologies comprising tubes and fins. There are three main tube technologies: bent tubes, electro-welded tubes and extruded tubes.

This last category is of particular interest for electric vehicles. The latter have electric pumps whose power is 10 to 20 times lower than the power of mechanical pumps in thermal vehicles, inducing coolant flow rates that are low in electric vehicle exchangers.

Therefore, it is difficult to achieve good thermal performance.

Extruded tube technology, which increases the available exchange surface thanks to additional internal partitions, makes it possible to compensate for the low exchange coefficients. As a reminder, the thermal power is proportional to the exchange coefficient multiplied by the exchange surface. These extradited tubes thus promote the dissipation of calories at the level of the heat exchanger thanks to the increase in exchange surfaces.

To further improve the thermal performance of the extruded tubes, it is possible to add bosses to the external walls, similar to what is done in folded tubes. The bosses are directed towards the inside of the channels. In this way, it is possible to create turbulence in the cooling fluid circulating in the channels, which improves the heat exchange.

One of the important locks then lies in the fact that a boss must be framed by two vertical internal partitions. In this way, the pressure applied during the stamping of the boss does not deform the entire width of the tube. The boss can also straddle one or more vertical internal partitions but in this case, its production causes the deformation of the underlying partitions.

This produces multi-channel tubes thanks to the additional internal partitions, and provided with bosses on the external walls of the tube.

This embodiment of a multi-channel extruded tube provided with bosses has the following disadvantages:

-The number of internal partitions required is significant, which penalizes the weight of the component,

-The fluid channels are isolated from each other, which limits the thermal performance of the assembly (because the more fluid mixing, the higher the performance).

The present invention aims to improve these extruded tubes.

The objective of the present invention is to increase turbulence and mixing in the fluid flow in an extruded tube, while limiting the weight of the tube, and without deforming the internal partitions.

Summary of the invention

This aim is achieved by means of a heat exchanger for a motor vehicle, comprising a plurality of extruded tubes inside which a first fluid is capable of circulating in a flow direction of axis X, the tubes being stacked along an axis Z perpendicular to the axis X, a space being provided between two successive tubes and allowing the passage of a second fluid. promoting heat exchange with the first fluid, each tube being flat and having two opposite transverse walls each extending in a plane perpendicular to the Z axis, and two opposite side walls connecting the transverse walls, each tube comprising a plurality of channels in which the first fluid flows, said channels being separated by complete internal partitions parallel to the side walls.

This exchanger is mainly characterized in that, in each channel, the tube has at least one partial internal partition, parallel to the complete internal partitions, and extending from one of said transverse walls, the other transverse wall located opposite the partial internal partition having at least one primary boss directed towards the inside of the channel and coming into contact with the partial internal partition.

The main idea of this invention is to replace traditional complete internal partitions with partial internal partitions, i.e. not extending over the entire height of the tube.

More precisely, a complete internal partition extends over the entire height of the tube, therefore along the Z axis, from one transverse wall to the opposite transverse wall, and this over the entire length of the tube.

A partial internal partition extends over only part of the height of the tube, i.e. from a transverse wall, without reaching the opposite transverse wall, and this over the entire length of the tube.

The internal partitions necessarily extend over the entire length of the tube, because the tube is extruded.

The presence of partial internal partitions instead of complete internal partitions allows to reduce the weight of the tube and save raw material.

The primary boss deforms the outer cross wall of the tube until it comes into contact with the free edge of the partial internal partition below. Thus, only the cross wall is deformed, and the partial internal partition is never deformed.

Each channel is delimited by two adjacent complete internal partitions, or by a complete internal partition and a side wall. Within each channel extends a partial internal wall.

This partial internal wall thus divides the channel into three zones, namely two sub-channels on either side of the partial internal wall, and a zone of mixture in the remaining space between the free edge of the partial partition and the opposite transverse wall.

At a primary boss, the mixing zone no longer exists and there are only the two sub-channels in which the first fluid is distributed. Downstream of the primary boss, the mixing zone is re-established, and the first fluid can mix again.

Thus, the first fluid flowing into the channels is disturbed at each passage of a primary boss, which it must bypass on the right and on the left, taking the sub-channels. The fluid remixes in the channel after each passage of a primary boss.

These disturbances with these additional mixtures make it possible to considerably increase the heat exchange coefficient, and therefore the thermal performance of the exchanger.

According to the different embodiments of the invention, which may be taken together or separately: the partial internal partition extends alternately, from one of said transverse walls in a channel, and from the other transverse wall in an adjacent channel: this alternation in the channels makes it possible to alternately deform one or the other transverse wall, in order to balance the forces exerted on the tube at the time of driving to create the primary bosses.

- each partial internal partition is located in the middle of the channel: thus the partial internal partition divides the channel into two sub-channels of identical section.

- the primary boss is centered in relation to the partial internal partition: the low point of the boss is then the one which comes into contact with the free edge of the partial internal partition.

- the transverse wall located opposite the partial internal partition is brazed to the partial internal partition at the primary boss: brazing is used to recreate a continuity of material between the transverse walls and the partial internal partitions. This continuity of material contributes to the mechanical strength of the tube, and prevents the walls surrounding each channel from swelling when the fluid is injected inside. said partial internal partition extends over a Z axis height of between 60% and 80% of the height of the channel. each primary boss extends over a Z axis height between 20% and 40% of the channel height.

- for each partial internal partition, primary bosses are regularly distributed on the opposite transverse wall along the X axis.

- secondary bosses are provided in the transverse walls, between a complete internal partition and a partial internal partition, and directed towards the inside of the channel.

The invention also relates to a method of manufacturing a heat exchanger, comprising at least one step of surface texturing of the transverse walls of the extruded tube by means of a wheel to form the primary raised bosses.

Advantageously, said wheel forms secondary raised bosses during the texturing step.

Brief description of the figures

Other features and advantages of the invention will become apparent upon reading the detailed description which follows, for the understanding of which reference will be made to the appended drawings in which:

Figure 1 is a sectional view of an extruded tube according to the prior art;

Figure 2 is a sectional view of an extruded tube according to the invention, before the formation of bosses, or outside the sections containing bosses;

Figure 3 is a sectional and perspective view of an extruded tube according to Figure 2;

Figure 4 is a sectional view of an extruded tube according to the invention, in a section containing primary bosses;

Figure 5 is a sectional and perspective view of an extruded tube according to Figure 4;

Figure 6 is a sectional view of an extruded tube according to the invention, in a section containing primary bosses and secondary bosses;

Figure 7 is a sectional and perspective view of an extruded tube according to Figure 6;

Figure 8 is a top view and in transparency, of a section of an extruded tube according to the invention after the formation of the primary and secondary bosses, and with a sectional view of the tube along AA for the correspondence of the channels. Detailed description of the invention

In the remainder of the description, elements having an identical structure or similar functions will be designated by the same references.

In the remainder of the description, we will adopt in a non-limiting manner - and without reference to Earth's gravity - longitudinal X, vertical Z and transverse Y orientations indicated by the trihedron "X,Z,Y" in the figures.

A heat exchanger comprises a stack along the Z axis of a plurality of tubes 1, each tube extending along the longitudinal axis X. These tubes 1 are extruded and have a plurality of channels 5 inside which a first fluid circulates in a flow direction X, therefore corresponding to the longitudinal axis of the tube 1.

A space is provided between the tubes 1 so that a second fluid can circulate between the tubes 1 through the heat exchanger.

Figure 1 shows a tube 1 extruded according to the prior art. This extruded tube 1 is flat, and has an upper transverse wall 2a and a lower transverse wall 2b. These two transverse walls 2a, 2b are parallel and connected by a right side wall 2d and a left side wall 2c. All these walls 2a, 2b, 2c, 2d are external, that is to say they form the periphery of the tube 1.

In addition to these different external walls 2a, 2b, 2c, 2d, the extruded tube 1 has a plurality of internal partitions 3 which are complete, that is to say which extend from the lower transverse wall 2b to the upper transverse wall 2a. These complete internal partitions 3 are oriented vertically, that is to say parallel to the plane defined by the axes X and Z. Each complete internal partition 3 separates two channels 5.

In this case, there are six complete internal partitions 3, making it possible to separate seven channels 5. I t is possible to have more than six complete internal partitions in order to have even more channels 5. At a minimum, there is one complete internal partition, so as to have at least two channels 5.

In order to improve the thermal performance of the tube, it is known to deform the transverse walls 2a, 2b of the tube 1 by bosses directed towards the inside of the channels 5 so as to disturb the flow of the fluid inside the channels 5. By disturbing the flow of the fluid, the coefficient heat exchange and thus improves the overall thermal performance of the exchanger.

In Figure 1, the areas where a boss is to be formed are illustrated in dotted lines. For example, the boss may be centered relative to a channel 5, and of small size. For example again, the boss may be centered relative to a complete internal partition 3, and of large size so as to cover two channels 5.

The bosses can take any geometric shape. Preferably, they consist of circles, chevrons, or oblongs.

The boss areas are shown on the upper cross wall 2a, but the bosses can be formed in the same way on the lower cross wall 2b.

The deformation of the transverse walls 2a, 2b also causes the deformation of the adjacent complete internal partitions 3. However, these deformations of the complete internal partitions 3 cause long-term mechanical resistance problems in the tube, as well as pressure loss problems.

Figures 2 and 3 show a tube 1 extruded according to the invention.

As with the tube 1 of the prior art, the extruded tube 1 of the invention has an upper transverse wall 2a and a lower transverse wall 2b. These two transverse walls 2a, 2b are connected by a right side wall 2d and a left side wall 2c. All of these walls 2a, 2b, 2c, 2d are external, i.e. they form the perimeter of the tube 1.

In addition to these different external walls 2a, 2b, 2c, 2d, the extruded tube 1 has a plurality of internal partitions 3 which are complete, that is to say which extend from the lower transverse wall 2b to the upper transverse wall 2a. These complete internal partitions 3 are oriented vertically, that is to say parallel to the plane defined by the axes X and Z.

Each complete internal partition 3 separates two channels 5.

In this case, there are three complete internal partitions 3, making it possible to separate four channels 5. It is possible to have more or fewer complete internal partitions 3, as desired.

The extruded tube 1 also has a plurality of internal partitions 4 which are partial, that is to say which extend from one of the transverse walls 2a, 2b, without reaching the opposite transverse wall 2b, 2a. These partial internal partitions 4 are also oriented vertically, that is to say parallel to the plane defined by the X and Z axes.

Each partial internal partition 4 extends over a height H1 of axis Z between 60% and 80% of the height H2 of channel 5.

In the present case, there is a partial internal partition 4 between two successive complete internal partitions 3. This results in an alternation between the complete internal partitions 3 and the partial internal partitions 4, along the width of the tube 1, i.e. along the Y axis.

In this example, the partial internal partition 4 is located in the middle of the channel 5. Thus, each partial internal partition 4 divides the channel 5 into two equal sub-channels Z1, Z2. The sub-channels Z1, Z2 are located on either side of the partial internal partition 4. Between the two sub-channels Z1, Z2 and the transverse wall 2a, 2b opposite the partial internal partition 4, there is a mixing zone Z3.

Thus, the first fluid circulating inside a channel 5, is divided and is located either in the first sub-channel Z1, or in the second sub-channel Z2, or in the mixing zone Z3.

In another example not shown, it would be possible to provide two partial internal partitions 4 in each channel 5. Thus, three sub-channels would be obtained, and a mixing zone Z3.

The partial internal partitions 4 therefore make it possible to divide the channels 5 into several zones in which the first fluid circulates.

In the example presented, there are 8 sub-channels Z1, Z2. We thus find at least as many sub-channels Z1, Z2 as there are channels 5 in the prior art, therefore at least as many heat exchanges.

With such partial internal partitions 4, there is a real saving of material which is achieved, and this allows in particular to lighten the weight of the tube, which is important for these heat exchangers embedded in vehicles.

Advantageously, a partial internal partition 4 extends from the lower transverse wall 2b into the channel 5 located on the far left, then a partial internal partition 4 extends from the upper transverse wall 2a into the adjacent channel 5 to the right, then a partial internal partition 4 extends from the lower transverse wall 2b into the still adjacent channel 5 to the right, then a partial internal partition 4 extends from the upper transverse wall 2a into the adjacent channel 5 located on the far right. There is thus an alternation in the arrangement of the partial internal partitions 4, from one channel 5 to the other, from one of the transverse walls 2a, 2b, then the other transverse wall 2b, 2a of the tube 1. This alternation is important to balance the weight, and also the forces which will be applied to the transverse walls 2a, 2b as we will see in the rest of the description.

In this case, in Figures 4 and 5, primary bosses 6 are made in the transverse walls 2a, 2b of the tube 1. These primary bosses 6 are directed towards the inside of the tube 1.

Each primary boss 6 is located opposite a partial internal partition 4, and comes into contact with the upper edge of the partial internal partition 4. Thus the low point of the primary boss 6 is against the partial internal partition 4 located opposite. In the present case, each primary boss 6 is centered relative to the corresponding partial internal partition 4.

Each primary boss 6 consists of a depression of material directed towards the inside of the tube 1.

Each primary boss 6 extends over a Z axis height of between 20% and 40% of the height H2 of the channel 5. This height depends on the height of the partial partition 4.

The depth P of a primary boss 6 is calculated so that it corresponds to the distance between the upper edge of the partial internal partition 4 and the opposite transverse wall 2a, 2b. Thus, when the boss is formed, there is contact between the deformed opposite transverse wall and the upper edge of the partial internal partition 4, and this without deformation of the partial internal partition 4. There is also no deformation of the complete internal partitions 3. The absence of deformation of these internal partitions 3, 4 makes it possible to ensure high mechanical strength of the tube 1.

After the formation of the primary bosses 6, brazing is carried out, in a conventional manner, to ensure continuity of material between the transverse walls 2a, 2b and the partial internal partitions 4. This also contributes to the mechanical resistance of the assembly, in particular when the tubes 1 are put under pressure with the fluid inside.

It can be seen that there is an alternation of primary boss 6 along the Y axis, between the upper transverse wall 2a and the lower transverse wall 2b. This alternation of primary boss 6 is due to the alternation of the partial internal partitions 4 which extend once from the upper transverse wall 2a and the other time from the lower transverse wall 2b. This alternation of the primary bosses 6 makes it possible to balance the deformations made on the tube 1, while ensuring at least one primary boss 6 per channel 5.

Preferably, the primary bosses 6 are made on the same section, that is to say on the same abscissa of the X axis, for all the channels 5.

It could be considered to produce primary bosses 6 offset along the X axis from one channel 5 to the other.

Advantageously, the primary bosses 6 are repeated along the X axis, and are therefore regularly distributed on the transverse walls 2a, 2b along the X axis.

At the location of the primary boss 6, there is no longer a mixing zone Z3, but the two sub-channels Z1, Z2 remain. Thus, the first fluid, which circulated in the mixing zone Z3 upstream of the primary boss 6, is distributed in the two sub-channels Z1, Z2 to bypass the primary boss 6. After passing the primary boss 6, the mixing zone Z3 is again present, as illustrated in FIG. 2, and the first fluid which leaves the two sub-channels Z1, Z2 is distributed again in the three zones Z1, Z2, Z3, namely the first sub-channel Z1, the second sub-channel Z2, and the mixing zone Z3. Thus, the first fluid continues to be disturbed and remixed at each passage of the primary boss 6, which makes it possible to considerably increase the heat exchange coefficient.

In addition to the primary bosses 6, the tube 1 may include secondary bosses 7 as illustrated in FIGS. 6 to 8.

These secondary bosses 7 are made on the transverse walls 2a, 2b of the tube 1.

Each secondary boss 7 is made between a partial internal partition 4 and a complete internal partition 3, or between a partial internal partition 4 and an external side wall 2c, 2d at the lateral ends of the tube 1.

The secondary bosses 7 consist of material depressions towards the inside of the tube 1.

Each secondary boss 7 is centered relative to a subchannel Z1, Z2. There are therefore two secondary bosses 7 per channel 5.

For each channel 5, when a primary boss 6 is made on one of the transverse walls 2a, 2b, two secondary bosses 7 are made on the opposite transverse wall 2b, 2a. As with the primary bosses 6, the secondary bosses 7 are repeated along the X axis, and are therefore regularly distributed on the transverse walls 2a, 2b.

Each secondary boss 7 has a dimension smaller than the dimension of a primary boss 6.

Indeed, each secondary boss 7 is intended to be formed in a sub-channel Z1, Z2. However, the width of a sub-channel Z1, Z2 is much less than the width of a channel 5.

There are therefore two secondary bosses 7 side by side, formed in two adjacent sub-channels Z1, Z2 of the same channel 5.

Thus, along the Y axis, on each transverse wall 2a, 2b, we successively find a primary boss 6 and two secondary bosses 7.

The secondary bosses 7 have a relatively low depth so that there is no deformation of the internal partitions located on either side.

The presence of these secondary bosses 7 reduces the passage section of the first fluid in the channel, and forces the first fluid to make waves, which has the effect of further disturbing the fluid in the sub-channels Z1, Z2 at the time of passage of the primary boss 6, and therefore of further improving the mixing which takes place inside the channel 5 throughout the flow.

Indeed, the advantage of this architecture is that it allows, via the primary bosses 6 and secondary bosses 7, significant mixing of the first fluid in the channels 5.

There is an offset d in the abscissa X between the primary bosses 6 and secondary bosses 7 made in the upper transverse wall 2a, and the primary bosses 6' and secondary bosses 7' made in the lower transverse wall 2b, as illustrated in Figure 8, by transparency. In this Figure 8, the bosses 6, 7 of the upper transverse wall 2a are illustrated in thick lines, and the bosses 6', 7' of the lower transverse wall 2b in thin lines. The partitions 4, 3 are represented by dashes.

For their formations, the secondary bosses 7, 7' in fact require that the partial partition 4 be held by the primary boss 6, 6' located opposite, from a mechanical resistance point of view during deformations. The primary boss 6, 6' must therefore be formed upstream of the secondary bosses 7, 7' (roll forming). The recommended X offset is between 50% and 100% of a primary pattern, knowing that this offset is understood as the distance in X separating the start of the primary boss and the start of the secondary boss.

The invention also relates to a method of manufacturing a heat exchanger from extruded tubes 1 comprising complete 3 and partial 4 internal partitions as described above.

This method comprises a first step which consists in producing a first series of primary bosses 6, of large size, on the upper 2a and lower 2b transverse walls of the tube 1, in line with the partial internal partitions 4. For this step, the complete internal partitions 3 defining the channel 5 allow the production of the primary bosses 6 without deformation of the rest of the tube 1. The depth of the primary bosses 6 is adjusted to guarantee contact with the partial internal partitions 4 once the depression has been carried out.

This first step is carried out using a stamping wheel.

At the end of this first stage, the contacts between the primary bosses 6 and the partial internal partitions 4 constitute additional support pillars in the middle of the channel 5.

It is then possible to move on to the second step which consists of making secondary bosses 7, of small size, in the sub-channels 5, opposite the primary bosses 6. This step is not possible without making the primary bosses 6.

The first and second steps are performed using the same stamping wheel.

There are thus at least two stamping wheels, one for each cross wall of the tube.

To ensure the successive production of the primary bosses 6 and secondary bosses on the two transverse walls 2a, 2b, it is necessary to have a position offset between the two rollers so that the secondary bosses 7 of the upper transverse wall are slightly offset relative to the primary bosses 6 of the lower transverse wall, and vice versa. This is clearly illustrated in FIG. 8. Thus, during the passage of the rollers, as soon as a primary boss 6' is stamped on the lower transverse wall 2b, secondary bosses 7 opposite with a slight offset d in X are then stamped on the upper transverse wall 2a. And as soon as a primary boss 6 is stamped on the upper transverse wall 2a, secondary bosses 7 facing each other with a slight offset in X are then stamped on the lower transverse wall 2b.

Among the possible boss shapes for the primary and secondary bosses, the preferred embodiment is limited to the use of bosses of round, oblong, chevron shape, or any combination of these shapes.

The configurations shown in the figures cited are only possible examples, in no way limiting, of the invention which on the contrary encompasses the variants of shapes and designs within the reach of those skilled in the art.

Claims

1 . Heat exchanger for a motor vehicle, comprising a plurality of extruded tubes (1) inside which a first fluid is capable of circulating in a flow direction of axis X, the tubes (1) being stacked along an axis Z perpendicular to the axis X, a space being provided between two successive tubes (1) and allowing the passage of a second fluid promoting heat exchange with the first fluid, each tube (1) being flat and having two opposite transverse walls (2a, 2b) each extending in a plane perpendicular to the axis Z, and two opposite side walls (2c, 2d) connecting the transverse walls (2a, 2b), each tube (1) comprising a plurality of channels (5) in which the first fluid flows, said channels (5) being separated by complete internal partitions (3) and parallel to the side walls (2c, 2d), characterized in that, in each channel (5), the tube (1) has at least one partial internal partition (4), parallel to the complete internal partitions (3), and extending from one of said transverse walls (2a, 2b), the other transverse wall (2b, 2a) located opposite the partial internal partition (4) having at least one primary boss (6) directed towards the inside of the channel (5) and coming into contact with the partial internal partition (4). 2. Heat exchanger according to the preceding claim, characterized in that the partial internal partition (4) extends alternately, from one of said transverse walls (2a, 2b) in a channel (5), and from the other transverse wall (2b, 2a) in an adjacent channel (5). 3. Heat exchanger according to one of the preceding claims, characterized in that each partial internal partition (4) is located in the middle of the channel (5). 4. Heat exchanger according to one of the preceding claims, characterized in that the primary boss (6) is centered relative to the partial internal partition (4). 5. Heat exchanger according to one of the preceding claims, characterized in that the transverse wall (2a, 2b) located opposite the partial internal partition (4) is brazed to the partial internal partition (4) at the level of the primary boss (6). 6. Heat exchanger according to one of the preceding claims, characterized in that said partial internal partition (4) extends over a height of axis Z of between 60% and 80% of the height of the channel (5). 7. Heat exchanger according to one of the preceding claims, characterized in that, for each partial internal partition (4), primary bosses (6) are regularly distributed on the opposite transverse wall (2a, 2b) along the X axis. 8. Heat exchanger according to one of the preceding claims, characterized in that secondary bosses (7) are provided in the transverse walls (2a, 2b), between a complete internal partition (3) and a partial internal partition (4), and directed towards the inside of the channel (5). 9. A method of manufacturing a heat exchanger according to claim 1, comprising at least one step of surface texturing of the transverse walls (2a, 2b) of the tube (1) by means of a wheel to form the primary raised bosses (6). 10. Method according to the preceding claim, characterized in that said wheel forms secondary bosses (7) in relief during the texturing step.