Heat exchanger for motor vehicle, comprising tubes with internal fins

Abstract

The invention proposes a heat exchanger for a motor vehicle, comprising a plurality of tubes 1 inside which a first fluid is able to circulate, each tube 1 being flat and provided with an internal fin 3 extending inside the tube 1 and being folded so as to form a crenellation composed of a succession of lateral partitions 3a and vertices 3b, said vertices 3b being in contact with the transverse walls 2a, 2b of the tube 1, said internal fin 3 defining a plurality of channels 4, each lateral partition 3a extending along the axis X and separating two adjacent channels 4. This exchanger is characterized in that said lateral partitions 3a are provided with means for increasing the heat transfer coefficient consisting of bosses 5. Figure for the abstract: Figure 1

Description

Title of the invention: Heat exchanger for a motor vehicle, comprising tubes with internal fins Technical field of the invention

[0001] 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 tubes.

[0002] The invention also relates to a method of manufacturing such a heat exchanger.

[0003] Such heat exchangers are in particular arranged on a loop of a cooling circuit, making it possible to dissipate calories. Technical background

[0004] 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.

[0005] Electric vehicles have electric pumps whose power is 10 to 20 times lower than the power of mechanical pumps in thermal vehicles, producing coolant flow rates which are low in the exchangers of electric vehicles.

[0006] Under these conditions, it is difficult to obtain good thermal performance.

[0007] A significant portion of heat exchangers produced for the needs of my Thermal management of motor vehicles is based on assembly technologies including flat tubes and fins.

[0008] There are three main tube technologies: bent tubes, electro-welded tubes and extruded tubes.

[0009] The internal fins are generally folded in an accordion shape inside the tubes, and create multiple flow channels for the first fluid.

[0010] Adding internal fins to the tubes increases the exchange surface area with the fluid. This compensates for the low exchange coefficients, also called heat transfer coefficients. As a reminder, the thermal power is proportional to the exchange coefficient multiplied by the exchange surface area.

[0011] These fins thus promote the dissipation of calories at the level of the heat exchanger thanks to their exchange surfaces which are added to the exchange surfaces of the walls forming the perimeter of the tube.

[0012] However, the exchange coefficient remains low since the flow of the fluid in the tube remains laminar.

[0013] To improve this exchange coefficient, it is possible to provide cutouts in the fins, in the form of louvers, in order to create additional obstacles on the path of the first fluid, to agitate it. However, these openings have a negative impact on the flow rate of the fluid, because the fluid tends to pass from one channel to another via the openings, in a zigzag, therefore with lateral deviations.

[0014] It is also possible to add bosses on the external walls of the tubes. The bosses are directed towards the inside of the channels. In this way, it is possible to create turbulence in the fluid circulating in the channels, which improves the exchange coefficient.

[0015] However, with the presence of an internal fin within the tube, the space available between two vertical walls of the fin is too small to allow a boss to be placed there. And even if the space were sufficient to put a boss there, there would only be one on one side for each channel because the other side is covered by the brazed contact area between the tube and the fin.

[0016] The present invention aims to improve these flat tubes provided with internal fins.

[0017] The objective of the present invention is to increase the exchange coefficient within the tube, without making it heavier, and without modifying its flat shape which is beneficial for its brazing with the internal fin. Summary of the invention

[0018] This object is achieved by means of a heat exchanger for a motor vehicle, comprising a plurality of tubes inside which a first fluid is capable of circulating in a flow direction with a longitudinal 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 axis Z, and two opposite lateral walls connecting the transverse walls, each tube being provided with an internal fin extending inside the tube and being folded so as to form a crenellation composed of a succession of lateral partitions and transversely oriented vertices, said vertices being in contact with the transverse walls of the tube, said internal fin defining a plurality of channels,each side partition extending along the X axis and separating two adjacent channels.

[0019] This exchanger is mainly characterized in that said side partitions are provided with means for increasing the heat transfer coefficient consisting of bosses.

[0020] The main idea of ​​this invention consists in providing the internal fin with bosses, in order to induce disturbances in the flow of the fluid within the tube, and a fortiori within all the channels of the tube.

[0021] The fluid flowing in each channel is then diverted from its straight path, because it must go around each bump it encounters. This agitation makes it possible to increase the exchange coefficient, and thus to increase the thermal performance of the tube and the exchanger more generally.

[0022] The bosses have the advantage of not inducing additional weight in the tube.

[0023] In addition, the fluid circulating in a channel will be disturbed within the channel itself, and will not will not be able to pass into another channel as in the prior art. Thus, the flow rate of the fluid within the channel remains constant.

[0024] Only the side walls of the internal fin are provided with the bosses, not the tops. Thus, all the tops can be properly brazed to the transverse walls of the tube, in order to ensure the long-term mechanical strength of the tube. The tops are generally flat.

[0025] According to the different embodiments of the invention, which may be taken together or separately: - each side partition has several bosses regularly repeated along the X axis. - each side partition has several bosses distributed over the height of the side partition along the Z axis, for the same abscissa on the X axis. - in each channel, the lateral partitions bordering it have bosses directed towards the inside of the channel, inducing a deviation of the fluid towards the transverse walls. - in each channel, for the same abscissa on the X axis, the lateral partitions bordering it have at least one pair of bosses facing each other and directed towards the inside of the channel. - in each channel, for the same abscissa on the X axis, the lateral partitions bordering it have a pair formed of a pair of upper bosses proximal to one of the transverse walls and a pair of lower bosses proximal to the other transverse wall. - the abscissas locating couples with each a pair of upper bosses and a pair of lower bosses are shifted from one channel to another. - each boss has a depth between 20% and 50% of the spacing between two adjacent side partitions along a Y axis perpendicular to the X and Z axes. - preferably each boss has a depth of 30% of the spacing between two adjacent side partitions along the Y axis. - each boss has a relief with an angular orientation of between 30° and 60° relative to the longitudinal axis of extension of the corresponding side partition.

[0026] The invention also relates to a method of manufacturing a heat exchanger, comprising at least one step of surface texturizing the lateral partitions of the internal fin by means of a wheel to form the raised bosses. Brief description of the figures

[0027] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0028] [Fig.l] is a sectional view of a tube with an internal fin provided with bosses according to a first configuration of the invention;

[0029] [Fig.2] shows three examples of boss shapes applied to the internal fin according to the first configuration;

[0030] [Fig. 3] is a sectional view of a tube with an internal fin provided with bosses according to a second configuration of the invention;

[0031] [Fig.4] is a side view of a section of an internal partition of a fin according to the second configuration;

[0032] [Fig.5] is an enlarged sectional view of the tube according to the second configuration;

[0033] [Fig.6] shows section BB of [Fig.5];

[0034] [Fig.7] shows the CC section of [Fig.5];

[0035] [Fig.8] illustrates the different stages of forming a tube with a fin internal according to the invention;

[0036] [Fig.9] shows the production of bosses in a sheet metal used to form a tube with an internal fin. Detailed description of the invention

[0037] In the remainder of the description, elements having an identical structure or similar functions will be designated by the same references.

[0038] 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" of the figures.

[0039] A heat exchanger comprises a stack along the Z axis of a plurality of tubes 1, each tube extending along the longitudinal axis X.

[0040] As can be seen in Figures 1 and 3, each tube 1 is provided with an internal fin 3 folded so as to delimit 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.

[0041] A space is provided between the tubes 1 so that a second fluid can circulate between the tubes 1 through the heat exchanger.

[0042] Figures 1 and 3 show a tube 1 according to the invention. This 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.

[0043] In addition to these different external walls 2a, 2b, 2c, 2d, the tube 1 has a plurality of internal partitions formed by an internal fin 3 which extends inside the tube 1.

[0044] In this case, the internal fin 3 is folded so as to form a crenellation composed of a succession of lateral partitions 3a and transversely oriented vertices 3b. The vertices 3b are generally flat.

[0045] Each lateral partition 3a extends from the lower transverse wall 2b to the upper transverse wall 2a, and vice versa.

[0046] In the example presented, these lateral partitions 3a are oriented vertically, that is to say parallel to the plane defined by the axes X and Z, so as to form a crenellation of rectangular section.

[0047] In the context of the present invention, these lateral partitions 3a could also be oriented obliquely, so as to form a crenellation which is not rectangular but of trapezoidal section.

[0048] Each vertex 3b is in contact with a transverse wall 2a, 2b.

[0049] Brazing is carried out between the vertices 3b and the transverse walls 2a, 2b to ensure continuity of material between the parts. This also contributes to the mechanical resistance of the assembly, in particular when the tube 1 is pressurized with the fluid inside.

[0050] Each lateral partition 3a separates two channels 4.

[0051] In the present case, there are nine lateral partitions 3a, making it possible to separate ten channels 4. It is possible to have more or fewer lateral partitions 3a in order to have more or fewer channels 4. At a minimum, there is one lateral partition 3a, so as to have at least two channels 4.

[0052] In order to improve the thermal performance of the tube 1, bosses 5 are made in the lateral partitions 3a of the fin 3 so as to disturb the flow of the fluid inside the channels 4. By disturbing the flow of the fluid, the heat exchange coefficient is increased and thus the general thermal performance of the exchanger is improved.

[0053] On each side partition 3a, these bosses 5 are repeated regularly along the X axis.

[0054] For each lateral partition 3a, it is possible to have one or more bosses 5 on the same abscissa of the X axis, that is to say several bosses 5 distributed over the height of the lateral partition 3a along the Z axis.

[0055] In [Fig. 1] for example, there are two bosses 5 on the height.

[0056] In Figure 2c, there are up to four bosses 5 distributed over the height.

[0057] The bosses 5 can take different geometric shapes in relief. The most common are illustrated in [Fig. 2]. We thus find the shape of oblong bosses 5 in figure 2a, and the shape of chevron bosses 5 in figures 2b, 2c.

[0058] The bosses 5 can have different orientations.

[0059] In Figure 2b, the bosses 5 are distributed into a lower group and an upper group with a slight offset in their abscissa so as to have bosses 5 in staggered rows.

[0060] In Figure 2c, the bosses 5 are also distributed into a lower group and an upper group, without offset in their abscissa. There are large bosses 5, and small bosses 5.

[0061] Thus the bosses 5 are distributed uniformly on each lateral partition 3a, both in height along the Z axis and longitudinally along the X axis.

[0062] According to a first possible configuration of the invention, illustrated in Figures 1 and 2, the bosses 5 are all formed on the same face of the lateral partitions 3a, that is to say on the same face of the internal fin 3 when it is unfolded.

[0063] Thus, in each channel 4, there are bosses 5 directed towards the inside of the channel 4 for the left partition 3a, and bosses 5 directed towards the outside of the channel 4 for the right partition 3a.

[0064] The fluid flowing in the channels 4 is disturbed and agitated by all these successive bosses 5. In this case, each time bosses 5 pass along the left partition, the fluid must move away from the left partition 3a, as illustrated by the arrows. And each time bosses 5 pass along the right partition, the fluid moves closer to the right partition 3a, as illustrated by the arrows. This causes small lateral movements of the fluid relative to the partitions 3a, causing agitation in the flow.

[0065] These bosses 5 make it possible to improve the heat transfer on the surfaces of the side partitions 3a, by a thermal conduction effect.

[0066] According to a second possible configuration of the invention, illustrated in Figures 3 to 7, the bosses 5 are formed on the two faces of each lateral partition 3a, that is to say on the two faces of the internal fin 3 when it is unfolded.

[0067] Thus in each channel 4, there are bosses 5 directed towards the inside of the channel 4 both on the left partition 3a and on the right partition 3a.

[0068] In [Fig.3], the bosses 5 formed on a first abscissa of the X axis, and in dotted lines the bosses 5 formed on a second abscissa of the X axis, to show that there are indeed bosses 5 oriented towards the inside of each channel 4.

[0069] The bosses 5 are configured so that the fluid circulating inside the channel 4 is diverted towards the transverse walls 2a, 2b of the tube 1. Thus at the level of the passage of bosses 5, a part of the fluid circulating at mid-height of the channel 4 will be directed towards the first transverse wall 2a and another part of the fluid circulating at mid-height of the channel 4 will be directed towards the second transverse wall 2b. This redirection is illustrated by the arrows extending from the bosses 5.

[0070] This deflection of the fluid towards the transverse walls 2a, 2b will make it possible to increase the heat transfer on the transverse walls 2a, 2b by direct contact or via the tops 3b of the fin 3 which are in contact with the transverse walls 2a, 2b.

[0071] For good deflection to take place, it is preferable that the depth P2 of each boss, along the Y axis, corresponds to 20% to 50% of the spacing PI between two adjacent lateral partitions 3a.

[0072] This type of boss 5 is deeper than those produced in the context of the first configuration of the invention.

[0073] To have a more powerful effect of this deviation, it is advantageous to arrange the bosses 5 directed towards the inside of the channel 4 opposite each other, so as to form pairs of bosses 5 which reduce the passage section of the fluid when the latter passes between the bosses 5 of the same pair. The passage section being reduced, to maintain a constant flow rate, the fluid is automatically diverted upwards and downwards, therefore towards the transverse walls 2a, 2b.

[0074] To further increase this deviation, it is advantageous to provide bosses 5 with a specific orientation in the plane defined by the X and Z axes.

[0075] As illustrated in [Fig.4], the boss 5 may be elongated, with a first end located at a first abscissa, and a second end located at a second abscissa further along the flow axis X. The direction of flow is illustrated by the large arrow. The first end is distal to the nearest transverse wall 2a, 2b, while the second end is proximal to the nearest transverse wall 2a, 2b.

[0076] This produces a boss 5 arranged obliquely on the lateral partition 3a, and showing the direction to be taken by the fluid so that it approaches the transverse wall 2a, 2b.

[0077] In other words, the boss 5 comprises a guideline having an angle α relative to the axis X of the fluid flow.

[0078] Preferably, this angle a is between 30° and 60°.

[0079] Indeed, this angle a must be sufficient to deflect the fluid towards the trans walls versales 2a, 2b, and this angle a must not be too large to avoid creating a stop on which the fluid would hit, which would create a large pressure drop.

[0080] In the example of [Fig.4], the boss 5 is oval in shape. However, any other elongated geometric shape falls within the scope of the present invention. For example, an oblong or chevron shape may be suitable.

[0081] In [Fig.3], the bosses 5 are arranged rather at mid-height of the partitions 3a, along the Z axis.

[0082] In Figures 5 to 7, another preferred example of arrangement of bosses 5 on the side partitions 3a of an internal fin 3 is illustrated.

[0083] The bosses 5 are referenced from A to H.

[0084] On each side partition 3a, there are bosses 5 in the upper part, that is to say proximal to the upper transverse wall 2a, and there are bosses 5 in the lower part, i.e. proximal to the lower transverse wall 2b.

[0085] In this example, the bosses 5 are located opposite each other, that is to say that there are always two bosses 5 directed towards the inside of the channel 4 and located opposite each other on the lateral partitions 3a which border the channel 4. This is a pair of bosses 5.

[0086] In a channel 4, for the same abscissa on the X axis, there are two bosses 5 facing each other in the upper part and two bosses 5 facing each other in the lower part. Therefore two pairs of bosses 5.

[0087] For example, in channel 4 on the left, for abscissa XI, there are the two bosses A and B in the upper part, and the two bosses E and F in the lower part. There is therefore a pair of pairs of bosses.

[0088] When the fluid arrives at the level of these four bosses 5, a part of the fluid, guided by bosses A and B, will be directed towards the upper transverse wall 2a, and the other part of the fluid, guided by bosses E and F, will be directed towards the top 3b in contact with the lower transverse wall 2b.

[0089] [Fig.6] shows the same bosses A and B when looking towards the upper transverse wall 2a.

[0090] [Fig.7] shows the same bosses E and F when looking towards the lower transverse wall 2b.

[0091] In channel 4 on the right, for the abscissa X2, there are the two bosses C and D in the upper part, and the two bosses G and H in the lower part. There is therefore another pair of boss pairs.

[0092] When the fluid arrives at the level of these four bosses 5, a part of the fluid, guided by bosses C and D, will be directed towards the upper transverse wall 2a, and the other part of the fluid, guided by bosses G and H, will be directed towards the top 3b in contact with the lower transverse wall 2b.

[0093] [Fig.6] shows the same bosses C and D when looking towards the wall upper transverse 2a.

[0094] [Fig.7] shows the same bosses G and H when looking towards the lower transverse wall 2b.

[0095] There is an abscissa shift between the pairs A, B and C, D located in the upper part in adjacent channels 4 because it is impossible to create a boss 5 which is at the same time directed towards the inside of the two adjacent channels 4. Indeed, the lateral partition 3a can only be deformed at a precise point towards one of the channels 4.

[0096] Hence the staggered position of the pairs A, B and C, D along the axis.

[0097] The same remark applies to the pairs E,F and G,H.

[0098] It is possible to provide bosses 5 with a depth P2 equal to 50% of the spacing PI between two adjacent lateral partitions 3a. In this case, the bosses 5 opposite each other touch. There is therefore no longer a simple reduction in passage, but a barrier that the fluid must avoid by going around it upwards and downwards, that is to say towards the transverse walls 2a, 2b.

[0099] The invention also relates to a method of manufacturing a heat exchanger from tubes 1 provided with internal fins 3 as described previously.

[0100] This method comprises a step of surface texturizing the lateral partitions 3a of the internal fin 3 by means of a wheel 8 to form the raised bosses 5.

[0101] This wheel 8 makes it possible to deform at least one face of the fin 3.

[0102] To deform the two faces of the fin 3, that is to say front and back, it is preferable to use two wheels 8 between which the fin 3 passes, as illustrated in [Fig.9].

[0103] Conventionally, the wheel 8 has reliefs which correspond to the counterforms of the bosses 5.

[0104] For example, the internal fin 3 may consist of a flat plate 7 made of a metallic material, on which the wheel 8 applies pressure so as to deform it to create the bosses 5. Then this embossed plate 7 is folded so as to create the crenellation, and a fin 3 is obtained. This embossed and folded fin 3 is then placed on another plate which will in turn be folded so as to form the external walls of the tube 1, all around the internal fin 3.

[0105] In another example, the internal fin 3 and the tube 1 are formed from the same plate 7, as illustrated in FIG. 8a.

[0106] The two lateral edges 6 are deformed using wheels 8 which apply pressure so as to create the bosses 5, on the front or on both sides.

[0107] Then these two embossed side edges 6 are folded so as to form a crenellation.

[0108] Then these two embossed and crenellated side edges 6 are folded towards the center of the plate 7 twice until they touch in the middle of plate 7, as shown in image 8b.

[0109] A flat tube 1 is then obtained inside which the internal fin 3 formed by the two embossed and folded lateral edges 6 extends.

[0110] The configurations shown in the cited figures 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

Claims

1. Heat exchanger for a motor vehicle, comprising a plurality of tubes (1) inside which a first fluid is capable of circulating in a flow direction with a longitudinal 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 lateral walls (2c, 2d) connecting the transverse walls (2a, 2b), each tube (1) being provided with an internal fin (3) extending inside the tube (1) and being folded so as to form a crenellation composed of a succession of lateral partitions (3a) and vertices (3b) oriented transversely, said vertices (3b) being in contact with the transverse walls (2a, 2b) of the tube (1),said internal fin (3) defining a plurality of channels (4), each lateral partition (3a) extending along the X axis and separating two adjacent channels (4), characterized in that said lateral partitions (3a) are provided with means for increasing the heat transfer coefficient consisting of bosses (5) and in that in each channel (4), for the same abscissa on the X axis, the lateral partitions (3a) bordering it have at least one pair of bosses (5) facing each other and directed towards the inside of the channel (4).,

2. Heat exchanger according to the preceding claim, characterized in that each lateral partition (3a) comprises several bosses (5) regularly repeated along the X axis.

3. Heat exchanger according to one of the preceding claims, characterized in that each lateral partition (3a) comprises several bosses (5) distributed over the height of the lateral partition (3a) along the Z axis, for the same abscissa on the X axis.

4. Heat exchanger according to one of the preceding claims, characterized in that, in each channel (4), the lateral partitions (3a) bordering it have bosses (5) directed towards the inside of the channel (4), inducing a deviation of the fluid in the direction of the transverse walls (2a, 2b).

5. Heat exchanger according to claim 1, characterized in that, in each channel (4), for the same abscissa on the X axis, the partitions lateral (3a) bordering it have a pair formed of a pair of upper bosses (5) proximal to one of the transverse walls (2a, 2b) and a pair of lower bosses (5) proximal to the other transverse wall (2b, 2a).

6. Heat exchanger according to the preceding claim, characterized in that the abscissas locating pairs each with a pair of upper bosses (5) and a pair of lower bosses (5) are offset from one channel (4) to the other.

7. Heat exchanger according to one of the preceding claims, characterized in that each boss (5) has a depth P2 of between 20% and 50% of the spacing PI between two adjacent lateral partitions (3a) along an axis Y perpendicular to the axes X and Z.

8. Heat exchanger according to one of the preceding claims, characterized in that each boss (5) has a relief with an angular orientation of between 30° and 60° relative to the longitudinal axis of extension of the corresponding lateral partition (3a).

9. Method of manufacturing a heat exchanger according to one of the preceding claims, comprising at least one step of surface texturizing the lateral partitions (3a) of the internal fin (3) by means of a wheel (8) to form the raised bosses (5).

Images