WO2008053092A1 - Heat exchanger with central channel for a heat exchange fluid - Google Patents

Abstract

The invention relates to a heat exchanger, comprising a body (3) defining a central channel (7), surrounded by peripheral channels (10) and having ends provided with means for defining independent circuits arranged such that the central channel permits the circulation of a heat exchange fluid and the peripheral channels permit the circulation of a fluid for thermal treatment.

Description

Central channel heat exchanger for heat transfer fluid

The present invention relates to fluid transport circuits such as those used in motor vehicles, in particular to recirculate the exhaust gases of the combustion engines of these vehicles.

BACKGROUND OF THE INVENTION An exhaust gas recirculation circuit of the engine of a motor vehicle (commonly called EGR for "Exhaust Gas Recirculation") extends between the exhaust circuit and the intake circuit of the engine. thermal engine and conventionally comprises a heat exchanger for cooling the exhaust gas, an uncooled bypass channel, a bypass valve for selectively directing the gas flow into the heat exchanger or the bypass duct, and a valve regulator for regulating the flow rate of the gas stream in the recirculation circuit.

The heat exchanger comprises a body comprising tubes received in an outer casing whose ends are connected to flanges for connection to the circuit. Such an exchanger comprises a large number of brazed parts to each other.

There are also exchangers whose body comprises an outer casing having ends provided with connecting flanges and receiving two half-shells molded and contiguous, provided with internally-spaced fins to facilitate heat exchange between, on the one hand, the fluid to cool circulating between the fins and, on the other hand, the heat transfer fluid flowing between the outer shell and the half-shells. There are other molded structures with an overlay channels alternately assigned to transport the fluid to be cooled and the coolant.

One of the critical points in the manufacture of these exchangers is the realization of one seal, particularly at the ends of the body of the exchanger, to prevent leakage of the coolant. However, in all these heat exchanger structures, the coolant extends around the gas flow channels. The areas to be sealed are important, which increases the risk of leakage.

OBJECT OF THE INVENTION

An object of the invention is to provide a means for solving the aforementioned drawback.

SUMMARY OF THE INVENTION For this purpose, provision is made, according to the invention, for a heat exchanger comprising a body delimiting a first channel surrounded by peripheral channels, the exchanger being provided with independent circuit defining members arranged in such a way that the first channel allows the circulation of a coolant and the peripheral channels allow the circulation of a fluid to be heat treated.

The presence of a single heat transfer fluid channel makes it possible to have lengths to be sealed which are relatively limited. The risk of leakage of the coolant is reduced in this way. In addition, a central arrangement of the heat transfer fluid channel allows a significant proximity thereto of the peripheral fluid transport channels to be cooled, promoting the heat exchange between the fluid to be cooled and the heat transfer fluid.

Other features and advantages of the invention will emerge on reading the following description of particular non-limiting embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

Reference will be made to the appended drawings, among which:

FIG. 1 is a perspective view of a heat exchanger associated with a valve assembly according to the invention,

FIG. 2 is a view of this heat exchanger in section along the plane II of FIG. 1, the flap being in the position of connection of the valve assembly with the exchanger,

FIG. 3 is a partial view, similar to that of FIG. 2, showing the valve assembly when the flap is in a bypass position,

FIG. 4 is a fragmentary perspective view of the heat exchanger equipped with the valve assembly according to the invention,

FIG. 5 is a partial perspective view of the body of the heat exchanger,

FIG. 6 is an end view of the body of the heat exchanger according to a first embodiment,

FIG. 7 is a view similar to FIG. 6 of the body of the heat exchanger according to a second embodiment, FIG. 8 is a view similar to that of FIG. 6 of the body of the heat exchanger in accordance with FIG. third embodiment,

FIG. 9 is a view similar to that of FIG. 6 of a heat exchanger according to a fourth embodiment,

FIG. 10 is a view similar to that of FIG. 2, of the heat exchanger according to the fourth embodiment, FIG. 11 is a partial cutaway view of the body of a heat exchanger with a particular profile of the channel separation partition,

- Figure 12 is a view similar to that of Figure 6 of a body of heat exchanger ¹ according to a fifth embodiment,

- Figures 13 and 14 are end views of the body of the exchanger according to alternative embodiments, before assembly. DETAILED DESCRIPTION OF THE INVENTION

The invention is here described in application to a recirculation circuit of the exhaust gas of a motor vehicle engine.

In a manner known per se, the recirculation circuit is provided with means of its connection on the one hand to the exhaust circuit of the engine and on the other hand to the intake circuit of the engine. The operating principle of such a recirculation circuit is known in itself and will not be detailed below. Referring to Figures 1 to 6, the exhaust gas recirculation circuit comprises a heat exchange device comprising a heat exchanger, generally designated 1, associated with a valve assembly, generally designated 2. The heat exchanger 1 comprises a body generally designated 3 having an outer shell 4 of tubular shape having open ends 4.1, 4.2. The outer casing 4 has a parallelepipedic shape here and comprises walls 4.3, 4.4, 4.5 and 4.6 which are parallel and opposite two by two.

In the outer casing 4, two central partitions 5 extend parallel to each other and to a longitudinal axis 6 of the outer casing 4. The central partitions 5 have opposite longitudinal edges connected to the walls 4.3, 4.4 so as to define with these a central channel 7. The central channel 7 comprises enlarged portions 7.1, 7.2 in the vicinity of the walls 4.3, 4.4 so that the central channel 7 has a cross-section here in the form of I. The portions 7.1, 7.2 communicate with each other. outside the outer casing 4 by openings 8.1, 8.2 formed respectively in the walls 4.3, 4.4 in the vicinity of the ends 4.1, 4.2 of the outer casing 4.

In the outer casing 4, peripheral partitions 9 extend parallel to each other and to the longitudinal axis 6. The peripheral partitions 9 extend on either side of the central channel 7 and have edges opposed longitudinal walls respectively connected to the walls 4.5, 4.6 and central partitions 5 so as to define therewith peripheral channels 10. The peripheral channels 10 here have a rectangular cross section.

The central channel 7 has a section greater than that of the peripheral channels 10. The body 3 is made of aluminum by extrusion so that at the outlet of the extruder, the channels 7 and 10 have open ends. Extrusion manufacturing makes it possible to obtain a one-piece body, which limits assembly operations and minimizes manufacturing costs. The body 3 may also be made of a metal other than aluminum and more generally any material having sufficient thermal conduction properties.

On the ends 4.1, 4.2 of the outer envelope 4 are fixed independent fluid circuit defining members.

These members comprise two closure elements 11, 12 fixed by welding at the ends of the central channel 7, respectively on the end-end 4.1 and end-4.2 side of the outer casing 4. These members also comprise a return element 13 which has the shape of a cap having a cylindrical segment bottom wall with an axis perpendicular to the walls 4.5, 4.6 and which is fixed on the end 4.2 of the casing 4. L return element 13 makes it possible to send back a stream coming from some of the peripheral channels 10, in this case those identified 10. As it extends in the upper half of the outer envelope 4, towards the other peripheral channels 10, it is i.e. those identified 10. bs' extending into the lower half of the outer shell 4 (see more particularly Figures 5 and 6).

These members further include a connecting member of the ends of the peripheral channels 10, located on the end-end side 4.1, to fluid supply and discharge conduits. This connecting element is here formed by the valve assembly 2.

The valve assembly 2 comprises a valve body 21 having an end portion arranged to form a manifold 22 and an end portion 23 delimiting a first conduit 24 opening into the manifold 22 by a seat 25 for a valve 26 mounted movable in the manifold 22 between an extreme position of closure and an extreme open position of the first conduit 24. The end portion 23 is provided with means for connecting the first conduit 24 to an external pipe. The collector 22 extends the first conduit 24 and here forms a flared end thereof. The valve 26 is connected to the rod of an actuator 27 mounted outside the valve body 21 on the side of its end portion 23. The actuator 27, known per se, is arranged to slide in such a way that adjustable valve 26 between its two positions.

The collector 22 also defines a second conduit 28 opening into the collector 22 on the side of the wall 4.3 and perpendicular to the longitudinal axis 6. The second duct 28 is an inlet duct of a gas stream in the valve assembly 2 and the first duct 24 is an outlet duct of the gas stream of the assembly Valve 2. The second conduit 28 is thus intended to be connected to the exhaust system of the engine and the first conduit 24 is intended to be connected to the intake duct of the engine.

The collector 22 is fitted between two flanges 31 of a flange, generally designated 30, fitted and fixed by welding on the end 4.1 of the outer casing 4. The flanges 31 are parallel to the walls 4.5, 4.6 of the envelope 4 and are provided with bearings pivotally receiving an axis 32 of a double flap, generally designated 33, having two flap portions 33.1, 33.2 extending in the extension of one another on the other hand and other than axis 32.

The flange 30 and the flap 33 define an inlet opening 34 in the exchanger 1 facing the peripheral channels 10.a and an outlet opening 35 of the exchanger 1 facing the peripheral channels 10.b.

The flap 33 is mounted opposite the second duct 28 and the opening 34 and is movable between a bypass position (FIG. 3) in which the flap 33 deflects a gas flow coming from the second duct 28 directly to the first duct 24 without passing through the heat exchanger 1 and a connection position (Figure 2) in which the flap 33 guides the gas flow from the second conduit 24 to the inlet opening 34 and the outlet opening 35 to the first conduit 24.

In the connection position, the lateral and end edges of the flap portion 33.1 are respectively pressed against seat-forming surfaces 36, 37 extending into the manifold 22 and belonging to the valve body 21; the lateral and end edges of the flap portion 33.2 are in sealing engagement respectively against surfaces 38, 39 forming a seat and belonging to the flange 30. The surfaces 36, 37 extend on one side of the bearings opposite to the surfaces 38, 39. The flap 33 in connection position thus isolates the part of the manifold 22 into which the second conduit 28 of the portion of the manifold 23 into which the first conduit 24 opens. In the bypass position, the flap 33 deflects the gas flow directly 24. As the inlet and outlet of the exchanger both open into the valve body behind the flap, there is no circulation in the exchanger even if it is not not sealed with respect to the conduits 24, 28.

The surface 39 belongs to a crosspiece of the flange 30 which is integral with the shutter element 11 of the central channel 7. Due to the structure of the flange 30 and the distribution of the surfaces 36, 37, 38, 39 form seat of the flap 33 between the valve body 21 and the flange 30, the flange 30 is compact and makes it possible to obtain a small distance between the valve body 21 and the body 3 of the exchanger 1. The flange 30 is in a thermally conductive material and constitutes a thermal bridge between the valve body 21 and the body 3 of the exchanger 1.

To improve the heat exchange between the valve body 21 and the body 3 of the heat exchanger 1, the collector 22 is provided with a thermally conductive fin 29 which extends perpendicular to the axis 32 of the flap 33 and which comes to bear on the body 3 of the exchanger 1, here indirectly via the shutter element 11, made of thermally conductive material. The fin 29 thus promotes conduction between the body 3 of the exchanger 1 and the valve body 21.

The return element 13 and the flange 30 comprise end-pieces 14, 15 intended to extend opposite the apertures 8.1, 8.2 to allow the connection of pipes to the central channel 7. These end-pieces 14, 15 are welded on the walls 4.3, 4.4 and are intended to be connected to pipes carrying a heat transfer fluid. The central channel 7 thus conveys the coolant which will allow the cooling of the exhaust gases that will circulate in the peripheral channels 10. The central partitions 5 are thus in contact with the coolant and the gases to be cooled and allow a heat transfer direct between them, and the peripheral partitions 9 provide a heat transfer between the gases to be cooled and the heat transfer fluid via the central partitions 5. The use of a central channel for the coolant and peripheral channels surrounding the central channel for the fluid to be cooled provides a structure ¹ compact and efficient heat exchanger in facilitating heat transfer by convection and conduction. In addition, a single central channel for the heat transfer fluid limits the lengths to be sealed and minimizes the risk of leakage.

Note further that, the shutter member 11 being in contact with the coolant, the element promotes the cooling of the fin 29 and therefore the valve body 21. The components welded to the body 3 of 1 ' exchanger are laser welded.

According to a second embodiment, the valve assembly 2 and the return element 13 are arranged in such a way that the channels 10a extend from one side of the central channel 7 opposite the channels 10b. the figure 7).

According to a third embodiment, as represented in FIG. 8, the body 3 of the exchanger 1 comprises only four main peripheral channels 110 made in the mass of the body 3, each of these peripheral channels 110 being subdivided into a plurality of peripheral sub-channels 111 via a zigzag wall 112 attached in each peripheral channel 110. To create turbulence and increase the efficiency of the heat exchanger, these zigzag walls 112 may have reliefs, for example an embossing, to create turbulence in the gas flow.

Although the invention has been described in relation to a U-shaped heat exchanger, the invention is of course applicable to an I-shaped heat exchanger as in the fourth embodiment shown in FIGS. 9 and 10. One end of the body 203 of the exchanger is then connected to the valve body 221 which defines a single conduit 224 while the opposite end of the body 203 is connected to an external conduit by a connecting member 252.

In this arrangement, the central channel 207 is identical to the central channel 7 previously described, all the peripheral channels 210 of the body 203 of the exchanger are unidirectional and the body 203 of the exchanger comprises two additional channels, namely a bypass channel 250 uncooled and an isolation channel 251 containing air and thermally isolating the bypass channel 250 of the central channel 207. The valve body 221 of the valve assembly 202 is attached to the body 203 of the exchanger by a flange 230 having a single flap 233 movable between a connection position of the duct 224 to the peripheral channels 210 and a bypass position in which the duct 224 is connected to the bypass channel 250. Note that the isolation channel 251 is optional.

According to a fifth embodiment, represented in FIG. 12, the body 3 of the heat exchanger comprises two peripheral partitions 300, parallel to the walls 4.5, 4.6, having longitudinal edges connected to the walls 4.3, 4.4 to define with these and with the walls 4.5, 4.6 of the main channels 301 for the passage of the coolant. Between the peripheral walls 300 extend central partitions 302 defining central channels 303 of smaller section than the main channels 301 and for the passage of the gases to be cooled.

Of course, the invention is not limited to the embodiments described and variations can be made without departing from the scope of the invention as defined by the claims.

In particular, the body of the heat exchanger may have a structure different from that described and result for example from the combination of one or more of the embodiments described or result from an assembly of different parts obtained by extrusion molding. ... The number of channels may be different and the sections of those may not be rectangular. The outer envelope and the central channel may thus have a circular section and the peripheral channels a section into annular segments.

Alternatively, the body may comprise at least one extruded portion incorporating at least some of the partitions delimiting (in whole or in part) a plurality of channels. Thus, as shown in FIGS. 13 and 14, the body 3 of the exchanger can result from the assembly of several extruded parts (the body 3 remains an "extruded body" in the sense of the present description. we can see a first part extruded 3.A forming the envelope 4 and a second part 3.B delimiting the channels. Part 3.B comprises a central portion comprising the two central partitions 5 whose adjacent longitudinal edges are connected by partitions 5 'to delimit the central channel 7 which is only open at its ends before the introduction of the shutter elements 11, 12 (not visible here). Central partitions 5 extend the peripheral partitions 9. The part 3.B is mounted in the part 3.A in such a way that the walls 4.3, 4.4, 4.5 and 4.6 delimit the peripheral channels 10 with the peripheral walls 9. It is not necessary to fix the free longitudinal edges of the peripheral partitions 9 to the envelope 4, a sealing of the peripheral channels 9 with respect to each other is not necessary for the proper operation of the exchanger 1. on the other hand, the central channel 7 is longitudinally sealed before the assembly of part 4.8 in part 4.A, the risk of leakage of the coolant to be avoided.

It will be noted that ribs 70 project from peripheral partitions to increase the exchange surfaces with the gas flow.

In FIG. 14, two identical extruded portions can be seen forming half-bodies 3.A ', 3.B ¹ delimiting each: a longitudinal portion of the walls 4.3 and 4.4; one of the walls 4.5, 4.6; one of the central partitions 5 and the peripheral partitions 9.

The half-bodies 3.A ', 3.B' are joined to form the central channel 7 and are connected to one another by a longitudinal weld extending along the walls 4.3 and 4.4.

Furthermore, other welding methods than laser probing mentioned in the description of the preceding embodiments can be further used to the realization of the exchanger.

As a variant, the partitions of the body of the exchanger may locally have plastic deformations aimed at generating turbulence in the gas flow. These partitions may for example be corrugated as shown in FIG. 11.

The seat surfaces for the flap can be made on the flange only. Seat surfaces may also be provided on the valve body, either for only one of the positions of the flap, or for both positions of the flap.

In the connection position, the edges of the flap 33 may be spaced apart from the seat surfaces belonging to the valve body 21 and the flange 30 by a distance less than a minimum clearance clearance. This means that there is no impervious support of the flap on these surfaces but that a space extends between them, this space being of sufficiently small dimensions so that the resulting leakage is not detrimental to the operation of the heat exchange device. It is also possible to arrange the valve assembly so that the shutter in the bypass position cooperates with seat surfaces belonging to the valve body and / or the flange. The fin 29 is optional.

The flow direction of the gases in the valve assembly and the exchanger can of course be reversed with respect to that described.

The second duct may be delimited by the flange.

The circuit definition members may be mounted on the exchanger elsewhere than at its ends and for example in the vicinity of said ends.

Claims

1. Heat exchanger, characterized in that it comprises a body (3) delimiting a first channel (7) surrounded by peripheral channels (10), said exchanger being provided with independent circuit definition members (2, 11, 12, 13) arranged in such a way that the first channel allows the circulation of a coolant and the peripheral channels allow the circulation of a fluid to be heat treated. 2. Heat exchanger according to claim 1, wherein the first channel (7) is delimited laterally by at least one main partition (5) from which extend partitions (9) of the peripheral channels (10). 3. Heat exchanger according to claim 2, wherein the first channel (7) has a section greater than that of the peripheral channels (10). 4. Heat exchanger according to claim 2, wherein the first channel (7) forms a central channel of the exchanger. 5. Heat exchanger according to claim 4, wherein the body (3) comprises a tubular envelope (4) traversed by two parallel main partitions (5) laterally delimiting the first channel (7), the partition walls ( 9) peripheral channels (10) extending from the main partitions (5) to the envelope perpendicular to the main partitions. 6. Heat exchanger according to claim 5, wherein the first channel (7) has enlarged portions (7.1, 7.2) in the vicinity of the envelope. 7. Heat exchanger according to claim 6, wherein the first channel (7) opens out of the envelope (4) through openings (8.1, 8.2) in the envelope to open into the portions. widened (7.1, 7.2) of the first channel. 8. Heat exchanger according to claim 5, wherein the casing (4) has a rectangular section. 9. Heat exchanger according to claim 1, wherein the circuit defining members (2, 11, 12, 13) equip the ends (4.1, 4.2) of the body (3) of the exchanger.