FR3037387B1 - HEAT EXCHANGER FOR MOTOR VEHICLE - Google Patents

Abstract

The subject of the invention is a heat exchanger comprising a first circuit intended to be traversed by a liquid heat-transfer fluid and a second circuit intended to be traversed by a supercritical refrigerant fluid, in which the first circuit is formed by at least one channel ( A) delimited by at least two plates (1, 1 '), and wherein the second circuit is formed by at least one multichannel tube (B), the channel (A) being in contact with the tube (B). Advantageously, in this exchanger, the first circuit comprises several channels (A) and the second circuit comprises several tubes (B), and the tubes (B) and channels (A) are stacked alternately on each other. Such a heat exchanger finds a preferred application to air conditioning devices of motor vehicles.

Description

HEAT EXCHANGER FOR MOTOR VEHICLE

The field of the present invention is that of heat exchangers for motor vehicles, and the present invention applies more particularly, but not exclusively, to the heat exchangers used in the air conditioning circuits of these vehicles. The closest state of the art is formed by the two-circuit heat exchangers, in which a first circuit contains a heat transfer fluid of the brine type, and in which a second circuit contains a refrigerant, the calories being transferred from the coolant coolant fluid.

The refrigerant currently most used in this type of exchanger is a fluorinated compound known under the name R134a. This refrigerant fluid is usually maintained in a sealed closed circuit of the vehicle. In certain situations, however, this fluid can escape into the atmosphere: this is the case, for example, when the vehicle is damaged, or when the vehicle is at the end of its life, or when the refrigerant circuit has leak. However, this refrigerant fluid is known to contribute in a negative way to the greenhouse effect on the planet.

To overcome this drawback, it has been proposed to replace the fluorinated compound R134a with carbon dioxide known under the name R744 which has a much less negative impact on the greenhouse effect of the planet than that of the fluorinated compounds mentioned above. The implementation of this fluid with supercritical characteristics, however, imposes a number of technical constraints. Indeed, the thermodynamic cycle of CO2 requires, for obtaining a cooling effect corresponding to the requirements of the application, the implementation of high pressures, typically of the order of 160 bars. Plate heat exchanger technologies used for fluorinated refrigerants do not withstand these pressures.

The object of the present invention is to provide a simple, effective and reliable solution for performing a high-performance heat exchange between a heat transfer fluid and a supercritical refrigerant fluid such as carbon dioxide, which solution is also easy to assemble before operations welding / brazing of the heat exchanger.

For this purpose, the subject of the invention is a heat exchanger comprising a first circuit intended to be traversed by a liquid heat transfer fluid and a second circuit intended to be traversed by a supercritical refrigerant fluid, characterized in that the first circuit is formed by at least one channel delimited by at least two plates, and in that the second circuit is formed by at least one multichannel tube, and wherein said channel is in contact with the multichannel tube.

According to a preferred embodiment of the invention, the first circuit comprises several channels and the second circuit comprises several tubes, and the tubes and channels are stacked alternately on each other.

Advantageously, the multichannel tube is an extruded tube of low height, of the order of a few millimeters at most, in particular between 1 and 3 millimeters. According to one embodiment of the invention, the multichannel tube comprises a plurality of walls, and these walls define a set of channels that extend from one longitudinal end of said multichannel tube to the other. Advantageously, the channels thus delimited are straight and aligned next to each other.

According to another characteristic of the invention, the two plates forming a channel of the first circuit of the heat exchanger are assembled to each other at least by their periphery, in particular by a peripheral edge of these plates. The first circuit comprising a plurality of channels of this type, two plates forming a first channel of the first circuit and two plates forming a second channel of said first circuit communicate with each other by collars fitted into one another and assembled in a sealed manner. The internal volume of adjacent channels is thus put in fluidic relationship.

Each plate entering the formation of a channel of the first circuit has two orifices placed at each longitudinal end of the channel and each delimited by a collar which extends, once said plate is assembled with a similar plate to form said channel, towards outside said channel, that is to say towards the outside of the internal volume delimited by two plates forming a channel.

According to one embodiment of the invention, the plates which, by assembly, form the first circuit, also comprise one or more reinforcements which delimit heat transfer fluid circulation passages, these reinforcements being located in the central portion of the plate called bowl.

According to another characteristic of the invention, the contact between the elements forming the first circuit and the elements forming the second circuit is formed between at least a flat portion of a plate forming a part of a channel of the first circuit and at least a portion of an outer face of a multichannel tube forming the second circuit.

According to one aspect of the invention, a direction in which extends at least one channel forming the second circuit of said heat exchanger and a direction passing through orifices formed at each longitudinal end of a plate are substantially perpendicular to each other. The assembly, or the series, of first orifices and the assembly, or the series, of second orifices respectively form, once all the channels assembled in a sealed manner by said collars, a first tubular passage and a second tubular passage. which connect together all the internal volumes of the channels.

According to one embodiment of the invention, each plate entering the formation of a channel of the first circuit comprises at least one rib which delimits at least one circulation passage of the coolant. Such a rib also has a function of mechanical reinforcement of the channel. In one example, each rib has substantially the shape of a "V", thus forming a chevron.

In the interposed stack of multichannel channels and tubes, each end of the multichannel tubes protrudes from edges located at the periphery of the constituent plates of the channels. The multichannel tubes can thus be connected to collector boxes without interfering with the plates.

According to the invention, each plate entering the formation of a channel of the first circuit comprises at least a flat portion in contact with an outer face of a multichannel tube. This ensures the transfer of heat from the liquid heat transfer fluid to the supercritical refrigerant fluid, or in the opposite direction. Other characteristics, details and advantages of the invention will emerge more clearly on reading the description given below as an indication, in relation to drawings in which: FIG. 1 is an external perspective view of two plates entering the formation of a channel of the first circuit of a heat exchanger according to the invention, - Figure 2 is a close perspective view of a detail of the assembly of two channels of the first circuit of a heat exchanger FIG. 3 is a perspective view of the assembly of the channels forming the first circuit and of the tubes forming the second circuit of a heat exchanger according to the invention, FIG. schematic perspective view of a multichannel tube used in the formation of the second circuit of a heat exchanger according to the invention, - Figure 5 is a closer view of a detail of the multichannel tube shown in Figure 4, - the f FIG. 6 is a perspective view of the assembly of two elements of the first circuit and an element of the second circuit of a heat exchanger according to the invention; FIG. 7 is a schematic perspective view of the two circuits of FIG. An exchanger according to the invention, assembled, - and Figure 8 is a schematic side view of a complete heat exchanger according to the invention. It should first be noted that the figures show the invention in detail to implement it, said figures can of course be used to better define the invention where appropriate.

In the remainder of the description, the designation "inside" refers to the volumes in which circulate either the coolant or the coolant.

FIG. 1 shows an external perspective view of two plates 1 forming part of a channel A of the first circuit of a heat exchanger 100 according to the invention, capable of being traversed by a coolant such as a glycol fluid. , for example. It should be understood here that a channel A of this first circuit is formed of the assembly of these two plates 1 as shown in FIG.

Each plate 1 is a thin plate, advantageously made by stamping a metallic material so as to form a bowl 10 (visible in Figure 2) of shallow depth delimited by a bottom 12 and, peripherally, by an edge 11. A As an indication, the thickness of each plate 1 is advantageously of the order of a few tenths of a millimeter, typically, but in a nonlimiting manner, 3 / 10® to 7 / 10® millimeter. The depth of the bowl 10 is advantageously of the order of a few tenths of a millimeter to about 1 millimeter. The edge 11, raised relative to the bottom 12 of the bowl 10 when viewing the inner part of the plate 1, forms a blank 110 of small width, substantially parallel to the bottom 12, and extending outwardly of the bowl 10. Once the two plates 1 assembled to delimit a channel A, the thickness thereof measured to the right of the cups 10 is between 1 and 3 millimeters.

According to the embodiment, non-exclusive, shown in the figures, each plate 1 has substantially the general shape of a hexagon of which two parallel sides 1a and 1b are longer than the other sides, the lengths of said other sides being substantially equal between they.

Each plate 1 is also pierced with two orifices, hereinafter called first orifice 13a and second orifice 13b. In the example illustrated by the figures, the orifices 13a and 13b have an oblong shape and are placed substantially at each end of the plate 1, substantially spaced from the length of the parallel sides 1a and 1b. They are also placed in such a way that the plate 1 has at least one plane of symmetry P. In the example illustrated by the figures, the plane of symmetry P is substantially perpendicular to the parallel sides of greater length 1a and 1b, and go through the middle of these.

Each orifice 13a, 13b has, at its periphery, a collar 13c which extends outwardly of the plate 1, opposite to the direction in which the edge 11 extends with respect to the bottom 12 of the bowl 10 Between the first orifice 13a and the second orifice 13b, each plate 1 may also have a plurality of ribs 14 each of which, in the bowl 10, forms a projection whose height is slightly less than the depth of the bowl 10. According to the embodiment of the invention illustrated by the figures, the ribs 14 are arranged symmetrically with respect to the plane of symmetry P previously mentioned, and they each have the shape of a "V". In other words, these ribs 14 each form a chevron. By their shape, these ribs 14 have a role of mechanical reinforcement and stiffening of each plate 1. They also have another role to be specified later. Between the ribs 14, the bottom 12 of each plate 1 is substantially plane.

To form a channel A of the first circuit of the heat exchanger according to the invention intended to be traversed by the liquid heat transfer fluid, two plates 1 as described above are assembled by their edge 11. More specifically, the blanks 110 two plates 1 are contiguous and brazed together, so that the two cuvettes 10 of each plate 1 together form an internal volume V in which the liquid heat transfer fluid is called to circulate. Given the depth of each bowl 10, the height of a channel A is typically, but not limited to, of the order of 1 to 3 millimeters. However, it follows from the description of the plates 1 above that the internal volume V defined by the assembly of the latter communicates with the outside through the orifices 13a, 13b carried by them.

According to one characteristic, the first circuit of the heat exchanger according to the invention consists of a stack or succession of several channels as described above. Figure 2 shows a detail of the assembly of two immediately adjacent plates constituting two channels forming the first circuit. It appears in FIG. 2 that, during the assembly of the two adjacent channels A, the orifices 13a formed on the plates 1 are facing one another, and that their collars 13c, which then extend towards each other, cooperate to form a passage portion for communicating with each other the internal volumes V formed within the adjacent channels. When assembling these channels together, the collars 13c, brazed together, thus form a sealed passage between the internal volumes V of said channels each delimited by a pair of plates 1. It will be noted that the collar 13c of a first channel A is fitted into the neck 13c of a second channel A immediately adjacent. These successive sealed passages form, with the succession of channels assembled to form the first circuit of the heat exchanger according to the invention, a first tubular passage 15a delimited by the series of first orifices 13a visible in FIG. 3 through which the heat transfer fluid can flow to enter or leave each channel forming the first circuit.

Each plate 1 having a first orifice 13a and a second orifice 13b at each of its ends, a second tubular passage 15b is formed in the same manner as the first tubular passage 15a, as shown in FIG. 3, that is to say say by the series of second orifices 13b. These tubular passages 15a and 15b form, with the succession of internal volumes V channels A assembled to form the first circuit of the heat exchanger 100 according to the invention, the first heat transfer fluid circuit. It will be noted here the advantage of arranging the first orifices 13a and the second orifices 13b so that they are as far apart as possible from each other on each plate 1, so as to increase as much as much as possible the length traveled by the coolant and, thus, so as to improve the efficiency of the heat exchange.

Another role of the ribs 14 formed on the plates 1 also appears here. The presence of these ribs, projecting within the different internal volumes V stacked channels A, disrupts the laminar circulation of the heat transfer fluid by creating turbulence of the fluid within the internal volume V. This results in an optimization of the contact surface between the circulating coolant and the inner surface of the channels A and, thus, an improvement of the efficiency of the heat exchange by the generation of turbulence favoring the heat exchange between the liquid fluid and the plates 1 delimiting the A channel

Figure 3 also illustrates the presence of a plurality of multichannel tubes B interposed between each channel A of the first circuit. The multi-channel tubes B are connected in leaktight manner to one or more inlet and outlet sleeves 7a and 7b connected to a single flange 50. Between these inlet and outlet sleeves 7a and 7b and the multichannel tubes B is a collecting box 51 consisting of a stack of components. One of these components is a first plate 5 on one side of which the inlet sleeves 7a and 7b outlet are directly secured. Another component is formed by an intermediate plate 52 sandwiched between the first plate 5 and a header plate 6. The latter comprises folded longitudinal edges for gripping the first plate and thus maintain the stack of components.

Figures 4 and 5 show schematic views of a multichannel tube B entering the formation of the second circuit of the heat exchanger 100 according to the invention. According to the embodiment of the invention, non-exclusive, illustrated by the figures, a multichannel tube B, which is advantageously an extruded tube, is in the form of a rigid plate 20 of generally rectangular shape of large side L , of small side I, and of thickness d. According to the invention, this plate comprises, in its thickness, a set of walls 22, for example parallel, of width h1 which extend, in a direction D1 parallel to that of the long side L of the multichannel tube B, of a longitudinal end to the other of the plate 20.

The walls 22 form bridges of material between two large outer faces 33 and 34 defined by the long side L and the short side I. The walls 22 delimit between them, in the direction D1, a set of channels 21 aligned parallel to each other. extend, also in the direction D1, from one longitudinal end of the plate 20 to the other, so as to open at both ends thereof. In section along a plane perpendicular to the long side L of the multichannel tube B, and as shown more precisely in FIG. 5, each of the channels 21 has a substantially oblong shape whose height H is greater than the width h and slightly less than thickness d of the rigid plate 20. In a direction D3 substantially parallel to that of the small side I of the rigid plate 20, the channels 21 are spaced from each other by the width h1 of each wall 22, and each of these walls plays a role of mechanical reinforcement of the entire multichannel tube B, the channels 21 being aligned side by side.

FIG. 6 more precisely illustrates the connection between two channels A of the first circuit of the heat exchanger 100 according to the invention and a multichannel tube B of the second circuit of this heat exchanger. It appears in this figure that the multichannel tube B is interposed between the two channels A, and that the multichannel tube B protrudes, at each of its ends, longitudinal edges 1a, 1b of greater length of each of the channels A. More precisely , and as mentioned above, the outer wall of the bowl 10 formed in each plate 1 forming a channel A is between the ribs 14 that this plate carries, substantially planar. According to the invention, at least a portion 35 of these flat portions is in direct contact, in particular by soldering, with an outer face 33 or 34 of the immediately adjacent multichannel tube B.

Advantageously, the dimensions of the flanges 13c of adjacent channels A and the thickness d of each multichannel tube B are defined in such a way that the insertion of these tubes between two adjacent channels A is possible while leaving a space of small dimensions such that it is possible to achieve direct contact by simple welding or soldering between multichannel tube B of the second circuit and plates 1 of the channels of the first circuit. According to a preferred embodiment of the invention, not limiting, the thickness d of each plate 20 is of the order of 1 to 3 millimeters, corresponding to the space between two immediately adjacent channels A of the first circuit.

As shown in Figures 3, 7 and 8, the first and second circuits of a heat exchanger 100 according to the invention are formed of a succession of channels A and multichannel tubes B interposed between two adjacent channels, the tubular passages 15a and 15b defining an inlet and an outlet of the coolant in the first circuit and thus a general direction of circulation of said fluid in said first circuit.

The supercritical refrigerant circulates in the channels 21 of the multichannel tubes B in the second circuit. Referring to Figures 7 and 8, an inlet cheek 3 is combined with a first plate 1 so as to define an inlet zone of the coolant in the first circuit. The inlet cheek 3 has a thickness greater than the thickness of a plate 1 and thus forms a mechanical reinforcement for the heat exchanger. The inlet cheek 3 receives an inlet pipe 31 also delimiting one of the tubular passages 15a or 15b. The heat exchanger 100 according to the invention also comprises an outlet cheek 4 sealed to a plate 1. This outlet cheek 4 supports an outlet pipe 41 delimiting the second tubular passage 15b. The heat transfer fluid therefore enters the first circuit through the inlet pipe 31, circulates in the first tubular passage 15, then is distributed in each channel A, to be collected by the second tubular passage 15b, and finally out of the exchanger heat 100 through the outlet pipe 41.

According to the advantageous embodiment illustrated by the figures, the inlet and the outlet of the heat transfer fluid circuit are each located at one end of the heat exchanger 100 according to the invention, according to the stacking direction of the assembly. multichannel channel tubes.

Similarly, the multichannel tubes B are connected, at each of their ends, to a manifold 51 as described in connection with Figure 3 above. Only one of two header boxes is connected to a set of inlet and outlet sleeves 7a and 7b, which ensure the circulation of supercritical refrigerant fluid in the second circuit of the heat exchanger according to the invention. It is thus understood that the inlet and outlet sleeves 7a and 7b of the second circuit are situated on the same side of the heat exchanger, thus defining a "U" configuration of this second circuit. The manifold without inlet and outlet sleeves 7a and 7b, said recovery collecting box 53, ensures the recovery of the supercritical refrigerant fluid arriving through a portion of the channels 21 of the multichannel tubes B. This manifold then directs the fluid of so that it enters the other part of the channels 21 to go to the manifold 51, said header manifold.

According to the invention, and as shown in FIG. 6, a general direction D2 of circulation of the coolant in the channels A constituting the first circuit is defined by a straight line passing through the first orifice 13a and the second orifice 13b of the same plate 1. This direction D2 is perpendicular, or substantially perpendicular, to the general direction D1 supercritical refrigerant circulation in the multichannel tubes B, defined by the orientation of the channels 21 of the multichannel tubes B. In other words, at the at least one channel A of the first circuit and at least one multichannel tube B of the second circuit are arranged in the heat exchanger 100 so that their respective fluid path is perpendicular, or substantially perpendicular.

The process for producing a heat exchanger 100 according to the invention can be as follows: stacking of the channels A and multichannel tubes B so as to form a heat exchange body, forming respectively the first and the second fluid circuit, pre-assembly of the manifolds 51, pre-assembly of the inlet pipes 31 and outlet 41 on the stack of multichannel tubes B, pre-assembly of the inlet sleeves 7a and outlet 7 on the stack of the channels A, then brazing or welding the assembly in a suitable oven. The invention therefore makes it possible to produce a single monobloc exchanger whose elements in which the supercritical refrigerant fluid circulates are designed to withstand the high pressures necessary for the implementation of the latter, while offering high heat exchange performance. According to the embodiment described, the manufacturing operations of the various elements of the circuits of the heat exchanger such as the stamping of the plates forming the channels of the heat transfer fluid circuit, the extrusion of the multichannel tubes, the soldering of the assembled elements, the pre-assembly steps and the final soldering step are, moreover, simple and cost-effective for mass production. Such a heat exchanger 100 remains economically viable for mass production, as is particularly the case in the world of automotive production. In addition, such an exchanger is of limited size, which facilitates its integration into a vehicle, and allows its installation on a wide variety of vehicles. Of course, it should be noted that the invention can not be reduced to the means and configurations described and illustrated, but that it also applies to any equivalent means or configurations and any combination of such means. In particular, if, in the example described by this document, the inlet and outlet sleeves 7a and 7b of the second circuit of the heat exchanger 100 according to the invention are situated on the same side of this exchanger, defining a circulation of the refrigerant fluid "U", such a configuration is not exclusive, and the inlet and outlet sleeves of the second circuit can be arranged to define an "I" configuration without affecting the invention . In this case, an inlet sleeve 7a is secured to a first manifold 51, and an outlet sleeve 7b is secured to a second manifold 53. Any other respective configuration of the inlet or outlet sleeves or pipes the first or second circuit can also be implemented, as it helps to optimize the circulation of heat transfer fluids and supercritical refrigerant and, thus, the efficiency of heat exchange. Similarly, any general shape other than hexagonal can be given to the plates 1 entering the formation of the channels A, insofar as the specificities of these plates described here with respect to the invention are respected.

Claims (14)

Heat exchanger (100) comprising a first circuit intended to be traversed by a liquid heat transfer fluid and a second circuit intended to be traversed by a supercritical refrigerant fluid, the first circuit being formed by at least one channel (A) delimited by at least two plates (1), the second circuit being formed by at least one multichannel tube (B), said at least one channel (A) being in contact with said at least one multichannel tube (B), each plate (1) entering the formation of a channel (A) of the first circuit comprising at least one rib (14) * which delimits at least one circulation passage of the coolant, each rib (14) having substantially the shape of a "V" . 2. Heat exchanger according to claim 1, characterized in that the first circuit comprises several channels (A), in that the second circuit comprises a plurality of multichannel tubes (B), and in that the multichannel tubes (B) and channels (A) are stacked alternately on each other. 3. Heat exchanger according to either of claims 1 or 2, characterized in that each multichannel tube (B) is an extruded tube whose thickness (d) is between 1 and 3 millimeters. 4. Heat exchanger according to any one of claims 1 to 3, characterized in that each multichannel tube (B) comprises a plurality of walls (22) which delimit between them a set of channels (21) extending from one end of said multichannel tube (B) to the other. 5. Heat exchanger according to claim 4, characterized in that the walls (22) and channels (21) of each multichannel tube (B) extend, in a general direction (D1), straight and aligned parallel to each other. next to others. 6. Heat exchanger according to claim 5, characterized in that the direction (D1) in which extend at least one channel (21) forming the second circuit of said exchanger and a direction (D2) passing through orifices (13a, 13b). ) at each longitudinal end of a plate (1) are substantially perpendicular to each other. 7. Heat exchanger according to any one of claims 1 to 6, characterized in that two plates (1) forming a channel (A) of the first circuit are assembled together with each other in a sealed manner at least by their edge (11). 8. Heat exchanger according to any one of claims 1 to 7, characterized in that each plate (1) entering the formation of a channel (A) of the first circuit has two orifices (13a, 13b) placed at each its longitudinal ends and each delimited by a collar (13c) which extends, once said plate joined with a similar plate to form said channel (A), outwardly of said channel (A). 9. Heat exchanger according to claim 8, characterized in that the channels (A) of the first circuit communicate with each other by the collars (13c) assembled together by fitting. 10. Heat exchanger according to any one of claims 8 to 9, characterized in that a plurality of first orifices (13a) and a plurality of second orifices (13b) respectively form, once the set of channels (A ) assembled in a sealed manner by said collars (13c), a first tubular passage (15a) and a second tubular passage (15b) which connect together all the internal volumes (V) of the channels (A). 11. Heat exchanger according to any one of claims 1 to 10, characterized in that, in the interposed stack of channels (A) and multichannel tubes (B), each end of the multichannel tubes (B) protrudes from edges ( 11) located at the periphery of the plates (1) constituting the channels (A). 12. Heat exchanger according to any one of claims 1 to 11, characterized in that each plate (1) entering the formation of a channel (A) of the first circuit of said exchanger comprises at least one planar portion (35). in contact with an outer face (33) of a multichannel tube (B). Coolant circuit for a motor vehicle, characterized in that it comprises a heat exchanger (100) according to any one of claims 1 to 12. 14. supercritical refrigerant circuit for a motor vehicle, characterized in that it comprises a heat exchanger (100) according to any one of claims 1 to 13.