FR2938322A1 - Heat exchanger i.e. exhaust gas cooler, for cooling exhaust gas in exhaust gas recirculation circuit of heat engine, has protecting shell that is in intimate contact with rectilinear profile on region of shell clasping profile - Google Patents

Abstract

The exchanger (16) has an extruded rectilinear profile (21) provided with a primary fluid intake pipe (23) and a primary fluid outlet pipe (24). An aluminum protecting shell (22) surrounds the profile by clasping the profile on a region covering a major part of outer surface of the profile. A cylindrical outer envelope (17) surrounds the shell. The shell is in intimate contact with the profile on the region of shell clasping the profile, where an end of the profile is fixed to a gas collector (19). An independent claim is also included for a method for fabrication of a heat exchanger.

Description

Heat exchanger comprising a profile including pipes and a shell surrounding this profile

The invention relates to a heat exchanger for cooling the exhaust gas of a recirculation circuit of these gases equipping a heat engine, also known under the acronym EGR meaning "Exhaust Gas Recirculation". BACKGROUND OF THE INVENTION Such a known exchanger, represented diagrammatically in FIG. 1 by being indicated by 1, comprises a generally cylindrical envelope 2 provided with a curved bottom 3 closing one of its ends, a collector 4 of connection to the exhaust gas recirculation circuit closing the other end of this envelope, and a main body 6 surrounded by the enclosure defined by the envelope 2 and the collector 4. The collector is provided with a first inlet mouth 7 for the gas to be cooled, and a second outlet 8 for discharging the cooled gas, as well as a movable valve 9. This valve 9 is movable between a first so-called cooling position, which it occupies in FIG. 1, and a second position not shown, called bypass.

When the valve is in the first position, it directs the gas admitted by the first mouth 7 to the main body 6 so that it is cooled before being discharged by the second mouth 8. When it occupies the second position, the gas admitted is directly transferred to the second mouth without being cooled. As shown in Figure 1, the main body 6 comprises said intake pipes identified by 11, and said discharge pipes marked by 12, extending parallel to the longitudinal direction AX, between the bottom 3 and the collector 4 .

This main body also comprises a cooling water passage circuit 13, in which water circulates which cools this main body. In operation, the gas is cooled as it traverses the so-called inlet and outlet pipes of the main body, which is itself cooled by the cooling water. The gas admitted by the first mouth 7 engages in the intake ducts 11, via their ends located opposite the collector 4, it traverses these ducts 11 until reaching their other ends located in screws. 3 to the bottom of the casing 2, to open into a return chamber 14. The gas passing through the chamber 14 then enters the ends of the discharge pipes 12 which are also located opposite each other. of the bottom 3 and communicate with the chamber 14, then it traverses these pipes 12 to reach their other ends located opposite the collector 4, before being discharged via the second mouth 8. OBJECT OF THE INVENTION The purpose of the invention is to propose an exchanger architecture that significantly reduces its cost of manufacture without penalizing its thermal performance. SUMMARY OF THE INVENTION To this end, the subject of the invention is a heat exchanger, for transferring heat between a first fluid and a second fluid, comprising a series of circulation ducts of the first fluid, and a circulation circuit of the first fluid. second fluid for transferring heat between the two fluids, characterized in that it comprises an extruded rectilinear profile comprising the ducts of the first fluid, and a protective shell surrounding the profile by enclosing it on a region covering most of the outer surface of this profile, an outer shell surrounding the shell, the second fluid circulating between the shell and the shell, and in that over the entire region where the shell encloses the profile, the hull is mechanically constrained on this profile and / or welded to this profile. The shell is thus firmly pressed to the profile over the entire surface by which it is in contact with it. Air or gas can not be trapped between the shell and the profile, so that the junction between shell and profile does not introduce additional thermal resistance that could degrade the efficiency of the exchanger. The invention also relates to an exchanger as defined above, wherein over the entire region where the shell encloses the profile, it is mechanically constrained to this section. The invention also relates to an exchanger as defined above, wherein over the entire region where the shell encloses the profile, it is welded to this profi- le. The invention also relates to an exchanger as defined above, wherein the shell is made of anodized aluminum on its inner face. The invention also relates to an exchanger as defined above, wherein the shell has a sleeve shape surrounding the rectilinear profile over its entire length. The invention also relates to an exchanger as defined above, wherein the rectilinear profile comprises a series of inlet ducts of the first fluid and a series of discharge ducts of the first fluid, each duct having a de-plugging end in a return chamber closed by a bottom of the hull, the first fluid passing through this return chamber to be transferred from the intake lines to the discharge lines. The invention also relates to an exchanger as defined above, comprising a collector located at the end of the rectilinear profile, and wherein an end of the shell also surrounds a portion of this collector, and in which over the entire region surrounding this part of the collector, the shell is mechanically constrained to the collector and / or welded to the collector. The invention also relates to an exchanger as defined above, wherein the envelope comprises at least one circumferential rib formed by folding or stamping, and by which this envelope is in contact with the shell. The invention also relates to an exchanger as defined above, in which the rib extends along a curve corresponding to the projection on the shell of a helicoid of the same axis as this shell for channeling the second fluid circulating between the hull and the envelope. The invention also relates to an exchanger as defined above, wherein the shell is fixed by magnetoforming on the profile and optionally on the collector. The invention also relates to an exchanger as defined above, in which the envelope is mounted on the collector by magnetoforming. BRIEF DESCRIPTION OF THE FIGURES - FIG. 1 is a representation of a state of the art exchanger; - Figure 2 is a side view in section and exploded showing the manifold and the section and the shell and the shell of the exchanger according to the invention; - Figure 3 is a representation of the section of the exchanger of Figure 2 in side view with a portion of its shell and in front view; - Figure 4 is a representation of another section for the exchanger according to the invention in a side view with a part of its shell; - Figure 5 is a sectional side view showing the profile and the collector and the shell of the exchanger according to the invention once assembled; FIG. 6 is a schematic representation of the magnetoforming process used to assemble the exchanger according to the invention; FIG. 7 is a sectional side view showing the profile with the collector and the shell and the shell of the exchanger according to the invention once assembled; - Figure 8 is a sectional side view showing a variant of the exchanger according to the invention. DETAILED DESCRIPTION OF THE INVENTION The idea underlying the invention is to join the gas pipes in an extruded section bathed in the coolant, providing a shell protecting the outer surface of this profile to prevent corrosion. due to the gas can not put in communication the liquid cooling circuit with the circulation circuit of the gas. In order to reduce the thermal resistance of the interface between the protective shell and the outer surface of the profile, this shell is mounted in force around the profile and / or welded over its entire contact surface. The shell is thus firmly secured to the ex-dull surface of the profile, which reduces the thermal resistance of the junction by avoiding the presence of air in this junction.

With this solution, it is not necessary to anodize the extruded profile comprising the gas lines: the protection against corrosion caused by the exhaust gas is provided by the hull. This shell can be made of different materials, for example anodized aluminum, stainless steel, or other. The exchanger according to the invention, which is visible in exploded form in FIG. 2, is marked by 16 and comprises a cylindrical envelope 17 with a rectangular base, provided with a bottom 18 closing one of its ends, a collector 19 of gas, an extruded section 21 and a protective shell 22 for surrounding this section. When the whole is assembled, as in FIG. 7, the shell 22 surrounds the profile 21, one end of which is attached to the collector 19, and the envelope surrounds the profile 21 and its shell, and the end of the envelope which is opposed to its bottom 18 is fixed to the manifold 19. As shown in Figure 3, the section 21 comprises the gas inlet ducts identified by 23 and the gas discharge pipes which are identified by 24, these ducts s extend parallel to the longitudinal axis AX of the exchanger 16 and are located respectively on either side of a median plane parallel to this axis.

All these conduits open on the one hand to the end of the section 21 which is opposite the collector 19, and on the other hand to the opposite end of this pro-spun. This other end is cut to have a V-shape in side view, and it is closed by a bottom 28 of the protective shell 22 to define together with this bottom, a return chamber 26. The manifold 19 comprises a pipe 25 in which it receives the gas to be cooled in order to introduce it into the intake ducts 23, via their ends located opposite this manifold 19, this gas then flows through the ducts 23 until reaching their other ends located opposite the bottom 28 of the shell to open into the return chamber 26. After passing through the chamber 26, the gas enters the ends of the discharge pipes 24, which are located vis-à-vis the bottom 28 to communicate with the chamber 26, and it traverses these pipes 24 until reaching their other ends located opposite the collector 19, before being discharged at the level of an outlet pipe 27 of the collector 19. In the example of Figures 2 and 3, the end of the profile corresponding to the return chamber 26 is cut Vee being closed by a bottom 28 of shell which is flat. But other forms of the return chamber are possible, as in the example of Figure 4 where the end of the section 29 is straight being closed by a curved shell bottom 31 to define a return chamber 32 As shown in Figure 5, the manifold 19 comprises a base 33 extended by a sleeve 34 having a cross section approximately identical to that of the section 21 which is placed in the extension of this sleeve. The shell 22 surrounds the profile 21 all along the axis AX, its end which comprises the bottom 28 closes the end of the profile 21 opposite the manifold 19, and the open end of this shell extends along the sleeve 34. This shell surrounds the profile over its entire length, and the sleeve 34, so that they are thus held fixed to each other. The shell 22 is attached to these elements by being mounted tightly, that is to say by being mechanically constrained to them and / or being welded thereto. This assembly can be provided by magnetoforming, ie according to the method illustrated schematically in FIG. 6. According to this method, a tubular piece 36 is mounted on a body 37 which it surrounds by applying a magnetic field. brief and intense. The raw tubular piece 36 whose inner section is greater than the outer section of the body 37, is first positioned around the body 37, the assembly being surrounded by an electric coil 38.

The injection of an intense and short electric current I into the coil 38 gives rise to currents in-ducts at the tubular part 36, which results in a so-called magnetic pressure which is centripetal, that is to say it tends to retract the tubular part 36 on the body 37. This mounting solution ensures optimum cohesion between the shell 22 and the profile 21 over the entire bearing surface of the shell 22 on the section 21. According to the parameters of the magnetotroping operation chosen, the shell can be either simply mechanically constrained on the section, ie mounted in force on it, or welded thereto, all over the face of contact. The junction between the shell and the outer face of the profile thus has no air, which helps to minimize the resistance opposed by this junction to the passage of heat transferred from the gas to the coolant. As can be seen in FIG. 5, the edge or collar of the open end of the shell 22 can also be fixed to the manifold 19 by magnetoforming, which then makes it possible to assemble in a single operation the shell 22 with the profile 21 and the The parameters used for magnetoforming to retract the shell may differ for the region of the shell which encloses the profile and for the region of the shell, namely its end, which encloses the sleeve 34 of the manifold 19. For example, less powerful magnetoforming can be provided at the interface between the shell and the profile, and more powerful magnetoforming, ie producing a higher magnetic pressure at the collar of this shell. In this case, the magnetization provides a simple assembly of the shell 22 on the section 21, while it provides a mounting up to the welding of the shell on the sleeve at the collar of the shell. Advantageously, it also provides sealing elements such as O-rings 41 and 42 which are interposed between the sleeve 34 and the shell 22, one being located at the end of the collar 39, and the other at level of the limit between the sleeve 34 and the section 21. Other elements can also be interposed between the shell and the profile, to further reduce the risk of leakage or to break the thermal or electro-chemical bridges may appear. The envelope 17 surrounding the profile 21 and the shell 22 may also be made of a material that is compatible with the magnetoforming, ie having a high electrical conductivity, as in the example of FIG. to be fixed to the manifold 19 by magnetoforming. In this case, the collar 43 of this envelope is sized to surround the base of the collector 19, or an additional sleeve of the collector provided for this purpose. As for the mounting of the shell, the envelope is then positioned so that collar 43 surrounds the base 33, and the assembly is subjected to a magnetic field short and powerful to ensure cohesion, for example up to to reach the welding. A coolant passage 44 can then be provided at the base 33, being located between the sleeve 34 and the periphery of the base, to supply water to the space between the shell and the envelope. This feature also makes it possible to also ensure the cooling of the collector, as in FIG.

In this context, the rest of the envelope 17 may have an optimized shape to ensure other functions since the attachment of this envelope 17 to the rest of the exchanger is provided only by its collar 43 which is tight and / or welded on the base 33.

This envelope 17 may then comprise one or more ribs made for example by folding or stamping, to locally reduce its internal diameter, so that it bears on the ex-dull surface of the shell 22 in order to focus on that This guarantees a minimum space for passage of water between the shell and the envelope. Advantageously, this folding, which is indicated by 46, has a general shape corresponding to the projection on the shell of a helical axis AX, for channeling water between its inlet point 44 located at the collector, and its outlet point 47 located at the end of the shell closed by the bottom 28. In general, the section 21 can be made of extruded aluminum, without having to be anodized.

It is then the shell 22 which is made of anodized aluminum on its inner face, and possibly on its outer face, so as to avoid drilling of the profile and this shell, caused by the corrosion of the exhaust gas condensates.

In the example of Figures 2 to 7, the invention is applied to a heat exchanger in which the gas travels back and forth in the profile. But the invention applies to other architectures of exchangers, such as the exchanger 48 of Figure 8. This exchanger comprises a section 49 provided with pipes 51 and a first and a second collector 52 and 53 located at each end of this profile. The gas is introduced through the first manifold 52 at one of the ends of the section, and it is discharged at the other end of this section, via the second manifold 53. The shell 54 of this exchanger 48 is here tubular, it is ie open at both ends. It surrounds the profile 49, and the edge or collar of each of its ends, marked 56 and 57 respectively surround a sleeve 58 of the first collector, and a sleeve 59 of the second collector. Four O-rings 61 are interposed between the shell and each sleeve. The assembly is surrounded by a casing 62 of generally tubular shape, that is to say open at both ends, each edge of this casing surrounding a base of one of the collectors to be fixed thereto. This envelope also has an inlet and a coolant outlet 63 and 64 extending radially relative to the longitudinal axis AX of the exchanger. In a similar manner to the example of FIGS. 2 to 7, the shell 54 is fixed by magnetoforming to the profile and to the collectors, and the envelope 62 also has its extremities fixed by thermoforming to each collector.

Claims (11)

REVENDICATIONS1. A heat exchanger (16; 48) for transferring heat between a first fluid and a second fluid, comprising a plurality of first fluid flow conduits (23, 24; 51), and a second fluid flow circuit for transferring heat heat between the two fluids, characterized in that it comprises an extruded straight section (21; 49) comprising the conduits of the first fluid (23, 24; 51), and a protective shell (22; 54) surrounding the profile by tightening it over a region covering most of the external surface of this profile, an outer envelope (17, 62) surrounding the shell (22; 54), the second fluid circulating between the envelope (17; 62) and the shell (22; 54), and in that over the entire region where the shell (22; 54) encloses the profile (21; 49), the shell (22; 54) is in close contact the profile (21; 49). 2. Exchanger according to claim 1, in which over the entire region where the shell (22; 54) encloses the profile (21; 49), it is mechanically constrained on this profile (21; 49). 3. Exchanger according to claim 1 or 2, wherein over the entire region where the shell (22; 54) encloses the profile (21; 49), it is welded to this profile (21; 49). 4. Exchanger according to one of claims 1 to 3, wherein the shell (22: 54) is made of anodized aluminum on its inner face. 5. Exchanger according to one of claims 1 to 4, wherein the shell (22; 54) has a sleeve shape surrounding the rectilinear profile (21; 49) along its length. 6. Exchanger according to one of claims 1 to 5, wherein the rectilinear profile (21) comprises a series of inlet ducts (23) of the first fluid and a series of discharge pipes (24) of the first fluid, each pipe. (23, 24) having an end opening into a return chamber (26) closed by a bottom (28) of the shell (22), the first fluid passing through this return chamber (26) to be transferred from-then the intake ducts (23) to delivery lines (24), 7. Exchanger according to one of the preceding claims, comprising a collector (19; 52, 53) located at the end of the rectilinear section (21; 49), and in which one end of the shell (22; 54) also surrounds a portion of this manifold (19; 52,53), and wherein over the entire region (34) surrounding this portion of the manifold (19; 52,53), the shell is mechanically constrained to the manifold (19; 52, 53) and / or welded to the manifold (19; 52, 53). 8. Exchanger according to one of the preceding claims, wherein the casing (17) comprises at least one circumferential rib (46) formed by folding or stamping, and by which the casing (17) is in contact with the shell (22). ). 9. Exchanger according to one of the preceding claims, wherein the rib (46) extends in a curve corresponding to the projection on the shell (22) of a helicoid of the same axis as the shell (22) for channeling the second fluid circulating between the shell and the envelope. 10. A method of manufacturing an exchanger according to one of the preceding claims, wherein the shell is fixed by magnetoforming on the profile and optionally on the collector. 11. The method of claim 10, wherein the envelope is mounted on the manifold by magnetization.