FR2866948A1 - Heat exchanger e.g. heat radiator, for motor vehicle, has deviation plates of length selected such that their ends define deflector contour with convex portion complementary to concave portion of circumference of each hole of cooling fins - Google Patents

Abstract

The exchanger has a set of superimposed cooling fins, each with a surface perforated with holes (8) for passage of fluid circulating tubes. Circumference of each hole has a concave portion opposite to a deflector (30) formed of a set of longitudinal deviation plates (32). The plates are of length selected such that their ends define a contour of the deflector, with a convex portion complementary to the concave portion.

Description

VTM1519.FRD Enhanced flow deflector heat exchanger

  The invention relates to the field of heat exchangers as used in particular in automotive construction to provide cooling of an engine.

  The function of a heat exchanger is to provide a heat exchange between an internal fluid circulating in tubes and an external fluid passing through the heat exchanger.

  In order to increase the heat exchange between the fluids, it is common to provide the heat exchangers with a plurality of superimposed fins, each having a generally flat face and perforated with holes for the passage of the tubes in which the internal fluid.

  Still to improve the heat exchange, it is known to deflect or disturb the flow of the external fluid passing through the heat exchanger. To do this, the fins are generally provided with deflectors in the form of a set of longitudinal deflection lamellae arranged parallel to each other and substantially perpendicular to the direction of flow of the external fluid passing through the heat exchanger.

  Different embodiments of heat exchangers of this type are known. Some heat exchangers, for example, have tubes of circular section while others have tubes of oval section. The invention is particularly interested in a heat exchanger in which the perimeter of the holes allowing the passage of the fluid circulation tubes has at least one concave portion opposite a deflector.

  An exemplary embodiment of such a tube is described in document FR 2 722 563.

  The object of the invention is to improve the thermal efficiency of such a heat exchanger. To do this, the invention provides a heat exchanger in which the deflector deflection blades are of length chosen so that the ends of the deflection lamellae delimit a contour of the deflector comprising at least a first convex portion complementary to said concave portion . Thus, the space between the first convex portion of the contour of the baffle and the concave portion of the perimeter of the hole is minimized.

  In a preferred embodiment of the invention, spacers protruding from the surface of the fin are disposed adjacent the deflector, on either side of a central axis of the deflection lamellae. This configuration frees space between one side of the spacer and a tube.

  The baffle advantageously has, at one of its ends at least, a truncated deflection lamella whose length is chosen to be substantially less than the length of an adjacent deflection lamella. This arrangement frees space in the vicinity of the deflection blade.

  In this configuration of the invention, it is advantageous to provide one of the ends of the truncated deflection blade set back with respect to the convex portion of the deflector contour, which makes it possible to transfer all the space freed from same side of the truncated deflection lamella.

  It is then preferable that the length of the truncated deflection blade is chosen so that at least a portion of the base of the spacer element can be accommodated between the end of the truncated deflection lamella and the periphery of the trench. hole for the tube passage facing to reduce the space occupied on the fin by the spacer / baffle assembly.

  A particularly advantageous configuration of the invention provides that the end of the truncated deflection blade has a shape complementary to the shape of the base of the spacer element, the latter preferably having a generally circular base, so to reduce at best the space between this end of the lamella and the spacer element.

  Preferably, the spacer element comprises a raised tab whose surface forms with the direction of flow a chosen angle, preferably close to 20 degrees. Thus, the tab is disposed in the extension of the concave portion of a tube so as not to disturb the flow of the external fluid.

  In a preferred embodiment of the invention, the length of the deflector deflector strips is chosen such that the contour of the deflector has a second convex portion symmetrical to the first convex portion relative to an axis perpendicular to the deflection lamellae. and that the second convex portion is complementary to a concave portion of the periphery of a second hole opposite. The baffle thus has a contour of symmetrical shape with two convex portions and is disposed between two tubes.

  Advantageously, the periphery of the second hole is then of identical shape to the periphery of the first hole and the periphery of the first hole preferably has two concave portions symmetrical with respect to a median axis of the hole. This makes it possible to provide tubes of identical and symmetrical section while maintaining the complementarity of shape between the deflector and the tubes opposite.

  Other features and advantages of the invention will appear on examining the detailed description below, and the accompanying drawings, in which: - Figure 1 is a schematic general representation illustrating both a heat exchanger of the prior art and a heat exchanger according to the invention, comprising cooling fins, - Figure 2 is a schematic representation of a portion of a cooling fin of the heat exchanger of the prior art of the FIG. 2A is a diagrammatic representation of a section of the portion of the cooling fin of FIG. 2 along an axis II-II, FIG. 3 is a diagrammatic representation of a FIG. portion of a cooling fin of the heat exchanger according to the invention of Figure 1 seen from above, - Figure 3A is a schematic representation of a section of the portion of the cooling fin of the figure 3 along an axis III-III; FIG. 4 is a graph comparing the performance of the heat exchanger according to the invention with the performance of the heat exchanger of the prior art; FIG. schematic of a portion of a cooling fin of the heat exchanger according to the invention in a different configuration, and - Figure 5A is a schematic representation of a section of the portion of the cooling fin of the Figure 5 along a VV axis.

  The accompanying drawings may not only serve to complete the invention, but also contribute to its definition, if any.

  Figure 1 schematically illustrates both a heat exchanger of the prior art and a heat exchanger according to the invention.

  The heat exchanger of FIG. 1 comprises, in known manner, two superimposed collecting boxes 2, which are put in communication via at least one series of aligned tubes 4, in which an internal fluid circulates. Between the collector boxes 2 are provided, arranged transversely to the axis of the tubes 4 and parallel to the manifolds 2, fins 6 of substantially rectangular shape whose dimensions in width and in length are substantially equal to those of the manifolds 2. The tubes 4 will be described in more detail

  in the following description.

  The heat exchanger of FIG. 1 can illustrate a heat exchanger of the prior art, which then comprises cooling fins 6 'of the type shown in FIG. 2. The heat exchanger of FIG. 1 can also represent a heat exchanger according to the invention, which is provided with cooling fins 6 "of the type shown in FIG.

  Figure 2 shows, in accordance with the notation conventions described above, a portion of one of the cooling fins 6 'of Figure 1 in the case of a heat exchanger of the prior art. The cooling fin 6 'is in the form of a strip of thin sheet, also called strip, made for example of aluminum alloy, in which is perforated a series of identical holes 8 of similar shape to the section of the tubes 4. The holes 8 are oblong and their periphery has two segments generally parallel to each other whose opposite ends are connected by two semicircles. In addition, the segments of the perimeter of the holes 8 are substantially close to one another in the vicinity of their center, thus giving them a curved shape. Thus, the periphery of a hole 8 has two concave portions symmetrical with respect to the median longitudinal axis of the hole 8. Each of the holes 8 thus allows the passage of a tube 4 through the fin 6 ', the section of the tube 4 being in conformity with the periphery of the hole 8. Such tubes are for example known from the patent FR 94 08819.

  The holes 8 are arranged aligned in an alignment direction parallel to the direction of the length of the cooling fin 6 '. The heat exchanger is provided to be traversed by an external fluid in a flow direction F parallel to the longitudinal axis of the holes 8, that is to say perpendicular to the length of the cooling fin 6 '.

  Between two consecutive holes 8, there is provided a deflector 10 sometimes referred to as the "flow-disrupting element". The deflectors 10 are constructed as a set of identical metal deflection lamellae 12 projecting obliquely from the surface of the fin 6 'as shown in FIG. 2A, which shows a section of the cooling fin 6 of Figure 2 along axis II-II. The deflection blades 12, of generally rectangular shape, are arranged parallel to each other, their ends aligned and their length along the length of the cooling fin 6 '. The deflection blades 12, which are also sometimes referred to as "louvers", are made by a first half-cutting operation of the cooling fin 6 'and then by a folding / stamping operation which forms the lamellae. 12, in particular by inclining them at an angle chosen with respect to the surface of the fin 6 '. The deflection blades 12 are thus formed as deformed portions of the cooling fin 6 '.

  According to this configuration of the deflection lamellae 12, the deflectors 10 have a generally rectangular contour whose long sides are delimited by the ends of the deflection lamellae 12 while the short sides are formed by the long side of the end deflection lamellae 12 . The baffles 10 are arranged such that their length is parallel to the width of the cooling fin 6 '. The deflectors 10 comprise, in the case described here, ten deflection blades 12 equally distributed on either side of the central axis of the cooling fin 6 '. As shown in FIG. 2A, the five deflection blades 12 provided on one side of the central axis of the cooling fin 6 'are inclined with respect to the surface of the cooling fin 6' of an angle selected algebraic while the five deflection blades 12 located on the other side of the central axis are inclined relative to the surface of the cooling fin of an algebraic angle opposite the aforementioned angle.

  The deflectors 10, thanks to the deflection blades 12, deflect the flow F of the external fluid so that it flows in the heat exchanger by participating in the heat transfer with the internal fluid through the tubes 4.

  In each of the spaces delimited by one of the long edges of the cooling fin 6 'and the long side of an end plate of a deflector 10 facing each other, spacers 14 are arranged composed of two raised lugs. 16 protruding from the surface of the fin 6 'at a chosen angle close to 90. The raised legs 16 are provided identical and are in the form of half-disks. The raised tabs 16 are made by cutting and folding a portion of the fin 6 '. The spacer elements 14 are shaped by means of a punch which in a first operation cuts the contour of a circle of desired diameter with the exception of two symmetrical portions and a cutout according to the diameter of said diameter. circle. In a second operation the punch raises the legs thus cut in the cooling fin 6 '. Thus the spacers are circular base.

  The raised lugs 16 are arranged in the direction of the flow F. Once the cooling fins 6 'mounted in the heat exchanger of Figure 1, the ends of the raised lugs 16 opposite the surface of the fin 6' come in support with the fin 6 'more exactly with a lower surface of the fin 6' located above the fin 6 'to which they belong. The raised tabs 16 of the spacers 14 thus act as spacers for maintaining between two superimposed cooling fins 6 'a chosen constant vertical spacing which is also called "pitch".

  At each baffle 10 there are two spacing elements arranged symmetrically with respect to the central axis of the cooling fin 6 ', the center of the basic circular hole of which is located on the median axis of the deflector 10.

  The gaps, that is to say the undeformed portions of the fin, between the edges of the cooling fin 6 'and the spacing elements 16 on the one hand and between the deflection blades 12 of end of a deflector 10 and spacers 16 on the other hand are minimized. This arrangement having only partially satisfied, an object of the present invention is to provide a different configuration of the cooling fin 6 to provide a greater number of cooling fins 12 or a larger width of the deflection lamellae 12 with the intention of improving the heat exchange.

  FIG. 3 illustrates a portion of a cooling fin 6 "which is mounted in a heat exchanger according to the invention illustrated by FIG.

  As previously described, the cooling fin 6 "comprises a series of oblong holes 8 arranged aligned along the length of the fin 6". Between two consecutive holes 8, the cooling fin 6 "is provided with deflectors 30. Like the deflectors 10 of the cooling fin 6 'of FIG. 2, the deflectors 30 are made in the form of metal deflection strips 32, generally rectangular protruding obliquely from the surface of the fin 6 ". The deflection lamellae 32 are arranged parallel to each other and aligned at their center along the width of the fin 6. As with the deflection lamellae 12, the deflection lamellae 32 are produced by semi-cutting the fin 6 ". and then by bending / stamping so that the deflection blades 32 form a chosen angle with the surface of the fin 6 ".The deflection blades 32 are thus formed as part of the cooling fin 6".

  The deflection lamellae 32 of a deflector 30 are arranged equally distributed and symmetrically on either side of the longitudinal central axis of the cooling fin 6. Thus two deflection blades 32 symmetrical with respect to the longitudinal median axis of the cooling fin 6 "are of identical dimensions. As shown in FIG. 3A and in a manner similar to that described above, the deflection blades 32 situated on one side of the median axis of the cooling fin 6 "are oriented with respect to the surface of the the cooling fin 6 "of an algebraic angle while the deflection blades 32 on the other side are oriented at an opposite algebraic angle.

  The deflection blades 32 are of width, that is to say of dimension along the width of the cooling fin 6 "identical but of substantially different length The length of the deflection blades 32 increases from the deflection lamellae 32 closest to the large edges of the deflection fin 6 "to the deflection lamellae 32, one of the long sides of which substantially coincides with the central axis of the cooling fin 6". 32, or small sides, delimit a part of the contour of a deflector 30. The contour of the deflector 30 has, thanks to the different and selected lengths of deflection lamellae 32, two convex portions symmetrical with respect to the median axis The convex portions of a deflector 30 are thus arranged facing the concave portions of the holes 8 located on either side of the deflector 30. The length of the lamellae viation 32 is also selected so that the convex portions of the baffles are of complementary shape to the concave portions of the holes 8. Therefore, a deflector 30 is set to the maximum the space left free between two successive holes 8.

  The end deflection lamellae 32, that is to say the deflection lamellae 32 closest to the edges of the cooling fin 6 "are of length substantially less than the adjacent deflection lamella 32, preferably the length of the end deflection lamellae is close to three quarters of the length of adjacent deflection lamellae 12.

  Each end deflection lamella 12 has a first end coinciding with the contour of the deflector and a second end recessed from the general contour of the deflector 30. The end deflection lamellae 32 have their center offset with respect to the direction The most recessed end of the general contour of the deflector 30 has a quarter-circle shape whose radius of curvature is directed towards the outside of the deflection blade. the most recessed end of the general contour of the deflector 30 and the hole 8 opposite is arranged a spacer 34 similar to the spacer element 14 shown in Figure 2 and described above. In particular, the spacer 34 is of circular base. The quarter-circle shape of the end of the end deflection blade 12 conforms to the circular shape of the base of the spacer element 34 so as to minimize the space between the deflection blade 12 of end and spacing element 34. This configuration of the end deflection lamellae 12 makes it possible to house the spacing elements 34 as close as possible to the deflectors 30 and holes 8 thus ensuring a significant space saving .

  The end deflection lamellae 32 are arranged symmetrically with respect to the center of the deflector 30. Thus, on one of the sides of the central axis of the cooling fin-6 ", the spacing element 34 is disposed on one side of the longitudinal median axis of the deflector 30 while on the other side of the central axis of the cooling fin 6 ", the spacer is provided on the other side of the longitudinal median axis of the deflector 30.

  Unlike the spacer elements 14 described above, the raised tabs 36 of the spacers 34 are oriented with respect to the flow direction F at a selected angle, preferably about 20 degrees. In this configuration, the raised tabs 36 have their surface disposed along the periphery of a hole 8, in its extension, in particular according to the shape of the concave portions of the perimeter of the hole 8.

  The configuration of the cooling fin 6 "placed in the heat exchanger according to the invention makes it possible to gain a maximum of space with respect to the cooling fin 6 'placed in the heat exchanger. of the prior art: A first comparison between the cooling fin 6 'of the prior art and the cooling fin 6 "of the heat exchanger according to the invention indicates that the cooling fin 6" ten deflection lamellae 32, the lengths of which are greater than the length of the deflector fins of the deflectors 10, to which are added two end deflection lamellae 32 of length substantially close to three quarters of the length of a lamella of This configuration of the deflectors 30 makes it possible in particular to increase the heat exchange surface between the inner and outer fluids with respect to the configuration of the deflectors 10 of the prior art. IOR.

  FIG. 4 illustrates the comparative performance of the heat exchanger of the prior art and of the heat exchanger according to the invention.

  FIG. 4 is a graph which represents the power discharged in each of the aforementioned heat exchangers as a function of the speed of the external fluid, in this case air, which passes through the heat exchanger. The measurements were made for different flow rates of the internal fluid respectively 3000, 5000 and 8000 liters per hour and the corresponding results are respectively represented by the curves a, b and c. The curves connecting the squares, that is to say the curves numbered 2, are the curves corresponding to measurements made on the heat exchanger of the prior art while the curves connecting the points, numbered 3, are relative to the measurements carried out on a heat exchanger according to the invention. It is noted that regardless of the flow rate of the internal fluid, the heat exchanger according to the invention allows a significant gain in power dissipated. This evacuated power gain is substantially independent of the air velocity and the internal fluid flow. Tests, not illustrated here, carried out by the Applicant have shown a gain of 2.4% on average in the powers discharged in the heat exchanger according to the invention compared to the powers discharged in the heat exchanger of the prior art. These tests attribute a gain of 0.4% to the configuration of the 36 oriented raised tabs, a 0.4% gain to the deflection lamellae 32 of different lengths and a 1.4% gain to the two deflection lamellae 32. ends. It is noted here that the cumulative area of the deflection blades 32 between two holes 8, that is to say for a deflector 30, is increased by 22.6% between the configuration of the prior art and the configuration according to the invention. invention, without increasing the dimensions of the cooling fin.

  FIG. 5 shows a portion of a cooling fin 6 "'of a heat exchanger according to the invention in a configuration such that the heat exchanger comprises two rows of tubes 4 of the type previously described. heat is commonly referred to as the "two-row heat exchanger" type.

  The cooling fin 6 "'is perforated with two series of oblong holes 8, each oblong hole 8 of a series of holes being disposed aligned by its longitudinal axis with the longitudinal axis of an oblong hole 8 of the second series The two sets of elongate holes 8 are thus symmetrical with respect to the longitudinal median axis of the cooling fin 6 "'. In each series of holes are provided between two oblong holes 8 deflectors 50 to deflect / disturb the flow F of a fluid passing through the heat exchanger.

  The deflectors 50 are similar to the deflectors 30 described above and illustrated in Figure 3. Thus, a deflector 50 comprises a set of deflection blades 32 arranged aligned by their center along the width of the fin 6 "'and parallel to each other. As in the case of a deflector 30 of Figure 3, in a deflector 50 of Figure 5, the deflection blades 32 are of identical width but of selected length so that the ends of the deflection strips 32 delimit two portions convex of the contour of the deflector 50 complementary concave portions of the oblong holes 8 arranged on either side of the deflector 50.

  FIG. 5A schematically represents a section of the portion of the cooling fin 6 "'along a discontinuous V-V axis intersecting two deflectors 50 longitudinally.

  All the deflector fins 32 of a baffle 50 are inclined relative to the surface of the cooling fin 6 "'of a selected algebraic angle, while all deflection fins 32 of the baffle are arranged symmetrically. They are inclined at an angle opposite to the above-mentioned angle, in particular the deflector blades 32 of the deflectors 50 are oriented so that the end of the deflection blades 12 protrude from the surface of the cooling fin. 6 "'is directed towards the large edge of the nearest fin. It is noted here, therefore, that the inclination of the deflection blades 32 is symmetrical with respect to the central axis of the cooling fin 61 ", as in the cases illustrated in FIGS. 2 and 3 and described above, and this, even if the longitudinal median axis of the cooling fin 6 "'passes through neither the deflectors 50 nor the oblong holes 8.

  Unlike a deflector 30 of Figure 3, only the strip located at the end of the deflector 50 closest to the edge of the cooling fin 6 "'is arranged to provide a space capable of accommodating a spacer element 34 of the type described above and illustrated in FIG. 3. The spacer element 34 is in particular arranged as in FIG. 3, that is to say that one of the raised lugs 36 follows substantially the extension of the shape of the concave portion of the oblong hole 8 arranged in the vicinity.The deflection blade 32 of a deflector 50 located closer to the longitudinal central axis of the cooling fin 6 "'is length chosen in such a way that the two ends of this end deflection lamella 32 coincide with the contour of the deflector 50. This end deflection lamella 32 has its center disposed along the longitudinal median axis of the deflector 50 and is longu it is substantially smaller than the length of the adjacent deflection blade 32. This embodiment makes it possible to gain a complete deflection strip 32 at one end of each deflector 50.

  Between two deflectors 50 and aligned along the longitudinal median axis of the cooling fin 6 "'are arranged spacers 14 of the type described above and illustrated in Figure 2. The raised legs 16 of the spacers 14 are arranged along the transverse axis of the cooling fin 6 "', as in the configuration of Figure 2.

  The spacer elements 34 at the ends of two deflectors 50 arranged symmetrically with respect to the central axis of the cooling fin 6 "'are arranged on either side of the longitudinal central axis of the deflectors 50. configuration of the cooling fin 6 "and that of the fin

  6 "'cooling described above can be adapted to different models of heat exchanger, for example heat exchangers with several rows of tubes of the type discussed above or alternatively heat exchangers with tubes of different section.

  Such heat exchangers can be made in particular in the form of a cooling radiator of a motor vehicle engine or a heating radiator of the passenger compartment of a motor vehicle.

  They can also find application in the production of heat exchangers for motor vehicle air conditioning circuits.

  The invention is not limited to the embodiments described above, only as examples, but encompasses all the variants that may be considered by those skilled in the art within the scope of the following claims.

Claims (11)

claims   A heat exchanger comprising a plurality of superimposed fins (6), each having a generally flat and perforated surface of at least a first hole (8) for the passage of a flow tube (4). fluid, the periphery of said hole having at least one concave portion facing a deflector (10,30) in the form of a set of longitudinal deflection lamellae (12,32) arranged parallel to each other and substantially perpendicular to a direction of flow (F) of a fluid passing between the fins (6), characterized in that the deflector blades (32) of the deflector (30) are of selected length so that the ends of the deflection lamellae delimit an outline of the deflector (30) comprising at least a first convex portion complementary to said concave portion.   2. Heat exchanger according to claim 1, characterized in that spacers (34) projecting from the surface of the fin (6) are arranged in the immediate vicinity of the baffle (30), on the one hand and on the other. other of a median axis of the deflector (30).   3. heat exchanger according to one of claims 1 and 2, characterized in that the deflector (30) has, at one of its ends at least, a deflection blade (32) truncated whose length is chosen substan - less than the length of an adjacent deflection lamella (32).   4. Heat exchanger according to claim 3, characterized in that one end of the truncated deflection blade (32) is set back relative to the convex portion of the contour of the deflector (30).   5. Heat exchanger according to claim 4, characterized in that the length of the truncated deflection blade (32) is selected so that at least part of the base of the spacer (34) can be housed between the end of the deflection plate (32) truncated and the periphery of the hole (8) for the tube passage (4) facing.   6. Heat exchanger according to claim 5, characterized in that the end of the deflection blade (32) truncated has a shape complementary to the shape of the base of the spacer element (34).   7. Heat exchanger according to claim 6, characterized in that the spacer element (34) has a generally circular base.   8. Heat exchanger according to one of claims 2 to 7, characterized in that the spacer comprises a raised tab (36) whose surface forms with the direction of flow (F) a chosen angle, preferably neighbor of 20.   9. Heat exchanger according to one of the preceding claims, characterized in that the length of the deflection blades (32) of the deflector (30) is chosen so that the contour of the deflector (30) has a second symmetrical convex portion. the first convex portion with respect to an axis perpendicular to the deflection lamellae (32) and that the second convex portion is complementary to a concave portion of the periphery of a second hole (8) facing.   10. Heat exchanger according to claim 9, characterized in that the periphery of said first hole (8) is identical in shape to the periphery of the second hole (8).   11. Heat exchanger according to claim 10, characterized in that the periphery of the first hole (8) has two concave portions symmetrical with respect to a median axis of the hole (8).