FR2851815A1 - Collector box for pressure-resistant heat exchanger used in motor vehicle air conditioning, uses crenellated plates brazed to walls of collector, to provide structural strength against high internal pressures while assisting heat transfer - Google Patents

Abstract

The collector box (2) of a heat exchanger (1) houses a number of reinforcing plates (20) brazed to the walls of the exchanger. The reinforcing plates are laminated and folded to a crenellated profile. The crenellations profiles of two adjacent laminations are mutually offset in the longitudinal direction to form passages (44) connecting adjacent spaces to the two faces of the plates.

Description

VCL1439.FRD

  The invention relates to a manifold for a heat exchanger, intended in particular to be traversed by a refrigerant in an air conditioning installation of a motor vehicle.

  FR 2 793 016 A describes such a manifold, comprising: a) a first wall defining a manifold plate and having openings intended to allow fluid communication between the interior of the manifold and a bundle of tubes of the heat exchanger; b) a second wall opposite the first, defining a bottom; the first and second walls delimiting between them at least one fluid chamber communicating with at least one subset of the tubes; and c) a reinforcement housed inside each fluid chamber, formed by a sheet of a thickness less than the free distance between said first and second walls, shaped so as to present with each of these latter brazing connection zones distributed in a dense manner substantially over the entire surface of the fluid chamber, and having cutouts to allow proper circulation of fluid in the latter. 30 In the air conditioning installations of motor vehicles, refrigerants are now used which, such as CO 2, induce very high pressures, of the order of 100 bars in operation and 350 100 bars during the burst tests. The reinforcement described in the aforementioned document allows the manifold to withstand high internal pressures without damage, while maintaining the usual wall thicknesses in air conditioning exchangers. It is corrugated according to a profile similar to a sinusode, its corrugation crests extending substantially in a straight line over its entire width and forming zones of continuous connection with said walls, and said cutouts are formed in the sides of the corrugations. These cutouts 5 allow the fluid to pass through the corrugated reinforcement and therefore to circulate throughout the volume of the chamber. The opening rate of the cutouts is however limited, under penalty of mechanically weakening the reinforcement and consequently compromising its function, which slows down the circulation of the fluid, and leads to a less good distribution of the latter in the channels. tubes, as well as pressure drops which deteriorate performance.

  The object of the invention is to remedy this drawback. The invention relates in particular to a manifold of the kind defined in the introduction, and provides that said cutouts are made in the form of slots oriented and aligned along lines parallel to a first direction, delimiting between them strips of material each of which is folded according to a crenellated profile, the slots of the profiles of two adjacent strips being mutually offset in the first direction so as to form transverse passages relative thereto, each connecting two adjacent spaces 25 respectively to the two faces of the sheet.

  Optional, complementary or alternative characteristics of the invention are set out below: - Said free distance is delimited by a substantially planar internal face of the first wall extending substantially over the entire surface of the fluid chamber.

  - The first wall has collars intended to surround said tubes, facing outwards from the manifold.

  - The first wall has collars intended to surround said tubes, turned towards the interior of the collecting box and whose free ends delimit said free distance and form connection zones with the reinforcement.

  - The slots are substantially rectangular.

  - The slots have substantially the shape of isosceles trapezoids.

  - The reinforcement has in a second direction perpendicular to the first direction a periodic structure with a pitch equal to the width of n consecutive bands, n being an integer greater than 1, n vertices of slots belonging to n consecutive bands having a portion of common length by which they connect directly to each other, and n niche slots belonging to n consecutive bands having a portion of common length through which they connect directly to each other.

- n is chosen from 2 and 3.

  - The first and second walls define at least two fluid chambers, the fluid chambers being separated from each other by at least one partition. 25 - Each partition is constituted by a projection formed on the second wall.

  - The first wall has at least one row of openings 30 mutually aligned in a longitudinal direction.

  - The second direction is substantially parallel to said longitudinal direction.

  The first and second walls delimit at least two fluid chambers, the fluid chambers being distributed over two rows each comprising at least one chamber, respectively disposed on either side of a partition extending in said longitudinal direction, and the first wall has a row of openings for receiving flat tubes, each communicating with two chambers belonging respectively to the two rows of chambers.

  - At least one of said rows of chambers comprises at least two chambers, two adjoining chambers of the same row being separated from each other by a transverse partition.

  The invention also relates to a heat exchanger, in particular for a refrigerant in an air conditioning installation of a motor vehicle, comprising at least one manifold as defined above, and a bundle of tubes, each tube communicating by a first of its ends with one of the openings of the collector plate.

  The heat exchanger according to the invention may include at least some of the following features: - The tubes are flat in shape and each have a multiplicity of parallel channels for independent circulation of fluid.

  - Two subsets of the channels of each tube communicate respectively with the two corresponding chambers.

  The channels of the two sub-assemblies communicate, at the second end of the tube, with a common space for carrying out a U-shaped fluid circulation in the tube from one chamber to another.

  The characteristics and advantages of the invention are explained in more detail in the description below, with reference to the accompanying drawings.

  Figure 1 is a partial view in longitudinal section of an evaporator according to the invention for a motor vehicle air conditioning loop using Ca2 as the refrigerant.

  FIG. 2 is a partial sectional view along the line IIII in FIG. 1.

  Figure 3 is a partial view similar to Figure 2, relating to a variant of the evaporator.

  FIG. 4 is a partial sectional view along line IVIV of FIG. 1.

  FIG. 5 is a view similar to FIG. 4, relating to the variant of FIG. 3.

  FIG. 6 is a partial perspective view of the manifold plate of the evaporator shown in FIGS. 3 and 15 5.

  Figure 7 is a perspective view of the evaporator of Figures 1, 2 and 4, the cover of the manifold being removed to reveal the reinforcements. Figure 7a is an enlarged detail of Figure 7.

  FIG. 8 is a cross-sectional view of a variant of the manifold cover shown in FIGS. 2 to 5.

  FIG. 9 is a partial view in cross section of a reinforcement which can be used in replacement of those shown in FIGS. 2 to 5 and 7.

  The evaporator 1 shown in Figures 1, 2 and 4 comprises in known manner a manifold 2 formed essentially by a hollow part 3 in the form of a bowl and a cover 4 closing the latter. The part 3, which acts as a collecting plate, has a flat bottom wall 5 and a peripheral edge 6. The wall 5 is pierced with a row of narrow openings 7, the largest dimension of which extends over most of the width of the box. The cover 4 also includes a flat wall 8 which extends opposite the wall 5, parallel to the latter, as well as two lateral edges 9 and a middle rib 10 elongated in the longitudinal direction of the box, extending towards the wall 5 from the wall 8. The parts 2 and 3 are 5 brazed together so as to delimit between them two chambers II and 12 for the fluid, located respectively on either side of the rib 10. A connection d fluid inlet and outlet 13 allows communication between the chambers 11 and 12 and the rest of the loop. This connector is made up of several pieces brazed together and to pieces 3 and 4. Its structure is foreign to the present invention and will not be described in detail.

  The evaporator further comprises a row of flat tubes 14, 15 one end of each tube engaging an opening 7 in the wall 5, while the opposite end of the tube is capped by a cover 15. Each tube 14 is pierced with a multiplicity of longitudinal channels 16, some of which denoted 16-1 communicate with the chamber 11 and others denoted 16-2 20 with the chamber 12, all the channels also opening into the internal space 17 of the cover 15 The channels 16 of the different tubes therefore define parallel U-shaped paths between the chambers 11 and 12, through the spaces 17.

  The wall 5 forms around the openings 7 collars 18 which project towards the outside of the manifold.

  According to the invention, each of the chambers 11 and 12 contains a reinforcement 20 brazed to the walls 5 and 8 so as to maintain the distance between them and to avoid swelling of the manifold under the effect of the high pressures at which it is subjected by the refrigerant. The reinforcement 20 is formed from a metal sheet in which slots are provided with practically no removal of material, after which the sheet is folded so as to separate the two edges of each slot from each other. The slots extend in segments belonging to straight lines parallel to a direction D1, and equidistant, several slots being aligned on the same straight line. These straight lines delimit between them strips of material of equal width which, after folding the sheet, as can be seen particularly in FIGS. 2, 4, 7 and 7a, extend according to a profile in 5 substantially rectangular slots, the slots of each strip being offset in the direction D1 (which here corresponds to the transverse direction of the chambers 11, 12, of the manifold and of the exchanger), relative to those of the adjacent strips. Thus, the same strip provides (FIG. 7a) two 10 vertices of consecutive slots 21 and 22, mutually aligned in the transverse direction of the manifold, between which a bottom of slot 23 is interposed. The bottom 23 is connected to the top 21 by a niche side 24 and at the top 22 by a niche side facing the rear of the figure, facing the side 24. The strip located immediately to the right of the previous form of niche summits 25 and 26, a bottom of slot 27, a side of slot 28 and a side of slot facing the latter, which are offset by a length d towards the rear of the figure relative to the slots of the first strip mentioned above. The second strip is followed by a third strip defining peaks of slots 29 and 30, a slot bottom 31, a slot flank 32 and a slot flank opposite to it which are offset with respect to the preceding slots 25 by example of the same distance d. The next strip defines niche peaks 33 and 34, a niche bottom 35, a niche side 36 and a niche bottom opposite to it which are offset in the example by a distance 2d towards the front of the figure with respect to the previous 30 slots, and therefore aligned in the longitudinal direction of the chamber with the slots of the first strip. The arrangement of the slots of the first three strips is repeated over the entire length of the fluid chamber, defining a periodic structure whose pitch is equal to three times the width of a strip.

  Each slot top and each slot bottom have a length 1 in the direction of the strips, that is to say in the transverse direction of the exchanger, which is greater than 2d in the example described, such so that the vertices 22, 26 and 30, for example, and the corresponding vertices belonging to the other sequences of three bands, all connect with each other, without discontinuity, in the plane which contains them.

  Each edge of a slot defines an edge of a niche flank and an edge of a vertex or a niche bottom adjacent to it. Thus, for example, an edge of a slot defines the edges 40 and 41, turned to the left of FIG. 7a, of the apex 33 and of the flank 36 respectively, and the opposite edge of the same slot defines the edges 42 and 43 , turned to the right of the figure, bottom 31 and side 32 respectively. The slot thus deployed forms an opening 44 which allows the circulation of the fluid, preferably in the longitudinal direction of the chamber, between the spaces located above and below the reinforcement 20, the fluid thus being able to circulate under the reinforcement to enter the channels of the tubes via the collars. The set of peaks of the 20 slots formed by the reinforcement is brazed to the internal face of the wall 8 and the set of slot bottoms is brazed to the internal face of the wall 5.

  The evaporator partially shown in Figures 3, 5 and 25 differs from that described above in that the collars 18 surrounding the tubes 14 are turned inward and not outward of the manifold. The bottoms of the reinforcement slots are therefore brazed on the ends of these collars and no longer on the continuous flat surface 30 of the manifold. The ends of the collars nevertheless have contact zones with the reinforcement distributed in a sufficiently dense manner to ensure a solid connection by brazing.

  FIG. 8 represents a variant of the cover 4 of the manifold, in the form of a stamped sheet. The rib 10 separating the two chambers is obtained by a U-shaped folding. FIG. 9 represents an insert 20 which differs from that described previously in that the profile of the slots is substantially trapezoidal instead of being substantially rectangular, and that the pitch of the periodic structure in the longitudinal direction is twice, not three times the width of a strip. Thus, the strip traversed by the cutting plane has peaks of slots 50, bottoms of slots 51, flanks of inclined slots 52 turned to the left of the figure and flanks of inclined slots 53 turned to the right. The adjacent strip, behind the plane of the figure, has peaks of slots 54, bottoms of slots 55, flanks of slots 56 turned to the left and flanks of slots 57 turned to the right, which are offset towards the straight with a length d relative to the slots of the first strip, d being less than the length 1 of the peaks of slots and the bottoms of slots. The slots formed by the other bands of the reinforcement are aligned perpendicular to the plane of the figure, alternately with those of the first band and with those of the second band.

  The above description has no limiting character as to the structure of the reinforcement according to the invention. The slots can have a different shape from that of a rectangle 25 and an isosceles trapezoid. The reinforcement may have a periodic structure with a pitch equal to the width of more than three consecutive bands. This structure can also not be periodic, and in particular be defined randomly. In the embodiments described, the mutual offset of the slots of any two strips of a reinforcement has either the value 0, or a value d, or even, only in the case of the reinforcements of FIGS. 2 to 5 and 7, the value 2d, that is to say in all cases an integer multiple of a fixed value d. However, it is possible according to the invention to provide offset values which are not multiple from one another. The width of the bands can also vary from one band to another.

  Similarly, the manifold can have more than two fluid chambers each containing a reinforcement, the chambers belonging to the same row being separated from each other by transverse partitions. The number of passes 5 made by the fluid is determined by the number of chambers; it is 2 in the examples described. It is also possible to provide a single chamber per box for circulation in a single pass between two manifolds fitted respectively with fluid inlet and outlet connections, thus defining an I-circulation exchanger.

Claims (18)

claims   1. Collector box (2) for a heat exchanger, intended in particular to be traversed by a coolant 5 in an air conditioning installation of a motor vehicle, comprising: a) a first wall defining a collector plate (5) and having openings ( 7) intended to allow fluid communication between the interior of the manifold and a bundle of tubes (14) of the heat exchanger; b) a second wall opposite the first, defining a bottom (8); the first and second walls (5, 8) delimiting between them at least one fluid chamber (11, 12) communicating with at least one subset of the tubes (14); and c) a reinforcement (20) housed inside each fluid chamber (11, 12), formed by a sheet of a thickness less than the free distance (e) between said first and 20 second walls (5, 8), shaped so as to present with each of the latter brazing connection zones distributed densely over substantially the entire surface of the fluid chamber (11, 12), and having cutouts (40-43) to allow proper fluid circulation therein, characterized in that said cutouts are made in the form of slots (40-43) oriented and aligned along lines parallel to a first direction (Dl), delimiting between them bands of material, each of which is folded according to a crenellated profile, the slots (21, 24, 23, 25, 28, 27) of the profiles of two adjacent strips being mutually offset in the first direction (Dl) so as to form passages ( 44) transverse x relative thereto, each connecting two spaces respectively adjacent to the two faces of the sheet.   2. Collector box according to claim 1, in which said free distance (e) is delimited by a substantially planar internal face of the first wall (5) extending substantially over the entire surface of the fluid chamber (11, 12).   3. Collector box according to claim 2, in which the first wall (5) has collars (18) intended to surround said tubes (14), turned towards the outside of the collector box.   4. Collector box according to claim 1, in which the first wall (5) has collars (18) intended to surround said tubes, turned towards the inside of the collector box and whose free ends delimit said free distance (e ) and form connection zones with the reinforcement.   5. Collector box according to one of the preceding claims, in which the slots (21, 24, 23, 22) are substantially rectangular.   6. Collector box according to one of claims 1 to 4, in which the slots (53, 50, 51, 52) have substantially the shape of isosceles trapezoids.   7. Collector box according to one of the preceding claims, in which the reinforcement (20) has in a second direction (D2) perpendicular to the first direction (Dl) a periodic structure with a pitch equal to the width of n strips consecutive, n being an integer greater than 1, n vertices of slots (21, 25, 29) belonging to n 30 consecutive bands having a portion of common length by which they are connected directly to each other, and n bottoms of slots (23 , 27, 31) belonging to n consecutive bands having a portion of common length by which they are connected directly to each other. 35 8. Collector box according to claim 7, in which n is chosen from 2 and 3.   9. Collector box according to one of the preceding claims, in which the first and second walls (5, 8) delimit at least two fluid chambers (11, 12), the fluid chambers being separated from each other by at least a partition (10).   10. Collector box according to claim 9, in which each partition is constituted by a projection (10) formed on the second wall.   11. Collector box according to one of the preceding claims, wherein the first wall has at least one row of openings (7) mutually aligned in a longitudinal direction.   12. Collector box according to claim 11, in which the second direction (D2) is substantially parallel to said longitudinal direction.   13. Collector box according to one of claims 11 and 12, wherein the first and second walls (5, 8) delimit at least two fluid chambers (11, 12), the fluid chambers being distributed in two rows each comprising at least one chamber, respectively arranged on either side of a partition (10) extending in said longitudinal direction, and the first wall has a row of openings (7) for receiving flat tubes, each communicating with two chambers (11, 12) belonging respectively to the two rows of chambers. 30 14. Collector box according to claim 13, in which at least one of said rows of chambers comprises at least two chambers, two adjacent chambers of the same row being separated from each other by a transverse partition.   15. heat changer (1), in particular for a refrigerant in an air conditioning installation of a motor vehicle, comprising at least one collecting box (2) according to one of the preceding claims, and a bundle of tubes (14) , each tube communicating by a first of its ends with at least one of the openings (7) of the collecting plate (5).   16. A heat changer according to claim 15, wherein the tubes are flat in shape and each have a multiplicity of parallel channels (16) for independent circulation of fluid.   17. heat changer according to claim 16 comprising a manifold according to claim 13, in which two sub-assemblies (16-1, 16-2) of the channels (16) of each tube (14) communicate respectively with the two 15 corresponding chambers (11, 12).   18. heat changer according to claim 17, in which the channels (16) of the two subassemblies (16-1, 16-2) communicate, at the second end of the tube, with a common space (17) to make a U-shaped fluid circulation in the tube from one chamber to another.