Fluid circulation tube and a heat exchanger comprising such tubes

Abstract

Fluid circulation tube and heat exchanger equipped with tubes of this type are disclosed. The tube (6) is produced by bending, and, once its wall has been bent, has a base portion (12) prolonged laterally by two linking portions (13) leading to two top portions (14) turned toward one another, which terminate in end legs (15) turned toward the base portion (12), forming at least two parallel longitudinal internal channels (16) into which the two systems (20) of bends (21) of a corrugated disrupter (17) can be inserted, these systems being interconnected by a central part (23) inserted into a gap left between said legs and the base portion.

Claims

1. A fluid circulation tube for a heat exchanger the tube comprising a wall defining a base portion and free end legs, turned perpendicularly toward the base portion, a disrupter with bends provided inside the tube, the disrupter having a central portion which is inserted between the end legs and the base portion, parallel to the latter, wherein the central portion of the disrupter has, between at least two adjacent bends, a width equal to a sum of a thicknesses of the free end legs, increased on each side by a safety distance configured for a range of inclinations which the legs assume relative to their nominal position perpendicular to the base portion; wherein the free end legs have crosscut terminal ends and the entirety of the terminal ends are in contact with one face of the central portion, and an opposite face of the central portion is in contact with the base portion; wherein each of the safety distances are parallel to the base portion and equal to a protruded distance of a length of the free end legs, the length of the free end legs measured from the base portion to the terminal end, the free end legs being equal length, said range of inclinations including a first inclination position where both of the free end legs have an inclination of between 20° and 45° in a first lateral direction, and a second inclination position where both of the free end legs have an inclination of between 20° and 45° in a second lateral direction which is opposite the first lateral direction relative to its nominal position perpendicular to the base portion, with side surface of one of the free end legs in contact with side surface of the other of the free end legs and with the 20° and 45° being measured from an opposite side surface of each free end leg.

2. The tube as claimed in claim 1, wherein each safety distance is substantially equal to a projection onto the central portion of the height of the free end leg with an inclination of between 20° and 30° relative to its nominal position perpendicular to said base portion.

3. The tube as claimed in claim 1, wherein said free end legs are adjacent and arranged in a longitudinal plane of symmetry of the bent wall of the tube, forming two identical receiving channels into which said systems of bends, separated by said enlarged central portion, are inserted.

4. The tube as claimed in claim 1, wherein the profile of the bends of the disrupter is sinusoidal.

5. The tube as claimed in claim 1, wherein the profile of the bends of the disrupter is crenellated.

6. The tube as claimed in claim 4, wherein the width of the central portion of the disrupter is between 0.75 and 1.5 times a period of the bends of the disrupter.

7. The tube as claimed in claim 6, wherein the width of the central portion of the disrupter is substantially equal to once the period of the bends of the disrupter.

8. A heat exchanger, comprising at least a plurality of parallel fluid circulation tubes with incorporated disrupters as claimed in claim 1.

9. The heat exchanger as claimed in claim 8, wherein the exchanger forms a condenser of an air conditioning loop for a motor vehicle.

10. The heat exchanger as claimed in claim 9, wherein said free end legs are adjacent and arranged in a longitudinal plane of symmetry of the bent wall of the tube, forming two identical receiving channels into which said systems of bends, separated by said enlarged central portion, are inserted.

11. The tube as claimed in claim 2, wherein said free end legs are adjacent and arranged in a longitudinal plane of symmetry of the bent wall of the tube, forming two identical receiving channels into which said systems of bends, separated by said enlarged central portion, are inserted.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The attached figures will clearly show how the invention can be applied. In these figures, identical references denote similar elements.

(2) FIG. 1 is a schematic view of an air conditioning loop of a vehicle, equipped with a heat exchanger having fluid circulation tubes according to the invention.

(3) FIG. 2 is a cross-sectional view of one of the fluid circulation tubes of the exchanger, with a disrupter having a double system of bends which can be inserted into said tube in an improved way, according to the first aspect of the invention, the cross section being taken in a central portion of the tube.

(4) FIG. 3 is an enlarged detail A of the central portion of the tube of FIG. 2, showing, in a side view, the distance on said central portion which separates the two systems of bends of the double disrupter in order to facilitate the insertion of the latter in the presence of a possible inclination of the end legs of the tube.

(5) FIGS. 4 and 5 are cross sections of a fluid circulation tube of the exchanger, with disrupters composed of single systems of bends and, according to the second aspect of the invention, joint reinforcers which are rounded and right-angled respectively.

(6) FIGS. 4A and 5A are enlarged details A and B respectively of FIGS. 4 and 5, showing, notably, the brazing areas.

(7) FIG. 6 is a cross section of a fluid circulation tube of the exchanger, with a disrupter having a double system of bends and, according to the second aspect of the invention, elbow-shaped joint reinforcers.

(8) FIG. 6A is an enlarged detail C of FIG. 6, showing, notably, the brazing areas.

DETAILED DESCRIPTION

(9) The air conditioning loop or circuit 1 shown schematically in FIG. 1 comprises, in a known way which is described briefly below, in the direction of circulation C of the coolant, a compressor 2, a condenser 3 serving as a heat exchanger, an expansion valve 4 and an evaporator 5. The condenser 3 comprises a bundle of parallel tubes 6, whose ends are connected in a fixed and fluid-tight way to an upstream header box 7 facing the compressor 2, and to a downstream header box 8 facing the expansion valve 4, respectively.

(10) The coolant enters the upstream header box 7 in the vapor phase, then flows through the heat exchange tubes 6 and exits through the downstream header box 8 in the liquid phase, as a result of the external air flow F, which is generally forced, and which flows perpendicularly across the tubes which actively participate in this phase change. The exchanger may also comprise corrugated dividers (not shown) between the tubes, for increasing the air exchange surface area.

(11) For information, depending on the fluid used, the tubes 6 are subject to a pressure of about 20 bar, but must withstand a pressure of 100 bar before bursting.

(12) A tube 6 of this type, shown in FIG. 2, is made by the bending process, in the case with which we are concerned here. It can be seen that this type of tube has a thin wall 10, with a thickness of about 0.2 to 0.5 mm, for example. It is produced by bending in such a way that, generally but not exclusively, it has a cross section in the shape of a flattened B with a longitudinal plane of symmetry P passing perpendicularly between the two loops of the flattened B.

(13) Thus, when the wall 10 has been bent, the tube 6 is composed of a base or median portion 12 which is prolonged laterally by two rounded linking portions 13 and two identical top or upper portions 14 which are coplanar and which are parallel to the base portion 12. The top portions 14, each of which extends over about half the width of the base portion, terminate in adjacent free end legs 15, placed substantially one against the other, which are identical and are bent into a nominal position in which they should theoretically remain after bending and cutting, in other words a perpendicular position, such that they return toward the base portion 12. Thus the rounded portions 13, top portions 14 and legs 15 form, together with the base portion 12, two parallel internal channels or spaces 16, extending over the whole length of the tube 6, which are substantially identical in size in this case, since the adjacent legs are located in the plane of symmetry P of the tube. According to other embodiments, a different bending process could be used to produce more than two channels which may or may not have identical cross sections.

(14) Additionally, a gap e is initially provided between the crosscut edges 19 terminating the free end legs 15 and the internal face 11 of the base portion 12 of the bent wall of the tube, allowing a corrugated disrupter or divider 17 to be inserted.

(15) These disrupters are used in order to improve the thermal performance and the mechanical strength (for withstanding the coolant pressure in the condenser), a disrupter 17 being introduced into the internal channels 16 of the thin wall 10 which has been bent in this way, as shown in FIGS. 2 and 3.

(16) It should be noted that this disrupter 17 is produced from a thin sheet of metal which, in this case, is worked into a sinusoidal corrugated shape with two systems 20 of parallel bends 21, the peaks 22 of the bends 21 touching the internal face 11 of the bent wall 10 and extending in a parallel manner along the tube 6, these systems being interconnected by a flat central portion 23. The disrupter 17 is fitted in the tube 6 by engaging and then sliding the two systems 20 of corrugated bends 21 and the flat central portion 23, respectively, into the two internal channels 16 and into the gap e between the edges 19 of the legs 15 and the base portion 12. The thickness of the disrupter is, for example, about 0.05 to 0.150 mm. In order to simplify the fitting process, provision may be made to insert the disrupter when the tube has a clearance of more than e, and then to perform a rolling operation on the assembly to complete the bending of the tube, notably by bringing the disrupter and the legs into contact with the tube walls.

(17) In the nominal condition, in other words at a distance from the ends of the tube or at said ends if the cutting has not caused the deflection of the legs 15, the ends 19 of said legs 15 are in contact, notably by their crosscut edges, with one of the faces of the central portion 23 of the disrupter. The other face of the central portion 23 of the disrupter is in contact with the base portion (12) of the tube.

(18) The further assembly of the disrupter 17 and the tube 6 is usually carried out by brazing in a furnace, using claddings which are not shown, deposited on the internal face of the bent wall of the tube and/or on the corrugated faces of the double disrupter.

(19) According to the first aspect of the invention, in order to allow the disrupter 17 to be introduced easily into the tube 6 without any risk of damage to these components, the flat central linking portion 23 of the disrupter is enlarged so as to have a width L considerably greater than the sum of the thicknesses E of the two adjacent free end legs 15, which is equal to twice the thickness of the bent wall forming the tube 6. This is done in order to allow for any inclination or deflection of the adjacent legs 15 which may occur for the aforementioned reasons, although the legs should occupy a nominal position, after bending and cutting, which is substantially perpendicular to the base portion 12, in the plane of symmetry P, as shown in FIG. 2.

(20) Thus, safety distances D shown in FIGS. 2 and 3 are added to the sum of the thicknesses E of the juxtaposed legs 15, one on each side of these legs, when the legs are in the initial perpendicular position, the aim being to allow for an acceptable range of inclinations which the legs may assume after the cutting operation relative to their nominal position perpendicular to the base portion 12.

(21) A maximum inclination of the legs would be one in which they were bent back completely onto the internal faces 11 of the top portions 14, in such a way that each safety distance D would be substantially equal to the height H of the legs. A more reasonable estimate of this safety distance D corresponds to an inclination of not more than 45°, and generally less than 20°-30° on either side of the longitudinal plane of symmetry P, in other words the nominal vertical position of the legs in FIGS. 2 and 3. This results in a safety distance D equal to the projection, onto the central linking portion 23, of the height H inclined at a maximum of 45°, in other words H/√2, or less if it is desired to limit the distance D to a smaller possible inclination of the legs.

(22) The deflected positions which the entry edges of the legs 15 may assume, on either side of the plane P, are shown in broken lines in FIG. 3.

(23) Thus the width of the flat central portion 23, separating the two systems 21 of corrugated bends 22, is substantially equal to 2(E+D), as is shown more fully in FIG. 3. Clearly, this estimate of the safety distance could be refined, reduced or increased without departure from the principle of the invention, which is that of having a sufficiently wide central linking portion 23 to enable the systems of bends of the disrupter 17 to be inserted without difficulty into the receiving channels 16 of the tube 6, even if the entry edges of the adjacent legs 15 are deflected to some extent.

(24) It should also be noted that the extension of the width L of the central portion 23 must not be provided at the expense of the number of bends 21, which must remain acceptable in order to maintain the heat exchange and the mechanical strength of the tube. It can be seen in FIGS. 2 and 3 that, at the end of the process, the bends of the systems facing the legs are close to the latter, without compromising the integrity of the tube; on the other hand, the bends 25 facing the rounded linking portions 13 have a profile which mates with the latter portions.

(25) A bend of the disrupter 17 which is, for example, identical to the other bends of the disrupter, originates on each side of the central portion 23.

(26) In this case also, according to the second aspect of the invention, illustrated in the subsequent figures, there is a tube 6, shown in cross section in FIGS. 4 to 6, having the same characteristics as the tube 6 described previously in relation to the preceding aspect of the invention.

(27) Accordingly, in FIGS. 4 and 5, two disrupters 17 are introduced into the internal channels 16 of the thin wall 10 bent as described, in place of the single disrupter 17 described in relation to FIG. 2. These disrupters 17 are substantially identical and are usually produced from a thin sheet of metal which is worked, in this case, into a sinusoidal corrugated shape with a single system of bends 21, in such a way that the peaks 20 of the parallel bends 21 touch the internal face 11 of the bent wall 10 and extend in a parallel manner along the tube 6. Like the single disrupter 17 of the preceding aspect of the invention, these two disrupters 17 serve to improve the thermal performance and the mechanical strength (for withstanding the coolant pressure in the condenser).

(28) Accordingly, one terminal bend 22′ of each disrupter 17 is substantially in contact with the corresponding end leg 15, and the other terminal bend 23′ substantially faces the rounded linking portion 13 of the tube 6.

(29) The materials used for the thin wall 10 and the disrupters 17 are generally identical aluminum alloys, and claddings (not shown) are deposited on them (the thin wall and the disrupters) for the purpose of subsequent brazing in a furnace.

(30) As shown in FIGS. 4-4A and 5-5A, the adjacent legs 15 of the thin wall 10 extend until their crosscut edges 19 are substantially in contact with the internal face 11 of the base portion 12.

(31) According to the second aspect of the invention, the terminal bends 22′ of the disrupters 17 housed in the longitudinal channels 16 also come into contact, substantially, with the end legs 15 and with the base portion 12 in question, thereby forming a joint reinforcer 24′ between the end legs 15 and the base portion 12.

(32) In the example shown in FIGS. 4 and 4A, each terminal bend 22′ forming the joint reinforcer 24′ has a rounded fillet shape 25′ corresponding in a simple way to the start of the sinusoidal profile, and extending between the free end leg 15 and the base portion 12. The longitudinal free edge 26′ of the fillet 25′ is located, for example, at least a third of the way up the leg from its edge, thus ensuring correct longitudinal support, and the rounded shape of the fillet, together with the leg and the base portion which are perpendicular to each other, delimits a longitudinal clearance or empty space 27′.

(33) Thus each terminal reinforcing bend 22′ is fixed to the leg 15 and the base portion 12 by brazing, when the assembled condenser (including the tubes with the incorporated disrupters and the header boxes) is placed in the furnace provided for this purpose. In a known way, claddings (not shown) for use in brazing are deposited over all or part of the two corrugated faces of the disrupter and/or on the internal face of the bent wall forming the tube. Thus, by arranging the terminal bend 22′ in the angle formed by each leg with the base portion, effects of capillarity and wettability are created when the deposited brazing compound changes from the solid state to the liquid state, in which it tends to flow and accumulate around the reinforcer 24′, thus being present on both sides of the peak 20 of the rounded fillet 25′, while also filling the clearance 27′ between this rounded reinforcing fillet 24′, the leg 15 and the base portion 12, and on the free edge 26′ of the fillet. The resulting brazing areas or seams are indicated by ZB in FIG. 4A and clearly show how each leg 15 is fixed by brazing to the base portion 12 with the aid of the terminal bend 22′ of the disrupter 17 which acts as a reinforcer 24′.

(34) It can be seen, therefore, that the two initially free adjacent end legs 15 are held in a sandwich formation by the reinforcing bends which are brazed along their whole length to the legs and the base portion, thus ensuring the mechanical strength of the tubes 6 even at high pressures.

(35) In the embodiment shown in FIGS. 5 and 5A, the terminal bend 22′ of each disrupter 17 is bent to form a right angle. Thus, a first limb 28′ of the bend is parallel to the leg 15 and is applied against it from its crosscut edge 19 to about one third of the way up the leg, and a second flat limb 29′, bent at 90° to the first limb 28′, is applied against the corresponding base portion 12. This second limb 29′ is then prolonged in the usual way in a sinusoidal shape, the peaks 20 being applied, alternately, against the internal faces 11 of the base wall 12 and the top portion 14 in question.

(36) These terminal bends 22′, in the form of L-section angle pieces, constitute bent joint reinforcers 24′ which fix the initially free adjacent end legs 15 as a result of brazing to the base portion 12 of the tube. In FIG. 5A, the brazing areas ZB are indicated, these areas being produced, notably, by large deposits on the free edge 30 of the first limb 28′ where it meets the leg 15, and at the change of angle between the second limb 29′ and the base portion 12. The brazing area ZB also extends, although with reduced thickness, between the contact surfaces of the limbs 28′, 29′ and the corresponding surfaces of the legs 15 and the base portion 12.

(37) Instead of using two disrupters 17 with single identical systems of bends in the two longitudinal channels 16 of the tube 6, it is possible, in certain cases, to use only a double disrupter 40′ having two separate parallel systems 31′ of corrugated bends 32′, of the type described in relation to the first aspect of the invention.

(38) In this case, as shown in FIGS. 6 and 6A, the crosscut sections 19 terminating the adjacent end legs 15 of the bent tube 6 are at a distance from the internal face 11 of the base portion 12. In this case, the gap is substantially equal to the wall thickness e of the disrupter 40′ and is, notably, equal to the flat central linking portion 34′ of the disrupter which joins the two identical systems 31′ of corrugated bends 32′. Thus, the one-piece disrupter 40′ with two systems of bends 31′ can be introduced by engaging the central linking portion 34′ in the gap left between the edges 19 of the legs 15 and the internal face 11 of the base portion 12 of the tube 6. The two systems 31′ engage simultaneously and completely in the oblong channels 16, as before, with the peaks 35′ of the bends 32′ interacting with the internal face 11 of the base portion 12 and the top portions 14 in question.

(39) For the purpose of fixing the initially free legs 15, the bends forming the joint reinforcers 24′ according to the invention are considered to be the first terminal bends 36′ of the systems originating from the central portion 34′ and turned toward the legs, as opposed to the last terminal bends 37′ which are turned toward the linking portions 13. These first reinforcing bends 36′ are bent at the point of the outer corners 38′ of the edges 19, and are partially formed by the flat central area 34′ and by the lateral prolongations 39′ originating therefrom, which extend toward the respective top portions 14 and progressively depart from the end legs. The inclination imparted to these lateral prolongations 39′ of the first bends 36′ used as joint reinforcers 24′ is reproduced in the shape of the corrugations of the two systems 31′ of bends which, in the example shown in FIGS. 6 and 6A, is of the crenellated type, notably with trapezoidal crenellations. Any other appropriate shape, such as square or even sinusoidal, would also be feasible.

(40) These first reinforcing bends 36′ stiffen the bent tube 6 by means of the brazing areas ZB which are, notably, produced by the usual claddings, in the angle formed by each corner 38′ between the leg 15 and the inclined prolongation 39′ on the one hand, and in the angle between the inclined prolongation 39′ and the base portion 12 on the other hand.

(41) As shown in FIG. 6, the width of the central linking portion 34′ is substantially equal to the sum of the thicknesses of the two adjacent legs 15. The placing of the terminal bends forming joint reinforcers on the disrupters at the point where the free ends of the legs meet the base portion of the wall causes the mechanical strength of the tube to be maintained, even under high pressure, owing to the large brazing seams which tend to be deposited in considerable amounts, notably by the capillary effect, along the terminal bends which are applied against the legs and the base portion of the tube.