FR3125583A1 - Advanced disturbance elements for improving the performance of low temperature radiator tubes - Google Patents

Abstract

The present invention relates to a tube (2) for a heat exchanger (1) defining a fluid circulation channel (100), comprising a first planar wall (3), comprising at least one disturbance element (10) present on this first plane wall (3), in the fluid circulation channel (100), so as to disturb the flow of this fluid, the disturbance element (10) comprising in particular a local deformation of this first plane wall (3) of the tube (2) towards the inside of the tube (2), the disturbance element (10) comprising a crest (20) having the shape of a chevron, comprising two branches (12, 13) joining together at a vertex ( 11), the ratio of the width l of the disturbance element (10) to the width L of the first flat wall (3) is between 0.6 and 1.0, in particular between 0.7 and 0.9 . Abstract Figure: Figure 2

Description

Advanced disturbance elements for improving the performance of low temperature radiator tubes

The field of the present invention is that of heat exchangers, in particular intended to equip the air conditioning loops of motor vehicles or to cool the engine of a vehicle.

The heat exchangers fitted in particular to the air conditioning loops of vehicles are arranged to allow the adjacent circulation in two separate spaces of two different fluids, so as to carry out a heat exchange between the fluids without mixing them. A type of heat exchanger used among others in the automotive field is the tube exchanger, the exchanger being made up of a stack of tubes brazed together and arranged to define the spaces where the fluids circulate. Within the heat exchangers and the thermodynamic circuits to which they are attached, the fluids circulate by dissipating or absorbing thermal energy.

The efficiency of heat exchangers and thermodynamic circuits is mainly determined by the heat exchanges between the fluids flowing through them. The design of heat exchangers in which the heat exchanges between the fluids circulating within them are optimized is therefore sought. For this purpose, it is possible in particular to aim for a mixing of each fluid within the space in which this fluid circulates, with the aim of increasing the heat exchanges between the fluids, and it is known to equip the heat exchangers with fluid flow disturbance elements.

We understand that to increase the mixing of fluids, it is possible to increase the number of disturbance elements and we can thus seek to bring them closer to each other. But this solution, if it makes it possible to improve the mixing and the quantity of heat exchange, does not respond satisfactorily to the problem mentioned of optimizing the heat exchanges because the multiplication of the disturbance elements causes a significant pressure drop which limits the circulation of fluids and therefore the efficiency of the heat exchanger.

The object of the present invention is therefore to solve the drawbacks described above by designing a tube for a heat exchanger arranged to improve the heat exchange between the fluids flowing through the heat exchanger, in particular by limiting the pressure drops suffered by these fluids.

More particularly, the invention relates to a tube for a heat exchanger defining a fluid circulation channel, this channel comprising a first flat wall, comprising at least one disturbance element present on this first flat wall, in the fluid circulation channel , so as to disturb the flow of this fluid. The disturbance element comprises in particular a local deformation of this first planar wall of the tube towards the inside of the tube, the disturbance element comprising a crest having the shape of a chevron, comprising two branches joining together at a vertex, the ratio of the width l of the disturbance element to the width L of the first plane wall is between 0.6 and 1.0, in particular between 0.7 and 0.9, ideally of the order of 0.8 .

According to one of the aspects of the invention, the fluid circulation channel has a longitudinal direction, the length of this tube being defined in the longitudinal direction.

According to one of the aspects of the invention, the crest of the disturbance element comprises a first free end and a second free end between which the disturbance element extends. The disturbance element is formed by two branches each starting from one of the free ends, these two branches joining together at a vertex.

According to one of the aspects of the invention, the ridge is contained in a plane parallel to the first planar wall, in other words, the altitude of the ridge relative to the first planar wall is substantially constant all along this ridge.

According to one of the aspects of the invention, the two branches forming the disturbance element are symmetrical to each other with respect to a plane of symmetry S, which plane S passes through the vertex of said disturbance element and is defined both by the longitudinal direction of the fluid circulation channel and by a direction perpendicular to the first planar wall.

According to one of the aspects of the invention, the width l of the disturbance element is defined as the distance between the first free end and the second free end of the crest of the disturbance element.

According to one of the aspects of the invention, the first planar wall comprises a first internal face facing the fluid circulation channel, this first internal face having a width L measured in a direction perpendicular to the plane S.

According to one of the aspects of the invention, the tube comprises a second planar wall extending in the longitudinal direction, this second planar wall being parallel to the first planar wall, this second planar wall comprising a second internal face facing the channel.

According to one of the aspects of the invention, the tube has a ratio of the height h of the disturbance elements to the height H of the channel is between 0.1 and 0.4, in particular between 0.2 and 0.3.

According to one of the aspects of the invention, the height h of the disturbance elements is the distance between the first internal face and the crest of the disturbance element, a distance defined in a direction perpendicular to the first planar wall.

According to one aspect of the invention, the height H of the channel is the distance between the first internal face and the second internal face, defined in a direction perpendicular to the first planar wall.

According to one of the aspects of the invention, the height h of the disturbance elements is between 0.1 and 0.6 mm, in particular between 0.2 and 0.5 mm, ideally 0.325 mm.

According to one aspect of the invention, the ratio of the height h of the disturbance elements to the thickness e of the first flat wall (4) is between 0.1 and 4.0, in particular between 0.5 and 2, 5.

According to one of the aspects of the invention, the first planar wall comprises a first outer face facing the outside of the tube, e being the thickness of the first planar wall, measured in a direction perpendicular to the first planar wall between the first internal face and the first external face.

According to one of the aspects of the invention, the branches forming the chevron form between them an angle of between 100° and 140°, in particular between 110° and 130°, ideally 120°.

According to one of the aspects of the invention, the tube comprises additional disturbance elements, in addition to the disturbance elements, and the crest of which has a shape different from the crest of the disturbance elements, whether it is a chevron shape of different size, round, rectangular or oval for example, these shapes not being limiting.

According to one of the aspects of the invention, the tube comprises additional disturbance elements, in addition to the disturbance elements, the number of additional disturbance elements aligned along a direction perpendicular to the longitudinal direction and extending along the width L of the first planar wall is greater than one.

According to one of the aspects of the invention, the additional disturbance elements are inserted between two disturbance elements. In other words, along the longitudinal direction, each additional disturbance element, or each pair of additional disturbance elements, or each trio of additional disturbance elements, is sandwiched between two disturbance elements.

According to one of the aspects of the invention, the disturbance elements are arranged alternately on the first planar wall and on the second planar wall.

According to one of the aspects of the invention, the additional disturbance elements are arranged alternately on the first flat wall and on the second flat wall.

According to one of the aspects of the invention, two successive disturbance elements of the same wall are spaced apart by a pitch of between 3 and 10 mm, in particular between 4 and 7 mm, ideally 5.6 mm.

According to one of the aspects of the invention, a disturbance element and an additional disturbance element of the same wall are spaced apart by a pitch of between 3 and 10 mm, in particular between 4 and 7 mm, ideally 5.6 mm.

According to one of the aspects of the invention, a plane of symmetry S, passing through the top of the rafter, passes through the middle of the width L of the first flat wall.

According to one of the aspects of the invention, the pitch between either two disturbance elements, or a disturbance element and an additional disturbance element, increases progressively along the longitudinal direction of the tube.

According to one of the aspects of the invention, the disturbance elements are aligned along the longitudinal direction of the tube.

According to one of the aspects of the invention, the disturbance elements are made from material with the tube, in other words, the tube and the disturbance elements are made from the same block of material, one of which cannot be separated from each other without destroying the tube.

According to one of the aspects of the invention, the additional disturbance elements are made from material with the tube, in other words, the tube and the additional disturbance elements are made from the same block of material, one which can be separated from the other without destroying the tube.

According to one of the aspects of the invention, either the disturbance elements, or the disturbance elements and the additional disturbance elements, are manufactured by stamping, stamping or metal additive manufacturing.

According to one of the aspects of the invention, the tube comprises an intermediate wall dividing the internal duct defined inside the tube into two sub-channels.

According to one of the aspects of the invention, either the disturbance elements, or the disturbance elements and the additional disturbance elements, are arranged on one and the other of the sub-channels.

According to one of the aspects of the invention, the ratio of h2/e, h2 being the height of the additional disturbance elements, measured along a direction perpendicular to the first planar wall between the first internal face and the crest of the disturbance element additional, the first flat wall comprising a first external face facing the outside of the tube, e being the thickness of the first flat wall, measured in a direction perpendicular to the first flat wall between the first internal face and the first external face , this ratio is between 0.1 and 4.0, in particular between 0.5 and 2.5.

According to one of the aspects of the invention, the additional disturbance elements have a height h2 of between 0.2 mm and 0.5 mm, and in particular between 0.25 and 0.4 mm.

According to one of the aspects of the invention, the heat exchanger comprises a plurality of tubes, connected together through two manifolds, at least one of which is according to any one of the preceding claims, the tubes defining on the one hand internally a circulation circuit for a fluid capable of being disturbed in its passage by the presence of the disturbance elements and on the other hand defining between them a circulation space for air.

The features, variants and different embodiments of the invention may be associated with each other, in various combinations, insofar as they are not incompatible or exclusive of each other. It is possible in particular to imagine variants of the invention comprising only a selection of characteristics described in the present description in isolation from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage.

Other characteristics and advantages of the invention will become apparent through the description which follows on the one hand, and several embodiments given by way of indication and not limiting with reference to the appended diagrammatic drawings on the other hand, on which :

• There is a schematic representation, front view, of a heat exchanger consisting of a plurality of tubes according to the invention.
• There is a sectional view of a tube according to the invention, shown in perspective.
• There is a sectional view of the inside of the tube along a plane parallel to the wall of the tube.
• There is a top view, in section, of the interior of the tube, along a plane parallel to the wall of the tube, of a disturbance element according to the invention.
• There is a sectional view along the longitudinal direction of a tube according to the invention.
• There is a sectional view of the interior of the tube along a plane extending along the longitudinal direction and perpendicular to the wall of the tube, according to an embodiment of the invention comprising several geometries of disturbing elements.
• There is a graph showing the development of the improvement factor as a function of the Reynolds number measured for a reference tube and for a tube according to the present invention.

There shows a heat exchanger 1 according to the invention, configured to equip the front face of a vehicle, in particular for a motor vehicle, and to allow in particular an exchange of calories between two fluids, among which, by way of example, a fluid and airflow. The heat exchanger comprises a plurality of tubes 2 according to the invention, within which the fluid circulates. The tubes 2 are arranged parallel to each other in a stacking direction E, here vertical, and delimit a plurality of ducts in which the fluid can circulate.

The space between two successive tubes 2 according to the invention delimits a space 110 where a flow of air can circulate in order to exchange calories with the fluid circulating in the tubes 2. In order to increase the heat exchanges between the fluid and the air flow, fin-shaped dissipators 120 are arranged in the space where the air flow circulates. These dissipators 120 have the role of increasing the contact surface with the air flow to optimize the heat exchanges between fluid and air flow. In order to facilitate the reading of the and the vertical stacking of the tubes, the heatsinks 120 have only been shown partially, it being understood that they can extend over the entire longitudinal dimension of the tubes between which these heatsinks are arranged.

Each tube 2 according to the invention is connected to a first manifold 130 and to a second manifold 140 through which the fluid is caused to circulate and to supply the tubes. The first collector 130 is arranged to distribute the fluid entering the heat exchanger 1 in the various tubes 2 constituting said exchanger. The second collector 140 is arranged to collect the fluid having passed through the tubes 2 to make it leave the heat exchanger 1. The first and second collectors 130 and 140 are opposed to each other with respect to the stack of tubes 2, each tube extending longitudinally so as to be connected at a first end to the first manifold 130 and at a second end to the second manifold 140.

The heat exchanger 1 also comprises means for connecting these collectors with a fluid circuit external to the heat exchanger 1 and not shown here. The first manifold 130 is thus connected to a first connection end piece 150 through which the fluid can enter the heat exchanger 1, the second manifold 140 being connected to a second connection end piece 160 through which the fluid can leave the heat exchanger 1.

There shows the arrangement of the disturbance elements according to the invention. Tube 2 for heat exchanger 1 defines a fluid circulation channel 100, this channel having a longitudinal direction D. The length of this tube is defined along the longitudinal direction D.

This tube 2 comprises a first planar wall 3 extending in the longitudinal direction D. It comprises at least one disturbance element 10 present on this first planar wall 3, in the fluid circulation channel 100, so as to disturb the flow of this fluid. The disturbance element 10 includes in particular a local deformation of this first flat wall 3 of the tube towards the inside of the tube 2.

There also illustrates an embodiment in which the disturbance elements 10 are aligned along the longitudinal direction D of the tube 2.

There shows a tube sectional view along a plane parallel to the first planar wall 3 of the tube. There thus shows that the disturbance element 10 comprises a crest 20 having the shape of a chevron. The crest 20 comprises a first free end 14 and a second free end 15 between which the chevron extends.

The rafter is formed by two branches 12 and 13, each starting from one of the free ends, and these two branches join together at a peak 11. The peak 20 is contained in a plane parallel to the first flat wall 3. Otherwise said, the altitude of the crest 20 relative to the first flat wall 3 is substantially constant all along this crest 20.

The two branches 12 and 13 of the chevron are symmetrical to each other with respect to a plane of symmetry S, which plane S passes through the apex 11 and is defined both by the longitudinal direction D of the circulation channel 100 of fluid and by a direction perpendicular to the first planar wall 3.

The Illustrated Plan S passes both through the top 11 of the rafter and through the middle of the width L of the first flat wall 3.

There shows a cross-sectional top view, from inside the tube, of a disturbance element 10. The figure illustrates the width l of the disturbance element 10, measured between the first free end 14 and the second free end 15 of the crest 20 in the form of a chevron.

The first planar wall 3 comprises a first internal face 31 facing the fluid circulation channel 100, first planar wall 3 visible on the . This first internal face 31 has a width L measured in a direction perpendicular to the plane S. According to one aspect of the invention, the ratio l/L is between 0.6 and 1.0, in particular between 0.7 and 0, 9.

The branches 12, 13 forming the chevron form between them an angle 40 of between 100° and 140°, in particular between 110° and 130°, in particular 120°.

There shows a sectional view along the longitudinal direction D of a tube 2 according to the invention. The tube 2 comprises a first planar wall 3 and a second planar wall 4 extending in the longitudinal direction D. this second planar wall 4 is parallel to the first planar wall 3. This second planar wall 4 comprises a second internal face 41 facing to channel 100.

The figure illustrates a first height h of the disturbance elements 10, measured in a direction perpendicular to the first flat wall 3 between the first internal face 31 and the crest 20 of the disturbance element 10.

The height H of the channel 100 is measured in a direction perpendicular to the first flat wall 3 between the first internal face 31 and the second internal face 41.

The man/man ratio thus defined is between 0.1 and 0.4, in particular between 0.2 and 0.3.

The ratio of h/e, h being the height of the disturbance elements 10, the first flat wall comprising a first external face 32 facing the outside of the tube 2, e being the thickness of the first flat wall 4, measured according to a direction perpendicular to the first planar wall 3 between the first internal face 31 and the first external face 32, this ratio is between 0.1 and 4.0, in particular between 0.5 and 2.5.

According to one of the aspects of the invention, the height h of the disturbance elements 10 is between 0.1 and 0.6 mm, in particular between 0.2 and 0.5 mm.

The illustrated tube comprises an intermediate wall 50 dividing the internal duct defined inside the tube into two sub-channels 100, 101.

The tube comprises additional disturbance elements 30, in addition to the disturbance elements 10, and the crest of which has a shape different from the crest 20 of the disturbance elements 10, whether it is a chevron shape of dimension different, round, rectangular or oval for example, these shapes not being limiting.

The ratio of h2/e, h2 being the height of the additional disturbance elements 30, the first flat wall comprising a first external face 32 facing the outside of the tube 2, e being the thickness of the first flat wall 4, measured in a direction perpendicular to the first planar wall 3 between the first internal face 31 and the first external face 32, this ratio is between 0.1 and 4.0, in particular between 0.5 and 2.5.

The disturbance elements 10 and the additional disturbance elements 30 are arranged on one and the other of the sub-channels 100, 101.

The disturbance elements 10 and the additional disturbance elements 30 respectively have heights h and h2 of between 0.2 mm and 0.5 mm, and in particular between 0.25 and 0.4 mm.

There is a sectional view of the inside of the tube along a plane extending along the longitudinal direction D and perpendicular to the first planar wall 3 of the tube 2, according to an embodiment of the invention comprising several geometries of disturbing elements. In the case of the , the tube 2 comprises additional disturbance elements 30, in addition to the disturbance elements 10. The crest 20 of these additional disturbance elements 30 has a different shape from the disturbance elements 10. has additional disturbance elements 30, the crest 20 of which has the shape of small chevrons. The reduced size of the additional disturbance elements 30 makes it possible to insert two of them, along the width L of the tube. According to other embodiments, the crest 20 of these additional disturbance elements 30 can be round, rectangular or oval in shape.

According to an illustrated embodiment , the additional disturbance elements 30 are interposed between two disturbance elements 10. The disturbance elements 10 and the additional disturbance elements 30 are arranged alternately on the first flat wall 3 and on the second flat wall 4, being all arranged inside the channel 100 defined between these two walls.

In the example shown , a disturbance element 10 and an additional disturbance element 30 of the same wall are spaced apart by a pitch P of between 3 and 10 mm, in particular between 4 and 7 mm.

According to one of the aspects of the invention, the pitch P between either two disturbance elements 10, or a disturbance element 10 and an additional disturbance element 30, increases progressively along the longitudinal direction D of the tube 2. For the example shown , this pitch P is constant along the longitudinal direction D.

In the example shown , the disturbance elements 10 and the additional disturbance elements 30 are made in one piece with the tube 2. In other words, the tube 2, the disturbance elements 10 and the additional disturbance elements 30 are made from the same block of material, one of which cannot be separated from the others without destroying the tube 2. The disturbance elements 10 and the additional disturbance elements 30 can be manufactured by stamping, stamping or metal additive manufacturing.

There is a graph showing the evolution of the improvement factor, EHF, as a function of the Reynolds number, RE, measured for a reference tube D1 and for a tube according to the present invention D2. These data come from experimental measurements. The improvement factor is defined as the ratio of the Nusselt number of the tube considered by the Nusselt number of the reference tube D1 to equivalent Reynolds number, all divided by the ratio to the power 1/3 of the friction factor of the tube considered by the friction factor of the reference tube D1 at equivalent Reynolds number. The purpose of this coefficient is to compare the improvement in thermal performance by taking into account the impact on the pressure losses generated.

The reference tube used here is a tube developed specifically for high Reynolds numbers. The graph of the shows that the tube according to the invention has a greater improvement factor than the reference tube over the entire range tested, ie for Reynolds numbers ranging from 100 to 1000. This improvement varies according to the flow rates between 20% and 45%.

Claims (10)

Tube (2) for heat exchanger (1) defining a fluid circulation channel (100), comprising a first planar wall (3), comprising at least one disturbance element (10) present on this first planar wall (3) , in the fluid circulation channel (100), so as to disturb the flow of this fluid, the disturbance element (10) comprising in particular a local deformation of this first planar wall (3) of the tube (2) towards inside the tube (2), the disturbance element (10) comprising a crest (20) having the shape of a chevron, comprising two branches (12, 13) joining together at a vertex (11), the ratio of the width l of the disturbance element (10) over the width L of the first planar wall (3) is between 0.6 and 1.0, in particular between 0.7 and 0.9. Tube (2) according to the preceding claim, comprising a second flat wall (4), this second flat wall (4) being parallel to the first flat wall (3). Tube (2) according to the preceding claim, for which the ratio of the height h of the disturbance elements (10) to the height H of the channel (100) is between 0.1 and 0.4, in particular between 0.2 and 0.3. Tube (2) according to any one of the preceding claims, for which the ratio of the height h of the disturbance elements (10) to the thickness e of the first flat wall (4) is between 0.1 and 4, 0, especially between 0.5 and 2.5. Tube (2) according to any one of Claims 2 to 3, in which the disturbance elements (10) are arranged alternately on the first planar wall (3) and on the second planar wall (4), being all arranged at inside the channel (100) defined between these two walls (3, 4). Tube (2) according to any one of the preceding claims, in which the branches (12, 13) of the disturbance device (10) form between them an angle (40) of between 100° and 140°, in particular between 110° and 130°. Tubes (2) according to any one of the preceding claims, comprising additional disturbance elements (30), in addition to the disturbance elements (10), and whose crest (20) has a shape different from the crest (20) disturbance elements (10), whether it is a chevron shape of different size, rounds, rectangles or ovals. Tubes (2) according to the preceding claim, in which the number of additional disturbance elements (30) aligned along the width L of the first planar wall is greater than one. Tube (2) according to the preceding claim, in which a successive disturbance element (10) and an additional disturbance element (30) of the same wall are spaced apart by a pitch (P) of between 3 and 10 mm, in particular between 4 and 7 mm. Heat exchanger (1) comprising a plurality of tubes (2), interconnected through two collectors (130, 140), at least one of which is according to any one of the preceding claims, the tubes (2) defining on the one hand internally a circulation circuit for a fluid capable of being disturbed in its passage by the presence of the disturbance elements (10) and defining on the other hand between them a circulation space (110) for air.