EP3433560B1 - Heat exchanger and method for manufacturing same - Google Patents

Description

The invention relates to a heat exchanger and its manufacturing process. More particularly in the field of mechanical heat exchangers for an application in the automotive field. The invention relates more particularly to a heat exchanger and its manufacturing process according to the preambles of claims 1 and 8, respectively. Such an exchanger is known from the document EP 0 825 406 A2 .

• des tubes 3 parallèles les uns avec les autres et disposés en au moins un rang et dans lesquels un premier fluide caloporteur est apte à circuler, et
• des ailettes 4 évoluant parallèlement les unes par rapport aux autres et au travers desquelles un second fluide caloporteur 100 est apte à circuler, les ailettes 4 sont disposées perpendiculaires au plan du ou des rangs de tubes 3 et elles comportent des orifices 40 dans lesquels les tubes 3 sont insérés et fixés.

A mechanical heat exchanger 1, illustrated in figure 1 includes:

• tubes 3 parallel to each other and arranged in at least one row and in which a first heat transfer fluid is able to circulate, and
• fins 4 evolving parallel to each other and through which a second heat transfer fluid 100 is able to circulate, the fins 4 are arranged perpendicular to the plane of the row or rows of tubes 3 and they comprise orifices 40 in which the tubes 3 are inserted and fixed.

The attachment of the tubes 3 with the fins 4 is said to be mechanical, for example by widening said tubes 3. For this, an olive of size larger than that of the tubes 3 is inserted into the tubes 3 to enlarge said tubes 3, then removed. The tubes 3 are then widened and fixed to the fins 4.

However, this type of mechanical heat exchanger 1 and in particular the connection between the tubes 3 and the fins 4, has a high thermal resistance which penalizes the heat exchanges between the first and the second heat transfer fluid. Indeed, at the level of orifices 40, there is no continuous contact in particular when the fins 4 are hot and expanded. In fact, when the fins 4 expand, the size of the orifices 40 increases, which decreases the contact zones between the tubes 3 and the fins 4.

One of the aims of the present invention is therefore to at least partially remedy the drawbacks of the prior art and to propose an improved mechanical heat exchanger as well as its manufacturing process.

The present invention therefore relates to a heat exchanger according to claim 1.

According to one aspect of the invention, the angle that the fins form with the perpendicular to the axis of the tubes induces shear stresses between the tubes and the fins.

• les tubes parallèles les uns avec les autres et disposés en au moins un rang et dont les ailettes évoluent sans se croiser,
• lesdites ailettes comportant les orifices par lesquels passent les tubes de sorte à former au moins un groupe de tubes reliés entre eux par la superposition d'ailettes,

According to one aspect of the invention, the heat exchanger comprises:

• the parallel tubes with each other and arranged in at least one row and the fins of which evolve without crossing each other,
• said fins comprising the orifices through which the tubes pass so as to form at least one group of tubes connected to one another by the superposition of fins,

According to one aspect of the invention, the fins of the same group of tubes have a monotonic profile between two neighboring tubes.

According to one aspect of the invention, 20% of the tubes of the same group of tubes have the tangent to the surface of the fins at mid-distance between two neighboring tubes which forms an angle greater than or equal to 0.5 ° and less or equal to 10 ° with the perpendicular to the axis of the tubes.

The angle between the tangent to the surface of the fins midway between two neighboring tubes and the perpendicular to the axis of the tubes makes it possible to reduce the thermal resistance at the level of the orifices, in particular when the fins are dilated.

According to one aspect of the invention, the angle is greater than or equal to 0.5 ° and less than or equal to 5 °.

According to another aspect of the invention, the fins are flat.

According to another aspect of the invention, the fins are curved.

According to another aspect of the invention, the fins have a sinusoidal profile, the orifices and the tubes being placed at the level of ridges and hollows of said fins.

According to another aspect of the invention, the heat exchanger comprises a single group of tubes or at least two separate groups of tubes.

The present invention also relates to a manufacturing method according to claim 8.

According to one aspect of the method according to the invention, in the step of placing the tubes, the line connecting the ends of tubes of the same rank within the same group of tubes, has an angle greater than or equal to 0.5 ° and less than or equal to 10 ° with the perpendicular to the axis of the tubes.

According to one aspect of the method according to the invention, in the step of placing the tubes, the line connecting the ends of tubes of the same rank within the same group of tubes, has an angle greater than or equal to 0.5 ° and less than or equal to 5 ° with the perpendicular to the axis of the tubes.

According to one aspect of the method according to the invention, in the step of placing the tubes, the line connecting the ends of the tubes of the same group of tubes is a straight line.

According to another aspect of the method according to the invention, in the step of placing the tubes, the line connecting the ends of the tubes of the same group of tubes is a curve.

According to one aspect of the method according to the invention, in the step of placing the tubes, the line connecting the ends of the tubes of the same group of tubes is a sinusoid.

The present invention also relates to a manufacturing device for implementing the manufacturing method as described above, said device comprising alignment shoes intended to press on the ends of the tubes so that the ends of said tubes pass from 'a longitudinal position offset to an aligned position where the ends of said tubes are aligned with the perpendicular to the axis of the tubes.

• la figure 1 montre une représentation schématique en perspective d'un échangeur de chaleur mécanique selon l'art antérieur,
• la figure 2 montre une représentation schématique d'un échangeur de chaleur mécanique selon l'invention,
• les figures 3 à 6 montrent des représentations schématiques d'un échangeur de chaleur mécanique selon l'invention, selon différents modes de réalisations,
• la figure 7 montre une représentation schématique de la liaison entre les ailettes et les tubes,
• la figure 8 montre un diagramme de l'évolution de la résistance électrique en fonction de l'angle entre les ailettes et les tubes,
• la figure 9 montre un organigramme des différentes étapes du procédé de fabrication d'un échangeur de chaleur mécanique,
• les figures 10a à 10c montrent des représentations schématiques d'un échangeur de chaleur mécanique à différentes étapes de son procédé de fabrication,
• les figures 11 et 12 montrent des représentations schématiques d'un échangeur de chaleur mécanique à différentes étapes de son procédé de fabrication, selon différents modes de réalisations.

Other characteristics and advantages of the invention will appear more clearly on reading the following description, given by way of illustrative and nonlimiting example, and of the appended drawings among which:

• the figure 1 shows a schematic perspective representation of a mechanical heat exchanger according to the prior art,
• the figure 2 shows a schematic representation of a mechanical heat exchanger according to the invention,
• the figures 3 to 6 show schematic representations of a mechanical heat exchanger according to the invention, according to different embodiments,
• the figure 7 shows a schematic representation of the connection between the fins and the tubes,
• the figure 8 shows a diagram of the evolution of the electrical resistance as a function of the angle between the fins and the tubes,
• the figure 9 shows a flowchart of the different stages of the manufacturing process of a mechanical heat exchanger,
• the figures 10a to 10c show schematic representations of a mechanical heat exchanger at different stages of its manufacturing process,
• the Figures 11 and 12 show schematic representations of a mechanical heat exchanger at different stages of its manufacturing process, according to different embodiments.

Identical elements in the different figures have the same references.

The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the characteristics apply only to a single embodiment. Simple features of different embodiments can also be combined or interchanged to provide other embodiments.

In the present description, it is possible to index certain elements or parameters, such as for example first element or second element as well as first parameter and second parameter or even first criterion and second criterion etc. In this case, it is a simple indexing to differentiate and name elements or parameters or criteria that are close but not identical. This indexing does not imply a priority of an element, parameter or criterion over another and one can easily interchange such names without departing from the scope of this description. This indexing also does not imply an order in time for example to assess such or such criteria.

In the different figures, we will use an XYZ trihedron in order to show the angle of view of each of said figures in relation to each other. The axes of this trihedron can also correspond to the different orientations of the motor vehicle. The X axis can thus correspond to the axis of the length of the vehicle, the Y axis to the axis of its width and the Z axis to that of its height.

As the figure 1 corresponding to a prior art, a mechanical heat exchanger 1, comprises tubes 3 parallel to each other and arranged in at least one row and in which a first heat transfer fluid is able to circulate. For example, the refrigerant may come from a thermal management device such as air conditioning or from the cooling circuit of a thermal engine of a motor vehicle. These tubes 3 extend in particular in the plane defined by the axes Y and Z.

The heat exchanger 1 also comprises at least one superposition of fins 4, the fins 4 of which move parallel to one another, in particular parallel to the plane defined by the axes Y and Z. The fins 4 are therefore arranged perpendicular to the plane or rows of tubes 3. A second heat transfer fluid 100 is able to circulate between the fins 4, for example air. The fins 4 have orifices 40 through which tubes 3 pass so as to form at least one group of tubes 3 connected together by a superposition of fins 4.

• des tubes 3 parallèles les uns avec les autres et dans lesquels un premier fluide caloporteur est apte à circuler, et
• au moins une superposition d'ailettes 4 comportant des orifices 40 par lesquels passent des tubes 3.

As illustrated on figures 2 to 6 , the heat exchanger 1 comprises:

• tubes 3 parallel to each other and in which a first heat transfer fluid is able to circulate, and
• at least one superposition of fins 4 comprising orifices 40 through which tubes 3 pass.

The fins 4 form with a perpendicular to the axis of the tubes 3, that is to say with a parallel to the axis Y of the trihedron XYZ, an angle different from 0 °.

The tubes 3 are parallel with each other and arranged in at least one row and the fins 4 of which evolve without crossing. Said fins 4 comprise the orifices 40 through which the tubes 3 pass so as to form at least one group of tubes 3 connected together by the superposition of fins 4.

As illustrated on figures 2 to 6 showing the heat exchanger 1 and the figure 7 showing in more detail the connection between a fin 4 and two tubes 3, the fins 4 of the same group of tubes 3 have a monotonic profile between two neighboring tubes 3. In addition, at least 20% of the tubes 3 of the same group of tubes 3, have the tangent to the surface of the fins 4 midway between two neighboring tubes 3 which forms an angle α greater than or equal to 0.5 ° and less than or equal to 10 °, preferably less than or equal to 5 °, with the perpendicular to the axis of the tubes 3. This angle α between the tangent to the surface of the fins 4 midway between two neighboring tubes 3 and the perpendicular to the axis of the tubes 3 is particularly visible at the figure 7 .

The heat exchanger 1 can also include a water box 5 disposed at each end of the tubes 3. These water boxes 5 allow the collection and / or distribution of the first heat-transfer fluid so that it can pass through the tubes 3.

In a first embodiment illustrated in figure 2 , the fins 4 are flat and the heat exchanger 1 comprises a single group of tubes 3 grouping together all the tubes 3 of said heat exchanger 1. In this first embodiment, all of the tubes 3 are tangent to the surface fins 4 midway between two neighboring tubes 3 which forms an angle α greater than or equal to 0.5 °, and less than or equal to 10 ° with the perpendicular to the axis of the tubes 3.

The figure 3 shows a second embodiment where the fins 4 are curved. In this second embodiment, the heat exchanger 1 also comprises a single group of tubes 3 grouping together all the tubes 3 of said heat exchanger 1. In this second embodiment, all the tubes 3 do not have the tangent to the surface of the fins 4 midway between two neighboring tubes 3 which forms an angle α greater than or equal to 0.5 ° and less than or equal to 10 ° with the perpendicular to the axis of the tubes 3 due to the curved profile of the fins 4. Only at least 20% of the tubes 3 of the same group of tubes 3, have the tangent to the surface of the fins 4 midway between two neighboring tubes 3 which forms an angle α greater than or equal to 0.5 ° and less than or equal to 10 ° with the perpendicular to the axis of the tubes 3.

The figure 4 shows a heat exchanger 1 according to a third embodiment where the fins 4 have a sinusoidal profile. The orifices 40 of the fins 4 and the tubes 3 are here placed at the crests and hollows of the fins 4. In this third embodiment, the heat exchanger 1 also comprises a single group of tubes 3 grouping all the tubes 3 of said heat exchanger 1. Like the first embodiment, in this third embodiment, the set of tubes 3 has the tangent to the surface of the fins 4 midway between two neighboring tubes 3 which forms a angle α greater than or equal to 0.5 ° and less than or equal to 10 ° with the perpendicular to the axis of the tubes 3.

The Figures 5a and 5b show a heat exchanger 1 according to a fourth embodiment where the heat exchanger 1 comprises at least two groups of tubes 3. For the examples presented in Figures 5a and 5b , the heat exchanger 1 comprises four groups of tubes, each group of tubes 3 comprising two tubes 3. In each group of tubes 3, the tubes 3 are interconnected by a superposition of fins 4. In each group of tubes 3, the tubes 3 have the tangent to the surface of the fins 4 midway between two neighboring tubes 3 which forms an angle α greater than or equal to 0.5 ° and less than or equal to 10 ° with the perpendicular to the axis tubes 3. In the examples presented in Figures 5a and 5b , within each group of tubes 3, the fins 4 are flat. However, it is entirely possible to imagine that the fins 4, within each group of tubes 3, have a curved or even sinusoidal profile.

In the example of the figure 5a , the overlapping fins 4 of each group of tubes 3 have an identical orientation. In the example of the figure 5b , the overlaps of fins 4 of groups of tubes 3 successively have an inverted orientation, like an inverted reflection in a mirror.

It is also quite possible to imagine that, when the heat exchanger 1 comprises at least two groups of tubes 3, the angles α may differ from one group of tubes 3 to another, while remaining greater than or equal at 0.5 ° and less than or equal to 10 °.

As illustrated in figure 6 , the heat exchanger 1 may include covers 6 covering the space not occupied by the fins 4 between the fins 4 at the ends of the same group of tubes 3 and said water boxes 5. These covers 6 play a role barrier for the second heat transfer fluid 100 so that it cannot pass through this space not busy. The second heat transfer fluid 100 is then forced to circulate between the fins 4 which makes it possible not to deteriorate the heat exchanges.

The figure 8 shows a diagram of the evolution of the electrical resistance in mΩ, as a function of an angle α between 0 and 5 ° at the orifices 40 making the interface between the tubes 3 and the fins 4. The electrical resistance is easy to be measured and proportional to the thermal resistance. Thus the lower the electrical resistance, the lower the thermal resistance also.

The diagram of the figure 8 shows three curves 200, 201 and 202 corresponding to the variations of the electrical resistance for three samples of tubes 3 and fins 4 as a function of the angle a. The three curves 200, 201 and 203 show that the more the angle α increases, in particular beyond 0.5 °, the lower the electrical resistance and therefore the thermal resistance. By extrapolating curves 200, 201 and 203 and their average, an angle α of 10 ° appears as a saturation limit for the decrease in electrical resistance and therefore in thermal resistance. This means that from this value, an increase in the angle α would have little effect on the thermal resistance. As the figure 8 , an angle α between 0.5 and 5 ° is an optimal.

The effect of the angle α on the electrical resistance and therefore on the thermal resistance, is linked to the shear stresses between the fins 4 and the tubes 3 exerted by the angle a. These shear stresses allow good contact to be maintained between the tubes 3 and the fins 4 at the orifices 40, even if the fins 4 are expanded.

The present invention also relates to a method of manufacturing a heat exchanger 1 as described above. The figure 9 shows a flowchart of the different stages of said manufacturing process.

• une première étape 110, illustrée à la figure 10a, de mise en place de tubes 3 en au moins un groupe de tubes 3.

The manufacturing process includes the following steps:

• a first step 110, illustrated in figure 10a , placing tubes 3 into at least one group of tubes 3.

During this first step 110, the tubes 3 of the same group of tubes 3 are arranged parallel to each other with a longitudinal position offset. The imaginary line connecting the ends of the tubes 3 forms with a perpendicular to the axis of the tubes (3), that is to say with a parallel to the axis Y of the trihedron XYZ, an angle different from 0 °.

In particular, the line connecting the ends of the tubes 3 of the same rank within the same group of tubes 3, has an angle α 'greater than 0.5 ° and less than or equal to 10 °, preferably less than or equal to 5 °, with the perpendicular to the axis of the tubes 3.

• une deuxième étape 112, illustrée à la figure 10b, de fixation des tubes 3 aux ailettes 4.

During this first step 110, the tubes 3 have a diameter smaller than that of the orifices 40 of the fins 4 so that they can be inserted therein.

• a second step 112, illustrated in figure 10b , for fixing the tubes 3 to the fins 4.

• une troisième étape 114, illustrée à la figure 10c, d'alignement sous contrainte des extrémités des tubes 3 de sorte que les extrémités desdits tubes 3 soient alignés avec une perpendiculaire à l'axe des tubes 3, c'est-à-dire avec une parallèle à l'axe Y du trièdre XYZ.

This second step 112 can be carried out by expansion of the tubes 3, that is to say by an increase in their diameter which comes to fix them in the orifices 40. This expansion of the tubes 3, can for example be carried out by insertion into the tubes 3 of an olive with a diameter greater than that of the tubes 3.

• a third step 114, illustrated in figure 10c , alignment under stress of the ends of the tubes 3 so that the ends of said tubes 3 are aligned with a perpendicular to the axis of the tubes 3, that is to say with a parallel to the axis Y of the trihedron XYZ .

During this third step 114, the angle α 'between the line connecting the ends of the tubes 3 and the perpendicular to the axis of the tubes 3, owing to the fact that the fins 4 and the tubes 3 are fixed together, is transferred to the angle α between the tangent to the surface of the fins 4 midway between two neighboring tubes 3 and the perpendicular to the axis of the tubes 3. The connection between the tubes 3 and the fins 4 will then be under shear stress improving heat exchanges.

This third step 114 can for example be carried out by the fact that the manufacturing device for implementing the manufacturing process comprises alignment shoes. These alignment shoes are intended to press on the ends of the tubes 3 so that the ends of said tubes 3 pass from their offset longitudinal position, illustrated in the figure 10b , at an aligned position where the ends of said tubes 3 are aligned with the perpendicular to the axis of the tubes 3, as illustrated in the figure 10c .

The shape of the line connecting the ends of the tubes 3 of the same rank within the same group of tubes 3 produced in the first step 110 determines the profile of the fins 4 of the heat exchanger 1. Thus, if this line is a straight line as shown in the figure 10a , the fins 4 will be flat at the end of the manufacturing process.

If this line is a curve as shown in the figure 11 , the fins 4 will also be curved at the end of the manufacturing process.

If this line is a sinusoid as shown in the figure 12 , the fins 4 will have a sinusoidal profile at the end of the manufacturing process.

The manufacturing process may also include, following the third step 114 of alignment under stress, a fourth step 116 of placing water boxes 5 on the ends of the tubes 3 and of placing covers 6 covering the space not occupied by the fins 4 between the fins 4 at the ends of the same group of tubes 3 and said water boxes 5.

Thus, it can be seen that the heat exchanger 1 due to the angle α between the tangent to the surface of the fins 4 midway between two neighboring tubes 3 and the perpendicular to the axis of the tubes 3 and constraints shear exerted by this angle α between the tubes 3 and the fins 4, reduces the thermal resistance at the orifices 40 especially when the fins 4 are expanded.

Claims (12)

1. Mechanical heat exchanger (1) comprising:

   - tubes (3) parallel to each other and in which a first heat transfer fluid is capable of circulating; and

   - at least one superposition of fins (4) comprising orifices (40), through which the tubes (3) pass,

   the fins (4) forming, in relation to an axis perpendicular to the axis of the tubes (3), an angle different from 0°, the exchanger being characterized in that it comprises a water box (5) disposed at each end of the tubes (3) and in that it comprises covers (6) covering the space not occupied by the fins (4) between the end fins (4) of the same group of tubes (3) and said water boxes (5).
2. Heat exchanger (1) according to Claim 1, comprising:

   - the tubes parallel to each other and disposed in at least one row and for which the fins (4) extend without intersecting;

   - said fins (4) comprising the orifices (40), through which the tubes (3) pass so as to form at least one group of tubes (3) connected together by the superposition of fins (4).
3. Heat exchanger (1) according to Claim 2, characterized in that the fins (4) of the same group of tubes (3) have an unvaried profile between two neighboring tubes (3).
4. Heat exchanger (1) according to Claim 3, characterized in that at least 20% of the tubes (3) of the same group of tubes (3) have the tangent to the surface of the fins (4) midway between two neighboring tubes (3) that forms an angle (a) that is greater than or equal to 0.5° and is less than or equal to 10° in relation to the axis perpendicular to the axis of the tubes (3).
5. Heat exchanger (1) according to Claim 4, characterized in that the angle (a) is greater than or equal to 0.5° and is less than or equal to 5°.
6. Heat exchanger (1) according to any one of the preceding claims, characterized in that the fins (4) are flat.
7. Heat exchanger (1) according to any one of the preceding claims, characterized in that the fins (4) are curved.
8. Method for manufacturing a mechanical heat exchanger (1) comprising:

   ↘ tubes (3) parallel to each other and in which a first heat transfer fluid is capable of circulating; and

   ↘ at least one superposition of fins (4) comprising orifices (40), through which the tubes (3) pass,

   said method comprising the following steps:

   • installing tubes (3) in at least one group of tubes (3), said tubes (3) of the same group of tubes (3) being disposed parallel to each other with a longitudinal position offset, the ends of the tubes being connected by a line that forms, in relation to an axis perpendicular to the axis of the tubes (3), an angle different from 0°;

   • fastening the tubes (3) to the fins (4);

   • aligning the ends of the tubes (3) under stress so that the ends of said tubes (3) are aligned in relation to an axis perpendicular to the axis of the tubes (3), the method being characterized in that it further comprises, following the step of aligning under stress, a step of installing water boxes (5) on the ends of the tubes (3) and of installing covers (6) covering the space not occupied by the fins (4) between the fins (4) at the ends of the same group of tubes (3) and said water boxes (5) .
9. Manufacturing method according to Claim 8, characterized in that, in the step of installing the tubes (3), the line connecting the ends of the tubes (3) of the same row within the same group of tubes has an angle (α') that is greater than or equal to 0.5° and is less than or equal to 10° in relation to the axis perpendicular to the axis of the tubes (3).
10. Manufacturing method according to either one of Claims 8 and 9, characterized in that, during the step of installing the tubes (3), the line connecting the ends of the tubes (3) of the same row within the same group of tubes (3) has an angle (α') that is greater than 0.5° and is less than or equal to 5° in relation to the axis perpendicular to the axis of the tubes (3).
11. Manufacturing method according to any one of Claims 8 to 10, characterized in that, in the step of installing the tubes (3), the line connecting the ends of the tubes (3) of the same group of tubes (3) is a straight line.
12. Manufacturing method according to any one of Claims 8 to 10, characterized in that, in the step of installing the tubes (3), the line connecting the ends of the tubes (3) of the same group of tubes (3) is a curve.

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