EP2068106A1 - Corrugated fin with louvers for a heat exchanger - Google Patents

Abstract

The separator has a band shaped flat walls (14) connected in pair by creases (16), where the separator is formed from metal strip. The creases are extended in parallel for forming corrugations. Louvers (24) are placed in a width of each wall. The louvers have small sides (30, 32), and large sides (26, 28) that extend in a direction of the width of the wall. A plane (P) of the wall and each louver form an evolutive inclination angle from a value (alpha) in a region of the small side (30) until another value (beta) in a region of the small side (32) for conferring a twist shape to the louver.

Description

The invention relates to heat exchangers, especially for motor vehicles.

It relates more particularly to a corrugated spacer for heat exchanger, formed from a metal strip and comprising a set of strip-shaped flat walls, connected in pairs by folds extending parallel to each other to form alternating corrugations. and in which each of the walls has a height defined between two successive folds and is provided with a plurality of louvers made by cutting and forming the strip, the louvers having two large cut sides extending in the direction of the height of the wall and two small sides that connect to the plane of the wall.

Such corrugated inserts, also called corrugated fins, are used in the manufacture of heat exchangers. They are then placed between the tubes of a bundle and secured to these tubes, usually by brazing, by their respective folds.

The direction of the folds of the spacers corresponds to the length of the spacers, that is to say to the depth of the beam.

In the particular application to heat exchangers for motor vehicles, the bundle of tubes is usually swept by air that comes to exchange the heat with another fluid, usually a coolant, which circulates in the tubes of the bundle.

The louvers contained in the corrugated dividers have the main function of improving the heat exchange by an active mixing of the air which sweeps the beam. The design of these louvers is particularly delicate because they must optimize the heat exchange, without increasing the pressure losses.

The classic design of the spacers is to force a flow of air through blocks of shutters. The louvers are inclined with the same angle and the same geometry and they are arranged in series in groups. In each group, the louvers are parallel. An inversion of the opening angle, or angle of inclination, of the louvers is performed at each change of group of louvers.

In this conventional design, the flow of air in the spacers follows a path in two dimensions. In the longitudinal dimension, there is an air flow through the interlayer in its length. In the vertical dimension, the air flow is forced by the opening angles of the louvers. The air then follows a path that ripples vertically due to the alternation of the angle according to groups of louvers.

As a result, the heat exchange is not optimized because the flow is mainly bi-directional, the zones of intense heat exchange are located essentially on the first louvers of the interlayer, and the pressure losses are significant.

Various solutions have been proposed in order to further optimize the thermal performance of louver spacers of the type mentioned in the introduction.

Thus, the patent US 5,311,935 describes a geometric range of the height of the spacers for which the ratio between the heat exchange and the pressure drops is indicated as being optimized. This louvered interlayer design increases the performance gain, but this translates into an increase in the pressure drop.

The patent US 5,669,438 discloses interleaves louvers that direct the flow of air to the tubes and thus improve the thermal performance of the exchange surface. However, as before, these solutions generate an increase in the pressure loss, and that significantly.

The documents EP 166 655 , WO 2004/102102 , US 6,170,566 , EP 1 711 769 and US 2006/0157233 relate to solutions to cause disturbances of the airflow by breaking the boundary layers that form on the louvers. However, these solutions also have the disadvantage of increasing the pressure drop due to the passage of air in the interlayer.

The document WO 2006/028253 concerns shutters bent at 90 ° in order to disturb very strongly the flow of air. However, the associated pressure drop is very high and the effectiveness of this solution is therefore very compromised.

The documents US 7,040,386 and JP 2006/5 162 175 relate to inserts designs that direct the flow of air to the tubes and thus reduce the thickness of the thermal boundary layer that is created on the surface of the tubes. As a result, thermal performance is increased. But this is achieved by greatly disrupting the flow of air and creating accelerations of the latter, which causes a significant increase in the pressure drop.

Thus, in summary, the known solutions, even if they allow in some cases to improve the heat exchange performance, generate in all cases a significant increase in the pressure drop.

It is therefore an object of the invention to overcome the disadvantages of the known solutions mentioned above.

The invention proposes for this purpose that each louver forms with the plane of the wall an evolutionary inclination angle varying monotonously from a first value α in the region of a first small side to a second value β in the region of a second small side, which allows to give the louver a generally twisted shape.

According to a first exemplary embodiment, the angle of inclination has its vertex along a long side of the shutter. According to an alternative, the angle of inclination varies along a generatrix passing through the contact points of the shutter at the first and second short sides with the wall and is contained in the plane P.

By the term "generally twisted shape" is meant here a twisted, non-planar shape that can evolve continuously or discontinuously and can be, for example, a helical or substantially helical shape. The angle of inclination (also called opening angle) can vary continuously from the first value α to the second value β so that the louver has a continuous face.

It is also conceivable that this angle of inclination varies in stages from the first value α to the second value β, so that the louver has a discontinuous face formed facets angularly offset two by two.

The wall may comprise at least two blocks of louvers, the louvers of the same block may be identical or belong to at least two different types.

In another aspect, the invention relates to a heat exchanger comprising a bundle of parallel tubes and a plurality of corrugated inserts, as defined above, arranged between the tubes of the bundle and secured to the tubes by their respective folds.

This new spacer structure generates a three-dimensional flow of air that can generate more turbulence in the boundary layers and faster over the range of Reynolds numbers. This structure directs the flow of air to the walls of the tubes to thereby improve heat transfer between the fluids, usually fresh air that scans the tubes beam and a heat transfer fluid that circulates in the tubes of the beam.

Air mixing is more active because of the turbulence and the direction of air towards the walls of the tubes, so that heat exchange is more efficient and more extensive over the length of the interlayer. This mixing performed near the different walls creates a disturbance and therefore a reduction of the effects of the thermal boundary layer which acts as a resistance.

The direction of the flow of air through the interlayer is forced by the louvers which are put in series. Since each louver has an evolutionary angle of inclination, a softer and progressive direction of air is obtained in the direction of inclination of the louvers, which makes it possible to considerably reduce the pressure drops.

Studies carried out on the interleaves of the invention show that, for the different arrangements of shutter blocks, the pressure loss is reduced by about 25% compared to conventional spacers, the thermal performance being moreover substantially identical to that of conventional dividers.

• la figure 1 est une vue partielle de côté d'un intercalaire ondulé selon l'invention solidarisé à deux tubes successifs d'un faisceau d'échange de chaleur ;
• les figures 2a et 2b sont des vues schématiques en perspective de deux modes de réalisation d'une persienne à angle d'inclinaison évolutif selon l'invention ;
• la figure 3 est une vue schématique en perspective d'une partie d'un intercalaire ondulé comprenant une multiplicité de persiennes selon les figures 2a et 2b dont les angles d'inclinaison respectifs varient de persienne en persienne ;
• les figures 4a, 4b, 4c et 4d sont des vues partielles en perspective d'intercalaires ondulés comprenant des blocs de persiennes selon l'invention disposés suivant des agencements différents ;
• la figure 5 est une vue schématique en perspective d'une persienne à facettes ;
• la figure 6 montre différentes configurations d'extrémités de persiennes ;
• la figure 7 est une vue schématique en perspective d'un bloc constitué de persiennes identiques selon l'invention ;
• la figure 8 est une vue schématique en perspective d'un bloc constitué de deux types de persiennes disposées en alternance ;
• la figure 9 est une vue schématique en perspective d'un autre bloc constitué de deux types de persiennes disposées en alternance, dans une autre forme de réalisation ;
• la figure 10 est une vue schématique en perspective d'un bloc constitué de deux types de persiennes disposées en alternance, dans une autre forme de réalisation ;
• la figure 11 est une vue schématique en perspective d'un bloc constitué de trois types de persiennes disposées de façon répétée ;
• la figure 12 est un diagramme représentant des champs de température obtenus pour une vitesse amont de 5 mètres par seconde (régime turbulent) avec la configuration d'intercalaires selon la figure 4b dans différents plans de coupe selon l'axe Z;
• la figure 13 est un graphique montrant l'évolution du rapport du flux thermique sur la différence de températures en fonction de la position le long d'un intercalaire pour différentes configurations selon l'invention (figure 4a à 4d) et pour un intercalaire à persiennes classiques ;
• la figure 14 est un diagramme représentant des lignes de courant obtenues pour une vitesse amont de 5 mètres par seconde (régime turbulent) avec la configuration de la figure 4b, dans différents plans de coupe selon l'axe Z ;
• les figures 15a et 15b représentent des blocs de persiennes, dans lesquels chaque persienne présente deux facettes s'étendant respectivement de part et d'autre du plan de la paroi en étant séparées par une bande étroite qui s'étend dans le plan de la paroi selon deux modes respectifs de réalisation ;
• la figure 16 est un schéma montrant l'évolution de la découpe des persiennes du bloc de persiennes des figures 15a et 15b ; et
• la figure 17 est une vue en perspective partielle d'un bloc de persiennes dans lequel chaque persienne présente plus de deux facettes décalées angulairement deux à deux.

In the description which follows, made only by way of example, reference is made to the appended drawings, in which:

• the figure 1 is a partial side view of a corrugated insert according to the invention secured to two successive tubes of a heat exchange bundle;
• the Figures 2a and 2b are schematic perspective views of two embodiments of a sloping louver evolutionary according to the invention;
• the figure 3 is a schematic perspective view of a portion of a corrugated spacer comprising a plurality of louvers according to the Figures 2a and 2b whose respective angles of inclination vary from shutter to shutter;
• the Figures 4a, 4b, 4c and 4d are partial perspective views of corrugated inserts comprising blocks of louvers according to the invention arranged in different arrangements;
• the figure 5 is a schematic perspective view of a faceted louver;
• the figure 6 shows different configurations of louver ends;
• the figure 7 is a schematic perspective view of a block consisting of identical louvers according to the invention;
• the figure 8 is a schematic perspective view of a block consisting of two types of louvers arranged alternately;
• the figure 9 is a schematic perspective view of another block consisting of two types of louvers arranged alternately, in another embodiment;
• the figure 10 is a schematic perspective view of a block consisting of two types of louvers arranged alternately, in another embodiment;
• the figure 11 is a schematic perspective view of a block consisting of three types of louvers arranged repeatedly;
• the figure 12 is a diagram representing temperature fields obtained for an upstream speed of 5 meters per second (turbulent regime) with the spacer configuration according to the figure 4b in different section planes along the Z axis;
• the figure 13 is a graph showing the evolution of the ratio of the thermal flux on the temperature difference as a function of the position along an interlayer for different configurations according to the invention ( figure 4a to 4d ) and for an interlayer with classic louvers;
• the figure 14 is a diagram representing current lines obtained for an upstream speed of 5 meters per second (turbulent regime) with the configuration of the figure 4b , in different sectional planes along the Z axis;
• the Figures 15a and 15b are blocks of shutters, in which each louver has two facets respectively extending on either side of the plane of the wall being separated by a narrow band which extends in the plane of the wall in two respective modes of production ;
• the figure 16 is a diagram showing the evolution of the cutting of the shutters of the shutter block Figures 15a and 15b ; and
• the figure 17 is a partial perspective view of a block of shutters in which each shutter has more than two facets angularly offset two by two.

We first refer to the figure 1 which represents a portion of a corrugated insert 10 according to the invention, disposed between two parallel tubes 12 belonging to a bundle of tubes of a heat exchanger. The tubes 12 are "flat tubes". The corrugated insert 10 is formed from a one-piece metal strip, generally made of aluminum alloy, and comprises a set of plane walls 14 connected in pairs by folds 16 extending parallel to each other and to a direction given (perpendicular to the plane of the drawing) to form alternating undulations.

The folds 16 are joined by brazing to large faces 18 of the tubes 12 to form a heat exchanger bundle. This beam is formed of a multiplicity of tubes 12 and a multiplicity of corrugated tabs each disposed between two successive tubes of the beam, in a manner known per se.

The insert 14 has a vertical axis A, which is parallel to the axial direction of the tubes 12. The insert 14 has a length which extends in a direction perpendicular to the drawing and which also corresponds to the depth of the beam.

In the example shown, the flat walls 14 are parallel to each other, and the fold 16 which connects two successive walls is a "square fold" which comprises a flat bottom 20 which extends perpendicularly to the successive walls 14 and which is connected to the latter by rounding 22.

The spacer has a width 1 (corresponding to the width of a flat wall 14 and two folds 16) which, in the example, corresponds substantially to the distance separating the flat faces 18 vis-à-vis two tubes successive beam. Each of the walls 14 is provided with a plurality of louvers 24 which have the feature of having an evolutionary inclination angle.

The louvers 24 can be attached by their large side 26, as seen better on the figure 2a , or, according to an alternative embodiment according to the figure 1 , the louvers 24 are attached by their small sides 30 and 32, as we see better on the figure 2b .

Each of the louvers 24 is made by cutting and forming the strip and has two long sides 26 and 28 which are cut into the thickness of the strip and extend in the direction of the width 1 of the wall, and two short sides 30 and 32 which are connected without cutting to the plane P of the wall 14 considered.

As we see on the Figures 2a and 2b each louver 24 forms, with the plane P, an inclination angle, also called an opening angle, which varies monotonously (that is to say, always increasing or decreasingly) from a first value α in the region of a first small side (here the small side 30) up to a second value β in the region of a second small side (here the small side 32). In the exemplary embodiment of the figure 2a , the angle of inclination has its top S along a long side of the shutter, here the long side 26. According to the embodiment of the figure 2b , the angle of inclination varies along a generatrix passing through the contact points of the shutter 24 at the first small side 30 and the second small side 32 with the wall 14 and contained in the plane P.

In the exemplary embodiment of Figures 2a and 2b , the angle of inclination varies continuously from the first value α to the second value β so that the louver has a continuous face having a generally twisted shape, and more particularly a generally helical shape.

The first value α and the second value β correspond to angles of inclination which extend respectively on either side of the plane P of the wall. As a result, the shutter 24 comprises a neutral inclination line LN which is coplanar with the plane P of the wall and which corresponds to a zero value of the angle of inclination. This line of neutral inclination is represented by a broken line on the figure 2 . It is generally parallel to the direction of the folds 16 of the strip.

As indicated above, each wall 14 of a spacer preferably comprises several blocks of louvers and the louvers of the same block may be identical to each other or different.

We now refer to the figure 3 which shows an example of a block of shutters in which the shutters are different. Thus, in the example, a block 34 has N louvers 24 _i , namely 24 ₁ to 24 _N. The index "i" designates the sequence number of the shutter in a block. From the first louver 24 ₁ to the last louver 24 _N , the first value of the inclination angle varies from α ₁ to α _N according to a chosen law, while the second value of the angle of inclination varies. from β ₁ to β _N according to a chosen law.

Thus, not only the angle of inclination varies for the same louver, but it also varies from one louver to another. The two evolutive angles of respective values α and β will thus create a helical shape of the block of shutters as seen on the figure 3 and also on the figure 1 .

• Première persienne (i=1) : $${\mathbf{<figure-callout\; id="1"\; label="\alpha "\; filenames="imgf0002.png"\; state="\{\{state\}\}">\alpha </figure-callout>}}_1=0\mathrm{<figure-callout\; id="1"\; label="et\; \beta "\; filenames="imgf0002.png"\; state="\{\{state\}\}">et</figure-callout>}{\mathbf{\beta }}_{}{\mathbf{}}_1={\mathbf{\beta }}_{\mathrm{MAX}}$$
  
• Persiennes suivantes (2≤i≤N) : $${\mathbf{\alpha }}_{\mathrm{i}}={\mathbf{\alpha }}_{\mathrm{i}-1}+{\mathbf{\alpha }}_{\mathrm{MAX}}/\left(\mathrm{N}-1\right)$$
  
  $${\mathbf{\beta }}_{\mathrm{i}}={\mathbf{\beta }}_{\mathrm{i}-1}+{\mathbf{\beta }}_{\mathrm{MAX}}/\left(\mathrm{N}-1\right)$$
  
• Dernière persienne (i=N) _: $${\mathbf{\alpha }}_{\mathrm{N}}={\mathbf{\alpha }}_{\mathrm{MAX}}\mathrm{et}{\mathbf{\beta }}_{\mathrm{N}}=0$$
  

In the example of the figure 3 the angles of inclination of the louvers of the same block meet the following conditions:

• First louver (i = 1): $${\mathbf{<figure-callout\; id="1"\; label="\alpha "\; filenames="imgf0002.png"\; state="\{\{state\}\}">\alpha </figure-callout>}}_1=0\mathrm{and}{\mathbf{<figure-callout\; id="1"\; label="\beta "\; filenames="imgf0002.png"\; state="\{\{state\}\}">\beta </figure-callout>}}_1={\mathbf{\beta }}_{\mathrm{MAX}}$$
  
• Next louvers (2≤i≤N): $${\mathbf{\alpha }}_{\mathrm{i}}={\mathbf{\alpha }}_{\mathrm{i}-1}+{\mathbf{\alpha }}_{\mathrm{MAX}}/\left(\mathrm{NOT}-1\right)$$
  
  $${\mathbf{\beta }}_{\mathrm{i}}={\mathbf{\beta }}_{\mathrm{i}-1}+{\mathbf{\beta }}_{\mathrm{MAX}}/\left(\mathrm{NOT}-1\right)$$
  
• Last shutter (i = N) _: $${\mathbf{\alpha }}_{\mathrm{NOT}}={\mathbf{\alpha }}_{\mathrm{MAX}}\mathrm{and}{\mathbf{\beta }}_{\mathrm{NOT}}=0$$
  

In the relationships above, i denotes the order number of a louver in a block of louvers, N the number of shutters of the shutter block, α _MAX the maximum value of the value α and β _MAX the maximum value of the value β.

As a result, the neutral inclination line LN ( figure 2 ) is shifted from one shutter to the other as seen on the figure 3 . For the first louver 24 ₁ , the neutral tilting line LN is in the region of the short side 30 and as one approaches the last louver 24 N, this line moves gradually to reach the region the second small side 32.

In the example of the figure 3 , the sum of the first value α and the second value β is constant for each louver of a group of louvers. In this particular case, this constant value is between 20 ° and 45 °.

We now refer to Figures 4a to 4d which respectively show four different configurations of a spacer each of whose walls comprises two blocks of louvers, considering here the two successive walls 14 connected by a fold 16. The four blocks are designated here by the references 34 ₁ , 34 ₂ for the wall 14 and 34 ₃ and 34 ₄ for the lower wall. It can be seen that the blocks 34 ₁ to 34 ₄ comprise respective "valleys" 36 ₁ to 36 ₄ which extend obliquely and each of which is formed by the different lines of neutral inclination LN of the louvers of the block.

In the configuration of the figure 4a , the valleys 36 ₁ and 36 ₂ converge on the side of the fold 16 located to the right of the figure and, likewise, the valleys 36 ₃ and 36 ₄ converge towards the same fold 16.

In the configuration of the figure 4b , the valleys 36 ₁ and 36 ₂ are parallel to each other, as are the valleys 36 ₃ and 36 ₄ .

In the configuration of the figure 4c , the valleys 36 ₁ and 36 ₂ converge as in the case of the figure 4a , while the valleys 36 ₃ and 36 ₄ converge but in the opposite direction.

Finally, in the configuration of the figure 4d , the valleys 36 ₁ and 36 ₂ are parallel to each other. The valleys 36 ₃ and 36 ₄ are also parallel to each other but not parallel to the valleys 36 ₁ and 36 ₂ .

In order to avoid overlaps between the shutters of blocks 34 ₁ and 34 ₂ , on the one hand, and the louvers of blocks 34 ₃ and 34 ₄ , on the other hand, and to be able to use higher inclination angles, the spacers preferably have a square shape, as shown in FIG. figure 1 . This means in other words that the two walls 14 are parallel to each other and connected by a fold which has a wall 20 perpendicular to the two walls 14.

This also makes it possible to avoid undesirable interactions between the air flows caused by the louvers of the upper blocks 34 ₁ and 34 ₂ and the lower blocks 34 ₃ and 34 ₄ and thus to have an air flow directed solely by shutters.

However, the invention is not limited to interleaves having walls parallel to each other forming square folds and it can also be applied to interleaves having different shapes, for example sinusoidal shapes or the like. Thus, the walls of the strip can be parallel and connected two by two by sinusoidal folds.

According to an alternative embodiment, the walls of the strip are not parallel to each other. That is to say that two successive walls form a "sinusoidal fold" which has no flat bottom.

As mentioned before, in the example of figure 3 , and in that of Figures 4A to 4D , the sum of angles α and β is between 20 ° and 45 ° for each louver.

Preferably, the width of each louver (as defined between the two long sides 26 and 28) will generally be between 0.8 and 1.4mm. Generally, it is preferred that this width is constant, but it is also possible to vary the width of the louvers along a spacer.

In the examples of the preceding figures, each louver has a continuous surface between its two ends, that is to say between its two short sides 30 and 32.

However, the interlayer can be provided with louvers with several facets as shown on the figure 5 . In this example, the shutter has two facets 38 and 40 both in the shape of a right triangle which are connected along a connecting edge 42 which extends in diagonally or obliquely. In this particular case, the shutter does not have a zero inclination angle between the first value α and the second value β. The evolution of the first value α to the second value β is above and below the plane P.

For each end of louvers, different configurations are possible, as shown in figure 6 which has seven distinct configurations, numbered 1, 2, 3, 4, 5, 6 and 7 from left to right. In configuration 1, the angle of inclination is above the plane and has its vertex oriented to the left. In configuration 2, the tilt angle is below the plane and has its vertex oriented to the left. In configuration 3, the angle of inclination is above the plane and has its vertex oriented to the right. In configuration 4, the tilt angle is below the plane and has its vertex oriented to the right. In the configuration 5, the angle of inclination is zero. In the configuration 6, the angle of inclination is on both sides of the plane in a first direction of inclination. Finally, in the configuration 7, the angle of inclination is on both sides of the plane in a second direction of inclination opposite the inclination of the configuration 6.

Thus, either the two ends have different configurations, or the two ends have identical configurations but with different angles (α and β).

We now refer to the figure 7 which shows a block of shutters with all louvers identical and designated by reference 24 ₁ . In the example, the angle of inclination of each louver varies from a first value α ₁ to a second value β ₁ , and this continuously, the fin having a generally helical shape.

However, louvers in the same block can belong to different types.

So, in the case of the figure 8 , the shutters of the same block belong to two different types (louvers 24 ₁ and 24 ₂ ) and are arranged alternately. The angle of inclination of a shutter 24 ₁ varies from a value α ₁ to a value β ₁ and the angle of inclination of a louver 24 ₂ varies from a value α ₂ to a value β ₂ . In the example of the figure 8 , the angles α ₁ , α ₂ , β ₁ and β ₂ are never zero.

In the example of the figure 9 , louvers of the same block belong, there too, to two different types (louvers 24 ₁ and 24 ₂ ) and are arranged alternately. The angles β ₁ and α ₂ are zero, while the angles α ₁ and β ₂ are equal and not zero. In addition, the louvers are open face to face, the inclination angles being opposite two by two.

In the example of the figure 10 , the block consists of two different types of louvers (louvers 24 ₁ and 24 ₂ ) arranged alternately. The angles α ₁ and β ₂ are zero, while the angles β ₁ and α ₂ are equal and not zero.

In the example of the figure 11 , the louvers of the same block belong to three different types (louvers 24 ₁ , 24 ₂ and 24 ₃ ). Their respective inclination angles range from a first value α ₁ , α ₂ , α ₃ to a second value β ₁ , β ₂ and β ₃ . These louvers are arranged repeatedly, in groups of three louvers 24 ₁ , 24 ₂ and 24 ₃ always in the same order.

The invention is not limited to the configurations of louvers or louver blocks described above, which have been given only by way of example. A multiplicity of louvre arrangements are possible, each arrangement being chosen preferentially according to the desired performance and pressure drop.

The louvers of the invention can be obtained by appropriate tools, such as for example rotating discs, ensuring the cutting and forming of louvers. The configuration and arrangement of the louvers has, each time, an influence on the number of different disks to achieve and their complexity.

It is possible, for example, to use a set of disks different from each other, in which each disk has identical teeth.

Alternatively, it is possible to use identical discs but having different teeth, each disc being angularly offset from the previous disc and / or relative to the next disc.

The following table compares the results obtained in terms of thermal performance and pressure drop for the spacers of the Figures 4a to 4d and for a classic interlayer taken as a reference.

The table shows the values obtained each time for the power exchanged (expressed in Watt) and the pressure drop ΔP (expressed in Pascal) for a laminar flow of an air flow with an upstream speed of 2 meters per second. and for a turbulent flow of air flow with an upstream speed of 5 meters per second. The four interlayer configurations of the invention make it possible to reduce the pressure drop by approximately 25% compared to the conventional interlayer, the heat exchange power being approximately the same as that of the conventional interlayer. In addition, the configuration of the tab of the figure 4b also allows a slight gain in thermal performance, which shows the interest of having the same orientation of louvers on all blocks. <U> Table </ u> intercalary classical Fig. 4a Fig. 4b Fig. 4c Fig. 4d U _upstream = 2m / s Laminate P _exchanged (W) 100 97 102 102 102 .DELTA.P (Pa) 100 76 77 75 76 U _upstream = 5m / s Turbulent P _exchanged (W) 100 95 100 99 99 .DELTA.P (Pa) 100 72 73 72 76

We now refer to the figure 12 which shows the temperature fields obtained for a speed of 5 meters / second of the airflow (turbulent regime) on the configuration of the figure 4b in different section planes along the Z axis which corresponds to the axis of the width of the interlayer. It will be understood that the heat exchange is highly dependent on the position along the Z axis, contrary to what is known for a conventional interlayer.

The figure 13 shows the evolution of the ratio of the heat flux on the temperature difference, in W / K, as a function of the position along the interlayer for the spacers of the Figures 4a to 4d and for an interlayer with classic louvers. Curve C ₁ corresponds to the spacers of Figures 4a and 4b , while the curve C ₂ corresponds to the spacers of the Figures 4c and 4d and that the curve C ₃ corresponds to the conventional interlayer. The curves show that the most intense heat exchanges take place on the first part of the interlayer (low values of the length of interlayer) and that the exchanges are higher than for the classic interlayer on the last three quarters of the interlayer (high values of the interlayer length). The high heat exchange zones are therefore better distributed on the inserts of the invention than on the conventional interlayer.

The figure 14 shows the current lines obtained for a speed of 5 meters per second (turbulent regime) on the configuration of the Figure 4B , in different section planes along the Z axis. This figure makes it possible to understand where the reduction in pressure drops tab. Indeed, the entire flow is not disturbed in the same place and overall this flow is significantly less disturbed along its length than on a conventional spacer.

Reference is now made to FIGS. 15a, 15b and 16 which show a block of louvers in which the angle of inclination varies in stages. Here, the shutter has two facets 44 _i and 46 _i extending respectively on either side of the plane P of the wall and separated by a narrow strip 48 extending in the plane P. The set of narrow strips 48 In an alternative embodiment (not shown), this narrow band may be omitted.

The Figures 15a and 15b different from each other by the embodiment of the louvers. Thus, the shutters of the block of the figure 15a are made identically to the shutters of the figure 2a . Conversely, the blinds of the block of the figure 15b are made identically to the shutters of the figure 2b .

Moreover, the embodiment of the figure 15b does not have a narrow band separating two successive louvers.

Referring to the figure 16 the first louver has a single facet 44 ₁ extending from one side of the plane P. The second louver has a facet 44 ₂ on one side of the plane and a facet 46 ₂ on the other side of the plane and so to the last louver which includes a single 46 _N facet that extends on the other side of the plane. These facets each have a flat surface. The block of louvers can thus be obtained by positive and negative cuts with a stepwise shift of the relative length of the positive cutting part (facet 44 _i ) and the negative cutting part (facet 46 _i ) of a shutter to the other.

We now refer to the figure 17 which shows another variant in which the louvers have a generally helical shape similar to that shown on the figure 2 . However, each of the louvers 24 _i has a discontinuous face consisting of a plurality of facets 50, here five in number for each louver. These facets are flat and are angularly offset from adjacent facets to form bearings or steps.

The corrugated louvers according to the invention find particular application in heating, ventilation and / or air conditioning of motor vehicles, in particular in the production of heat exchangers for motor vehicles incorporated in these installations. These may include engine cooling radiators, cabin heater radiators, condensers, gas coolers or air conditioning system evaporators, charge air coolers, etc.

The tubes of the heat exchangers can be of any known type. They include bent tubes, welded, extruded, etc ... but also tubes made by assembling plates or the like.

Of course, the invention is not limited to the embodiments described above and provided only to As an example and includes other variants that may be considered by those skilled in the art within the scope of the claims and in particular any combination of the various embodiments described above.

Claims (23)

Corrugated spacer for heat exchanger, formed from a metal strip and comprising a set of strip-shaped flat walls (14) connected in pairs by folds (16) extending parallel to each other to form corrugations alternating, and wherein each of the walls (14) has a width (1) defined between two successive folds and is provided with a plurality of louvers (24) made by cutting and forming the strip, the louvers having two long sides (26). , 28) cut in the direction of the width (1) of the wall and two short sides (30, 32)
characterized in that each louver (24) forms with the plane (P) of the wall (14) an evolutionary inclination angle from a first value (α) in the region of a first small side (30) to a second value (α) in the region of a second small side (32), which gives the louver a generally twisted shape. Corrugated spacer for heat exchanger according to claim 1, characterized in that the angle of inclination varies continuously from the first value (α) to the second value (α), so that the louver has a continuous face. Corrugated spacer for heat exchanger according to claim 1, characterized in that the first value (α) and the second value (α) correspond to angles of inclination which extend respectively on either side of the plane (P). ) of the wall (14). Corrugated spacer for heat exchanger according to one of claims 2 and 3, characterized in that , from a first louver (24 ₁ ) to a last louver (24 _N ), the first value varies respectively from α ₁ to α _N according to a chosen law, while the second value varies respectively from α ₁ to α _N according to a chosen law. Corrugated spacer for heat exchanger according to one of claims 2 to 4, characterized in that the angles of inclination of the louvers meet the following conditions. First louver (1 = 1): α ₁ = 0 and α ₁ = α _MAX Next louvers (2≤i≤N): α _i = α _i-1 + α _MAX / (N-1) and α _i - α _i-1 - α _MAX / (N-1) Last shutter (i = N): α _N α _MAX and α _N = 0 where i denotes the order number of a shutter in a block of shutters, N the number of louvers of the shutter block, to the maximum value of the value α and α _MAX the maximum value of the value α. Corrugated spacer for heat exchanger according to one of claims 1 to 5, characterized in that each louver (24) comprises a neutral inclination line (LN) which is coplanar with the plane (P) of the wall (14) and corresponds to a zero value of the angle of inclination. Corrugated spacer for heat exchanger according to claim 6, characterized in that the neutral inclination line (LN) is shifted from one shutter to the other. Corrugated spacer for heat exchanger according to one of claims 2 to 7, characterized in that the sum (α + α) of the first value (α) and the second value (α) takes a constant value for each shutter of 'a group of shutters. Corrugated spacer for heat exchanger according to Claim 8, characterized in that the constant value is between 20 ° and 45 °. Corrugated spacer for heat exchanger according to claim 1, characterized in that the angle of inclination varies in steps from the first value (α) to the second value (α), so that the louver has a discontinuous face formed of facets (50) angularly offset two by two. Corrugated spacer for heat exchanger according to claim 10, characterized in that the louver has more than two facets (50). Corrugated spacer for heat exchanger according to claim 11, characterized in that the facets (50) are angularly offset in pairs. Corrugated spacer for heat exchanger according to claim 10, characterized in that the louver has two facets (44, 46) respectively extending on either side of the plane (P) of the wall. Corrugated spacer for heat exchanger according to Claim 13, characterized in that the two facets (44, 46) are separated by a narrow band (48) extending in said plane (P) of the wall. Corrugated spacer for heat exchanger according to one of claims 1 to 14, characterized in that the wall (14) comprises at least two blocks (34) of louvers (24). Corrugated spacer for heat exchanger according to claim 15, characterized in that the louvers (24) of a block of louvers are identical. Corrugated spacer for a heat exchanger according to claim 15, characterized in that the louvers of a block of shutters belong to two different types (24 ₁ , 24 ₂ ) and are arranged alternately, the angle of inclination of a louver (24 ₁ ) of a first type varying from a value α ₁ to a value α ₁ and the angle of inclination of a louver (24 ₂ ) of a second type varying from a value α ₂ to a value α ₂ . Corrugated spacer for heat exchanger according to claim 17, characterized in that the angles α ₁ and α ₂ are zero, while the angles α ₁ and α ₂ are equal and not zero. Corrugated spacer for heat exchanger according to claim 17, characterized in that the angles α ₁ and α ₂ are zero, while the angles α ₁ and α ₂ are equal and not zero. Corrugated spacer for heat exchanger according to claim 15, characterized in that the louvers of a block of shutters belong to three different types (24 ₁ , 24 ₂ , 24 ₃ ) and are arranged repeatedly. Corrugated spacer for heat exchanger according to one of claims 1 to 20, characterized in that the walls (14) of the strip are parallel and connected in pairs by square folds (16). Corrugated spacer for heat exchanger according to one of claims 1 to 20, characterized in that the walls (14) of the strip are connected in pairs by sinusoidal folds (16). Heat exchanger comprising a bundle of tubes (12) parallel and a plurality of corrugated inserts (10) according to one of claims 1 to 22 disposed between the tubes of the bundle and attached to the tubes by their respective folds (16).

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