EP2856056A1

EP2856056A1 - Spacer for a heat exchanger and associated heat exchanger

Info

Publication number: EP2856056A1
Application number: EP13724572.6A
Authority: EP
Inventors: Isabelle Citti; Christian Riondet; Badr ALOUANE
Original assignee: Valeo Systemes Thermiques SAS
Current assignee: Valeo Systemes Thermiques SAS
Priority date: 2012-05-25
Filing date: 2013-05-21
Publication date: 2015-04-08
Also published as: FR2991034B1; JP2015517646A; FR2991034A1; US20150096726A1; WO2013174785A1; CN104334995A

Abstract

The invention concerns a spacer for a heat exchanger, said spacer (7) comprising a predefined number of substantially parallel planar walls (13; 113) connected two-by-two by folds (15), the planar walls (13; 113) comprising a plurality of louvers (171; 172) substantially inclined relative to the general plane (P) defined by a planar wall (13; 113). According to the invention, a planar wall (13; 113) further comprises at least one strap (19; 119₁, 1192, 1193, 1194) having longitudinal sides (21) that extend parallel to the planar wall (13; 113) and lateral sides (23) linked to the planar wall (13; 113) by means of at least one connecting rail (24). The invention also concerns a heat exchanger comprising a heat exchange bundle comprising a stack of parallel tubes (5) for the circulation of the fluid, the tubes having a tube width (l1), and a plurality of such spacers (7) disposed respectively between two tubes (5).

Description

Intercalaire for heat exchanger and associated heat exchanger

The invention is in the field of ventilation, heating and / or air conditioning of an electric or hybrid motor vehicle.

The invention relates to an interlayer for heat exchanger cooperating with such a facility and an associated heat exchanger.

An electric or hybrid motor vehicle, whose propulsion is provided at least partially by an electric motor, is commonly equipped with a ventilation system, heating and / or air conditioning to change the aero thermal parameters of the air to the inside the passenger compartment of the vehicle by delivering a flow of conditioned air inside the passenger compartment.

Such a packaging system can be used for example in summer for a need for cooling of the passenger compartment, but also for example the winter for a need for heating the cabin.

Generally, the conditioning system comprises at least one heat exchanger able to work in condenser mode or in evaporator mode as required.

The heat exchanger generally comprises a bundle of tubes and spacers, for example corrugated, also called corrugated fins, disposed between the tubes of the bundle and secured to these tubes, usually by brazing, by their respective folds.

The tube bundle is usually swept by a gas stream such as a stream of air that exchanges heat with another fluid, usually a heat transfer fluid, which circulates in the tubes of the bundle.

The corrugated spacers are generally formed from a metal strip and comprise a set of flat walls, connected in pairs by folds to form alternating corrugations.

Interlayers are known in which each of the flat walls is provided with a plurality of inclined louvers made by cutting and forming the strip. The louvers that comprise the corrugated dividers have for principal function to improve the heat exchange by an active mixing of the air flow which sweeps the beam, forcing a flow of air through the shutters.

Furthermore, such a heat exchanger can be adapted to work in evaporator or condenser mode and is for example arranged at the front face of the vehicle for a heat exchange between the fluid and a flow of air outside the vehicle.

In particular, for heating purposes, a known solution is to use the conditioning system in heat pump mode.

In this case, the external heat exchanger works in evaporator mode.

The disadvantage of such a solution when it is used in winter conditions is the risk of icing of the external heat exchanger working in evaporator mode due to the condensation of the water vapor in the air and its cooling in contact with the walls. In particular, the inserts inside the heat exchanger can be made of ice.

This has the effect of significantly reducing the heat exchange in this heat exchanger, and therefore the power and efficiency of the packaging system.

It is known from the prior art, a solution that consists of using the heat exchanger in condenser mode. To do this, the conditioning system is commonly used in air conditioning mode. Thus, the heat exchanger in condenser mode is traversed by hot gases which allows defrosting.

However, this solution also does not allow to remove the water retention in the tabs, so that each time the loop is used in air / air heat pump mode, the phenomenon can recur more frequently and more quickly.

According to a known solution of the prior art, it has been proposed a spacer that can be wider than the tubes and whose upstream portion, that is to say the portion facing the airflow is devoid of louver. Conversely, the part of the interlayer downstream, that is to say opposite to the air inlet has louvers. This makes it possible to limit the exchange with the air on the upstream part of the interlayer because of the absence of louver and thus to control the icing.

The disadvantage of such a solution is to reduce the heat exchange by the lack of louvers over a large width of the interlayer resulting in a reduction in efficiency.

According to another known solution, the interlayer is also provided wider than the tube and has a set of small louvers and not a full louver over the entire height of the spacer on the upstream and downstream parts of the spacer.

A major disadvantage is that the water formed during the first defrosting can stagnate between two folds in the upstream part of the interlayer and increases the risk of ice accumulation upstream of the exchanger. The invention therefore aims to at least partially overcome these disadvantages of the prior art by providing a spacer to better control frost formation and facilitate the flow of condensate during defrosting.

To this end, the subject of the invention is an interlayer for a heat exchanger, said interlayer comprising a predefined number of substantially parallel flat walls connected in pairs by folds, the flat walls comprising a plurality of louvers substantially inclined with respect to the plane. general defined by a flat wall, characterized in that a flat wall further comprises at least one strap having longitudinal sides extending parallel to the flat wall and side sides connected to the flat wall by means of at least one link ramp.

With such a thong the water retention is reduced and the condensates flow better during defrosting.

Said interlayer may further comprise one or more of the following characteristics, taken separately or in combination:

a flat wall has a substantially rectangular general shape and the longitudinal sides of a strap extend in the direction of the height of the flat wall,

a strap extends over a distance of the order of at least 75% of the height of the plane wall;

a strap has a generally band-like shape defining a plane substantially parallel to the plane defined by the plane wall, at least one strap is arranged on one end of the plane wall intended to face the arrival of a gas flow in the heat exchanger,

a flat wall comprises at least two strips oriented in two opposite directions,

a flat wall comprises at least two strips arranged symmetrically on two opposite ends of the plane wall,

said louvers are arranged on a substantially central part of a plane wall,

said interlayer is formed from a metallic material and a strap is made by cutting and folding the metallic material,

the flat walls respectively comprise at least two groups of louvers having a respective orientation, the louvers of a group being substantially identical,

said interlayer has a substantially undulating general shape, the plane walls being connected two by two by folds so as to form alternating corrugations.

The invention also relates to a heat exchanger in which circulates a fluid for heat exchange with a gas flow, said exchanger comprising a heat exchange bundle having a substantially parallelepipedal general shape and comprising:

a stack of parallel tubes for the circulation of the fluid, the tubes having a tube width, and

a plurality of spacers arranged respectively between two tubes so as to be traversed by the gaseous flow, such that the spacers have an interlayer width greater than the tube width so as to exceed the tubes and respectively comprise a predefined number of flat walls connected two by two by folds, the flat walls comprising a plurality of louvers substantially inclined relative to the plane defined by the flat walls,

characterized in that a planar wall further comprises at least one strap having longitudinal sides extending parallel to the flat wall and lateral sides connected to the plane wall by means of at least one connecting ramp, and arranged on the upstream end of the flat wall facing the arrival of the gas flow.

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

FIG. 1 is a front view of a heat exchanger, in particular for a motor vehicle,

FIG. 2a is a perspective view of a part of an interlayer and of two adjacent tubes of the heat exchanger of FIG. 1 according to a first variant,

FIG. 2b is a partial side view of the spacer and of the two adjacent tubes of FIG. 2a,

FIG. 2c is a sectional view of the insert of FIGS. 2a and 2b;

FIG. 3 represents a graph illustrating test results on an interlayer with or without a strap, showing the water retention over time during a first phase A of immersion of an interlayer sample in water, and the evolution of the flow of water during a second phase B of removal of the sample from the water,

FIG. 4a is a partial side view of an interlayer and two adjacent tubes of the heat exchanger according to a second variant,

FIG. 4b is a sectional view of adjacent dividers of FIG. 4a,

FIG. 5a is a partial side view of an interlayer and two adjacent tubes of the heat exchanger according to a third variant, and

- Figure 5b is a sectional view of adjacent tabs of Figure 5a.

In these figures, the substantially identical elements bear the same references.

Shown schematically in Figure 1, a heat exchanger 1 including motor vehicle. In particular, such an exchanger may be intended for use in a hybrid and / or electric vehicle. This is for example an external heat exchanger of a conditioning system for heating or cooling the passenger compartment of the vehicle.

Such an external heat exchanger is able to allow a calorie exchange between a fluid, in particular a coolant, and a gas flow such as an outside air flow.

The heat transfer fluid is for example a refrigerant, such as tetrafluoroethane known under the name of RI 34a, carbon dioxide C0 ₂ , or tetrafluoropropene known as HFO-1234yf.

Generally, an external heat exchanger is installed on the front of the vehicle so as to benefit from a dynamic air flow, as an outside air flow, when the vehicle is in motion.

According to various modes of operation of the conditioning system, the external heat exchanger is able to function as a condenser or as an evaporator.

In particular the external heat exchanger can be used as a condenser in an air conditioning mode to cool the vehicle interior and evaporator in a heat pump mode to warm the cabin. In evaporator mode, the outdoor heat exchanger allows heat to be taken in the form of heat from the outside air flow. In condenser mode, the fluid transfers heat to the outside air stream passing through the external heat exchanger.

It is also possible to control the external heat exchanger in condenser mode in an air conditioning mode to allow defrosting of the external heat exchanger.

In fact, when the external heat exchanger has a temperature lower than that of the outside air, or even negative, the humidity of the outside air condenses and freezes on this external heat exchanger. This is particularly the case when the external heat exchanger is used as an evaporator when the conditioning system is controlled in heat pump mode. The heat exchanger 1 comprises a heat exchange bundle 3. The bundle 3 has a generally parallelepipedal overall shape with a length L, a height h, and a width in the direction perpendicular to FIG. 1.

The beam 3 comprises:

a stack of parallel tubes and spacers 7 arranged between two tubes 5, and

- Two manifolds 9, 11 of the fluid, namely an inlet box 9 and an outlet box 11. The tubes 5 respectively have at least one fluid circulation channel.

The tubes 5 are for example substantially longitudinal flat tubes whose length extends parallel to the length L of the beam 3 (see Figure 1).

In addition, the tubes 5 open respectively by their opposite longitudinal ends in the manifolds 9 and 11. This allows the introduction of the fluid into the beam 3 through the inlet box 9 and the evacuation of the fluid through the outlet box 11. These inlet manifolds 9 and outlet 11 are associated with a fluid circuit in which the exchanger 1 is mounted.

The tubes 5 have a tube width or first width 1 ₁ (see FIGS. 2a, 2b) parallel to the direction of the width of the bundle 3.

The tubes 5 and the spacers 7 are for example metallic. By way of example, it is possible to provide tubes 5 and spacers 7 made of an aluminum alloy.

In particular, the spacers 7 may be formed from a metal strip, for example aluminum alloy.

The tubes 5 and the spacers 7 can be brazed together.

The spacers 7 are interposed between the fluid circulation tubes 5 to improve the heat exchange between the gas flow F (see Figure 2b), such as the outside air flow, and the fluid. Indeed, these spacers 7 disrupt the flow of the gas flow F and increase the heat exchange surface between the fluid and the gas flow F.

The spacers 7 have a length extending parallel to the length L of the beam 3.

The spacers 7 additionally have a width of interlayer or second width 1 ₂ parallel to the width 1 ₁ of the tubes 5 and the width of the beam 3. This second width 1 ₂ is greater than the first width l ₁₅ so that the inserts 7 protrude from the tubes 5.

In addition, the spacers 7 have a height h 'which defines the distance between two adjacent tubes 5.

The spacers 7 have for example a generally undulating form. There is also talk of interleaves 7 folded accordion-shaped.

With reference to FIGS. 1 and 2a, an insert 7 comprises a predefined number of plane walls 13.

The flat walls 13 are substantially rectangular with a height h 'corresponding to the height h' of the spacer 7.

These flat walls 13 are substantially parallel and are connected two by two by folds 15.

In the case of an interlayer 7 corrugated as in the example illustrated, the folds 15 are substantially rounded and the flat walls 13 are connected in pairs by folds 15 so as to form alternating corrugations.

The spacers 7 can be attached to the tubes 5 by their respective folds, for example by soldering.

In addition, the flat walls 13 comprise a plurality of louvers 17 _1; 17 ₂ substantially inclined relative to the general plane P defined by the flat walls 13 (see Figures 2a and 2b).

These shutters 17 _1; 17 ₂ respectively have a generally blade-like general shape.

The shutters 17 _1; 17 ₂ can be made by cutting and folding the material metal of tab 7.

These shutters 17 _1; 17 ₂ are for example arranged on a substantially central portion of the flat wall 13. The louvers 17 _1; 17 ₂ can also be arranged in line with the tube 5.

Two groups of shutters can be provided: a first group of shutters

17i and a second group of louvers 17 ₂ . The louvers of the same group may be substantially identical.

Each group of louvers 17 _1; 17 ₂ may have a respective orientation. According to the illustrated example, the louvers 17i of the first group are for example oriented towards the upstream part of the flat wall 13 while the louvers 17 ₂ of the second group are oriented towards the downstream part of the flat wall 13.

According to the embodiment described, once the spacer 7 assembled in the heat exchanger 1, the upstream portion of the plane 13 is facing the arrival of the gas flow F, and the downstream portion of the flat wall 13 is therefore opposed to the arrival of the gas flow F.

In addition, these louvers 17 _1; 17 ₂ can extend over the entire height h 'of the plane wall 13.

The shutters 17 _1; 17 ₂ thus define openings at a given opening angle, through which passes the gas flow F, which increases the heat exchange surface.

Moreover, in addition to these louvers 17 _1; 17 ₂ , a flat wall 13 further comprises at least one strap 19.

Such a strap 19 is for example made by cutting and folding the metal material of the insert 7.

The strap 19 once formed is, for example, offset with respect to the plane P defined by the plane wall 13.

Such offset d, or "offset" in English, is best seen in Figure 2c. Indeed, there is a depression of material forming the strap 19 with respect to the general plane P defined by the plane wall 13. According to the illustrated example, this depression is perpendicular to the general plane P defined by the plane wall 13. This offset d may be at least of the order of 0.1 mm. By way of example, an offset d of the order of 0.4 to 0.5 mm can be provided.

This strap 19 is for example arranged on at least one end of the plane wall 13. According to the illustrated example, the plane wall 13 is substantially rectangular and the strap 19 is formed on a longitudinal end of the plane wall 13.

More specifically, the strap 19 is made on an upstream end of the plane wall 13 intended to face the arrival of the gas flow F during assembly of the heat exchanger 1.

This arrangement of the strap 19 at the inlet of the gas flow F in the heat exchanger 1 is particularly advantageous because in the event of icing, for example due to the use of the heat exchanger 1 in evaporator mode, the accumulation of frost occurs first upstream of the heat exchanger 1. And, as will be described later, the strap 19 reduces the formation of frost because the strap 19 is less conducive to water retention for example compared to a louver 17 _1; 17 ₂ . Thus, the strap 19 helps to capture moisture upstream.

Alternatively or additionally, it is possible for interlayer 7 to have at least one strap 19 on a downstream end, namely intended to be opposite to the arrival of the gas stream in heat exchanger 1.

Furthermore, the strap 19 has for example a generally bandlike shape. This band defines a plane substantially parallel to the general plane P defined by the plane wall 13. Thus, the flat wall 13 comprising such a strap 19 thus has a substantially rectangular recessed shape.

By way of example, the width of this strap 19 may be of the order of at least 0.5 mm. For example, a width of the order of 2 mm can be provided.

The strap 19 has longitudinal sides 21 parallel and opposite, and side sides 23 parallel and opposite, so that the strap 19 is substantially rectangular shape.

The longitudinal sides 21 extend parallel to the flat wall 13 in the direction of the height h 'of the flat wall 13. This strap 19 may extend longitudinally over a distance of at least 75% of the height h' of the flat wall 13, even over a distance corresponding to the entire height h 'of the plane wall 13.

At least one of the longitudinal sides 21 of the strap 19 is intended to extend substantially to the right of the gas flow F.

The lateral sides 23 are connected to the plane wall 13 by means of at least one connecting ramp 24.

This strap 19 is therefore substantially parallel to the flow of the gas flow F, such as the air flow; which reduces the pressure drop.

The presence of such a strap 19 makes it possible to better control the formation of frost, especially in winter conditions, when the heat exchanger 1 is driven in an evaporator in a heat pump mode. The reduction in the amount of ice increases the exchange surface between the gas flow and the refrigerant, which improves the performance of the heat exchanger 1. And, the thimble 19 being flat condensates s 'flow better during defrosting.

This is shown diagrammatically in FIG. 3 illustrating test results using an interlayer sample 7 provided with strips 19 and an interlayer sample without strips 19.

In the graph of FIG. 3, the first curve C1, identified by means of diamonds, corresponds to an interlayer 7 provided with strips 19 and the second C2, identified by means of triangles, corresponds to an interlayer devoid of strips 19. ; this insert has only louvers 17 _1; 17 ₂ .

This graph illustrates:

a first phase A of immersion of a sample of interlayer 7 in water, so as to schematically illustrate the retention of water in the insert 7, and

a second phase B for withdrawing the interlayer sample 7 from the water, so as to schematically illustrate the flow of the water retained over time.

For example, the first immersion phase A is according to the test carried out for a duration of the order of 120 seconds. And, the second phase B starts at 120s.

The graph 3 has the abscissa time in seconds (s) and the ordinate the weight of the water in the interlayer in grams (g).

During the first phase A, it is found that the retention of water is more important in the interlayer provided with louvers 17 _1; 17 ₂ , but devoid of straps 19. This is illustrated by the second curve C2 which increases more rapidly during this first phase A.

On the contrary, the first curve C1 grows more slowly than the second curve C2. The water retention is therefore less important in the tab 7 provided with strips 19 than in the interlayer without strips 19.

The frost therefore hangs less on a thong 19 than on a louver 17 _1; 17 ₂ .

In addition, the Applicant has found that frost catches all the less that the offset d of the strap 19 relative to the general plane P defined by the plane wall 13 is important.

Then, when the sample is removed from the water, the flow is more efficient in the insert 7 provided with strips 19 (see curve Cl) due to the lower water retention compared to the interlayer without thongs 19 (curve C2).

It is therefore clear that the strap 19 makes it possible to reduce the formation of frost upstream of the spacer 7, and to improve drainage of the condensates during the defrosting step by controlling the heat exchanger 1 in condenser mode. Indeed, the strap 19 is substantially parallel to the flow of the gas flow F through the heat exchanger 1 which facilitates the flow of condensate. Interlayers 7 having a strap 19 on the upstream ends of the flat walls 13 have previously been described.

As a variant, more than one strap may be provided on one end of a flat wall 113, as illustrated in FIGS. 4a and 4b.

For example, two strips 119i and 119 _{2 may be provided} on an upstream end of a plane wall 113.

The straps 119 ₁ and 119 ₂ are for example substantially identical in shape to the strap 19 previously described with reference to FIGS. 2a to 2c, with longitudinal sides 21 and lateral sides 23 connected to the plane wall 113 by means of at least a connecting ramp 24.

These two strips 119 ₁ and 119 ₂ may for example be made so opposite. This opposition of the two straps 119 ₁ and 119 ₂ is better visible in Figure 4b. To do this, it is possible to make one of the straps 119 ₁ by depression in a first direction schematized by the arrow Si in Figure 4b, and the other strap 119 ₂ by depression in a second direction S ₂ opposite to the first direction Si . Thus, depression of the two strips 119 ₁ and 119 ₂ can be done in the direction perpendicular to the general plane P defined by the flat wall 13 but in two directions Si and S ₂ opposed. The two strips 119i and 119 ₂ thus formed are oriented in two directions Si and S ₂ opposite.

The offset d or "offset" of the two strips 119i and 119 ₂ relative to the general plane P defined by the plane wall 113 may be substantially identical.

Finally, it can also be provided that a flat wall 113 comprises at least one strap 119i, 119 ₂ , 119 ₃ , 119 ₄ on the two opposite ends of the flat wall (see Figures 5a and 5b). This design facilitates the manufacturing process of the interlayer 7.

In particular, one can provide at least two strips 119i, 119 ₂ , 119 ₃ , 119 ₄ arranged symmetrically with respect to the width 1 ₂ interlayer.

As said previously, the flat wall 113 has for example a generally rectangular general shape, and the two strips 119i, 119 ₂ , 119 ₃ , 119 ₄ are for example carried by the two opposite longitudinal ends of the plane wall 113.

In particular, a flat wall 113 may have at least two strips 119i,

119 ₂ , 119 ₃ , H9 ₄ respectively arranged on the upstream end of the plane wall 113 intended to be oriented facing the arrival of the gas stream F in the assembled heat exchanger 1, and on the downstream end of the wall plane 113 to be opposed to this arrival of the gas flow F.

It can be provided that the strips 119i, 119 ₂ , 119 ₃ , 119 ₄ are opposed in pairs. More specifically, the two strips 119i and 119 ₂ on the upstream end of the plane wall 113 are respectively oriented in two directions Si and S ₂ opposite. Similarly, the two strips 119 ₄ and 119 ₃ on the downstream end are respectively oriented in the two directions Si and S ₂ opposite. Thus, for example, when the strips 119i, 119 ₂ , 119 ₃ , 119 ₄ are made symmetrically, the two strips 119 ₁ and 119 ₄ extreme of the plane wall 113 are respectively oriented in the first direction If while that the two intermediate strips 119 ₂ and 119 ₃ are respectively oriented in the second direction S ₂ .

Furthermore, according to this embodiment, the shutters 17 _\ and 17 ₂ are for example arranged on a substantially central portion of the flat wall 113 and the strips 119 _{l 5} 119 _2, 119 _3, 119 ₄ are arranged on both other of these shutters \ 1 _\ and 17 ₂ .

It is therefore understood that a spacer 7 for heat exchanger 1, in particular an external heat exchanger, capable of being set in ice, for example during the use of the heat exchanger 1 in evaporator mode in winter conditions, provided with at least one strap 19, 119 _{l 5} 119 _2, 119 _3, 119 _4, allows to better control the formation of ice and to improve the flow of condensate at the operating tilting of the heat exchanger 1 mode condenser.

Such a heat exchanger may comprise an upstream end of a flat wall 13 of spacer provided with at least one strap 19, 119 _{l 5} 119 ₂ which is located projecting out of the tube 5.

Such a heat exchanger may also comprise a downstream end of a flat wall 13 of interlayer provided with at least one strap 119 ₃ , 119 ₄ which is located in line with at least one tube 5.

Claims

1. spacer for heat exchanger, said spacer (7) comprising a predefined number of plane walls (13; 113) substantially parallel and connected two by two by folds (15), the plane walls (13; 113) comprising a plurality of shutters (17 _1, 17 ₂ ) substantially inclined with respect to the general plane (P) defined by a plane wall (13; 113), characterized in that a plane wall (13; 113) further comprises at least one strap ( 19; 119 ₁₅ 119 ₂ , 119 ₃ , 119 ₄ ) having longitudinal sides (21) extending parallel to the plane wall (13; 113) and lateral sides (23) connected to the plane wall (13; 113). by means of at least one connecting ramp (24).

2. The spacer according to claim 1, wherein a plane wall (13; 113) has a substantially rectangular general shape and the longitudinal sides (21) of a strap (19; 119i, 119 ₂ , 119 ₃ , 119 ₄ ) s extend in the direction of the height (h ') of the plane wall (13; 113).

3. Spacer according to claim 2, wherein a strap (19; 119 _l5 119 _2, 119 _3, 119 ₄₎ extends over a distance of the order of at least 75% of the height (h ') of the plane wall (13; 113).

4. A spacer according to any one of the preceding claims, wherein a strap (19; 119i, 119 ₂ , 119 ₃ , 119 ₄ ) has a substantially band-like general shape defining a plane substantially parallel to the plane (P) defined by the flat wall (13; 113).

5. The spacer according to any one of the preceding claims, wherein at least one strap (19; 119i, 119 ₂ , 119 ₃ , 119 ₄ ) is arranged on one end of the plane wall (13; 113) intended to be oriented. facing the arrival of a gas stream (F) in the heat exchanger (1).

6. Interlayer according to any one of the preceding claims, wherein a plane wall (113) comprises at least two strips (119i, 119 ₂ , 119 ₃ , 119 ₄ ) oriented in two opposite directions.

An interlayer according to any one of the preceding claims, wherein a planar wall (113) has at least two straps (19; 119i, 119 ₂ , 119 ₃ , 119 ₄ ) symmetrically arranged on two opposite ends of the wall plane (113).

8. Spacer according to one of the preceding claims, wherein said louvers (\ Ί _\ 17 ₂₎ are arranged on a substantially central portion of a flat wall (13; 113).

9. Spacer according to one of the preceding claims, formed from a metallic material and wherein a strap (19; 119 _{l 5} 119 _2, 119 _3, 119 ₄₎ is made by cutting and bending the metallic material.

The spacer according to any one of the preceding claims, wherein the planar walls (13; 113) respectively comprise at least two groups of louvers (\ Ί _\ , 17 ₂ ) having a respective orientation, the louvers of a group being substantially identical.

11. The spacer according to any one of the preceding claims, having a substantially undulating general shape, the plane walls (13; 113) being connected in pairs by folds (15) so as to form alternating corrugations.

12. Heat exchanger in which a fluid circulates for a heat exchange with a gas flow (F), said exchanger (1) comprising a heat exchange bundle

(3) having a generally parallelepipedal general shape and comprising:

a stack of parallel tubes (5) for the circulation of the fluid, the tubes having a tube width (l _× ), and

a plurality of spacers (7) arranged respectively between two tubes (5) so as to be traversed by the gaseous flow (F), such that the spacers (7) have a spacer width (1 ₂ ) greater than the tube width (l _x ) of way to exceed the tubes (5) and respectively comprise a predefined number of planar walls (13; 113) connected in pairs by folds (15), the planar walls (13; 113) comprising a plurality of louvers (\ Ί _\ , 17 ₂ ) substantially inclined with respect to the plane (P) defined by the planar walls (13; 113), characterized in that a plane wall (13; 113) further comprises at least one strap (19; 119i, 119). ₂ , 119 ₃ , H9 ₄ ): having longitudinal sides (21) extending parallel to the plane wall (13; 113) and lateral sides (23) connected to the plane wall (13; 113) by means of at least one connecting ramp (24), and arranged on the upstream end of the plane wall (13; 113) facing the arrival of the gas flow (F).