EP2877802A1

EP2877802A1 - Multi-fluid heat exchanger for motor vehicles

Info

Publication number: EP2877802A1
Application number: EP13744477.4A
Authority: EP
Inventors: Alain Bauerheim
Original assignee: Valeo Systemes Thermiques SAS
Current assignee: Valeo Systemes Thermiques SAS
Priority date: 2012-07-24
Filing date: 2013-07-24
Publication date: 2015-06-03
Also published as: FR2993965A1; FR2993965B1; WO2014016324A1

Abstract

The invention relates to a multi-fluid heat exchanger (1) for a vehicle including: a first high-pressure fluid circuit (3) including at least a first flat tube (7) enabling the circulation of a first fluid (11) at a first pressure, said first flat tube (7) including a first inner insert (49), the ridges (51) of which are attached to an inner wall of the first flat tube (7); a second liquid fluid circuit (5) including a second flat tube (9) enabling the circulation of a second liquid fluid (13) at a second pressure lower than the first pressure, characterized in that said first flat tube (7) and said second flat tube (9) are bent tubes having a similar outer shape, and in that the number of ridges (51) of the first inner insert (49) is sized such as to enable the first flat tube (7) to resist the pressure of the first fluid (11).

Description

Multi-fluid heat exchanger for motor vehicles

The present invention relates to a multi-fluid heat exchanger, in particular for motor vehicles.

A multitude of fluids circulates in a motor vehicle. This multitude of fluid comprises for example a refrigerant used for the air conditioning system of the vehicle, a lubricating oil of the engine, or even water used to cool the vehicle electronics.

The temperature of each of these fluids must be monitored and controlled to ensure optimal vehicle operation. For this purpose heat exchangers are implemented, for example condensers which are used to control the temperature of the cooling liquid or for example oil coolers.

To cool the electronics of hybrid or electric vehicles, it is generally used a low temperature water circuit which itself is cooled by a low temperature radiator. Since the heat exchange requirement is low, for example less than 1 kW, a small surface radiator is generally added upstream of all the heat exchangers in the front part of the vehicle.

To reduce the bulk in the front of the vehicle, there are multi-fluid heat exchangers comprising a plurality of heat exchangers.

For example, a multi-fluid heat exchanger is known comprising a first heat exchanger for cooling a first fluid, and a second heat exchanger for cooling a second fluid.

In addition to reducing the size, these multi-fluid heat exchangers have the advantage of simplifying the assembly of the heat exchangers in the motor vehicle as well as reducing the costs of manufacturing and production, in fact reducing the number of elements.

A multi-fluid heat exchanger comprises a plurality of elements, generally a pair of manifolds connected by a bundle of tubes substantially parallel to each other. This bundle of tubes allows the circulation of fluids from one collector box to another.

However, the different fluids do not have the same physical properties and exert different constraints on the multi-fluid heat exchanger tubes. In order to optimize the heat exchange for the different fluids, a known solution is to adapt the shape of the tubes according to the nature of the fluids. For example, the adaptation of the diameter or shape of the tubes is known. However, this requires manufacturing as many tube models as fluids. Consequently, the shape of the manifolds must be adapted according to the tube models and therefore fluids. By increasing the number of models of the elements of the multi-fluid heat exchanger, the manufacture is complicated and the production costs are increased.

The invention therefore aims to at least partially overcome the disadvantages of the prior art by providing a multi-fluid heat exchanger that can easily be optimized fluids through it.

For this purpose, the subject of the invention is a multi-fluid heat exchanger for a motor vehicle comprising:

A first high pressure fluid circuit comprising at least a first flat tube allowing the circulation of a first fluid at a first pressure, said first flat tube comprising at least a first corrugated inner spacer whose ridges are fixed with a wall internal of the first flat tube,

A second liquid fluid circuit comprising at least a second flat tube allowing the circulation of a second liquid fluid at a second pressure lower than the first pressure,

characterized in that said first flat tube and said second flat tube are folded tubes having a similar outer shape, and in that the number of ridges of the first inner spacer is sized to allow the first flat tube to withstand the pressure of the first fluid.

According to another aspect of the multi-fluid heat exchanger, the first fluid circuit is in the form of a condenser, and the second liquid fluid circuit is in the form of a radiator.

According to another aspect of the multi-fluid heat exchanger, at least one second tube of the second liquid fluid circuit comprises a second inner spacer.

According to another aspect of the multi-fluid heat exchanger, at least one second end tube of the second liquid fluid circuit comprises a second inner spacer. According to another aspect of the multi-fluid heat exchanger, wherein the first fluid circuit and the second liquid fluid circuit have different temperatures, the second inner end tube comprises a second inner spacer.

According to another aspect of the multi-fluid heat exchanger, the peaks of the second internal spacers are fixed with the inner wall of the second flat tubes.

According to another aspect of the multi-fluid heat exchanger, the first flat tubes and second flat tubes being connected to a first common header and a second common header, the first manifold and the second manifold each comprise a double inner wall for separating the first fluid circuit and the second liquid fluid circuit.

According to another aspect of the multi-fluid heat exchanger, the first pressure reaches up to 35 bars absolute, and the second pressure is substantially atmospheric.

According to another aspect of the multi-fluid heat exchanger, the first flat tubes and the second flat tubes are tubes substantially bent "B" and have at least two circulation channels, said channels being separated by an internal partition formed by joining opposite edges of a metal strip.

According to another aspect of the multi-fluid heat exchanger, the internal spacers extend over the entire length of the flat tubes.

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

FIG. 1 represents a schematic view of a multi-fluid heat exchanger,

FIG. 2 represents a schematic view of a detail of the multi-fluid heat exchanger showing a collecting box and flat tubes,

FIG. 3 represents a schematic view of a flat tube,

FIG. 4 represents a schematic view of a first variant of the flat tube, the flat tube containing a first internal spacer,

Figure 5 shows a schematic view of a second variant of the flat tube, the flat tube containing a second inner spacer. In these figures, the substantially identical elements bear the same references. As illustrated in FIG. 1, a multi-fluid heat exchanger 1 comprises a first fluid circuit 3 and a second liquid fluid circuit 5.

A first fluid 11 flows in the first fluid circuit 3. The first fluid 11 is for example a refrigerant. The first fluid circuit 3 is in the form of a condenser. The first fluid circuit 3 is a high pressure circuit, in which the first fluid 11 circulates at a first pressure up to 35 bar absolute. The first pressure is preferably 20 bar absolute. .

The first fluid circuit 3 comprises at least a first flat tube 7. Preferably, the first fluid circuit 3 comprises at least ten flat tubes 7.

A second liquid fluid 13 flows in the second liquid fluid circuit 5. The second liquid fluid 13 is for example water. The second liquid fluid circuit 5 is in the form of a radiator. The second liquid fluid 13 flows at a second pressure lower than the first pressure. Preferably, the second pressure is substantially atmospheric.

The second liquid fluid circuit 5 comprises at least one second flat tube 9. Preferably, the second liquid fluid circuit 5 comprises at least two flat tubes 9.

The first flat tubes 7 and the second flat tubes 9 are connected to a first common collecting box 15 and to a second common header 17 having slots (not shown) allowing the insertion of the first tubes 7 and the second tubes 9. The multi-fluid heat exchanger 1 further comprises cheeks 18a, 18b arranged parallel to the first tubes 7 and the second tubes 9 at the ends of the multi-fluid heat exchanger 1. The cheeks 18a, 18b of the multi-heat exchanger fluids 1 form a spacer between the manifolds 15, 17 to maintain a constant gap between them and facilitate the manufacture of the multi-fluid heat exchanger 1.

The first manifold 15 has a plurality of manifolds 19, 21, 23, 25 for the entry and exit of fluids into the first manifold 15. Thus the first fluid 11, coming from a first external circuit (not shown), for example an air conditioning circuit of the vehicle, enters the first manifold 15 by a first inlet pipe 19. Then, the first fluid 11 gains the second manifold 17 via the first flat tubes 7, and then returns to the first manifold 15. The first fluid 11 then leaves the first manifold 15 through the first outlet manifold 21 and thus joins the first circuit outside. When it circulates inside the multi-fluid heat exchanger 1, the first fluid 11 gives heat to a third fluid 23 which circulates between the flat tubes 7. This third fluid 23 is for example air.

Similarly, the second liquid fluid 13, coming from a second external circuit (not shown), for example a low-temperature water circuit used for cooling the vehicle electronics, enters the first header 15 by the second inlet tubing 25. Then the second liquid fluid 13 gains the second manifold 17 through the second tubes 9, and then returns to the first manifold 15. The second liquid fluid 13 then leaves the first manifold 15 by the second outlet pipe 27 and thus joins the second external circuit. When circulating inside the multi-fluid heat exchanger 1, the second liquid fluid 13 also gives heat to the third fluid 23.

According to a variant (not shown), the inlet pipes 19, 25 are carried by the first manifold 15 and the outlet pipes 21, 27 are carried by the second manifold 17 (or vice versa).

The multi-fluid heat exchanger 1 may further comprise a fluid reservoir 28 used for example for the first fluid 11. The first fluid circuit 3 is of multi-pass type, the fluid reservoir 28 is connected in series between the before last pass and the last pass of the first fluid circuit 3 via the second manifold 17

According to this example, the need in heat exchange of the second fluid fluid

13, the water is lower than that of the first fluid 11, the refrigerant. Consequently, the second liquid fluid circuit 5 comprises fewer second flat tubes 9 than the first fluid circuit 3.

By using a part of the flat tubes of the multi-fluid heat exchanger 1 to the second liquid fluid circuit 5, the performance of the heat exchange of the first fluid circuit 3 is reduced. The height hi and the length / _/ of the multi-fluid heat exchanger 1 are constrained by the space available in the front part of the vehicle. It is therefore difficult to increase the height hj or the length / _/ the multi-fluid heat exchanger 1 to compensate for the decrease in performance of the first fluid circuit 3.

However, it is possible to increase the width L _/ of the multi-fluid heat exchanger 1, for which the width L ₂ of the flat tubes 7, 9 is increased (see FIG. 3).

Referring now to Figure 2 which shows a detail of the multi-fluid heat exchanger 1. In order that the first fluid 11 and the second liquid fluid 13 do not mix, the first manifold 15 and the second manifold 17 are divided into a plurality of parts including a first part A and a second part B. The first part A is part of the first fluid circuit 3 and is reserved for the circulation of the first fluid 11. The second part B is part of the second liquid fluid circuit 5 and is reserved for the circulation of the second liquid fluid 13.

To separate the first part A of the second part B, the first and the second manifold 15, 17 (a single manifold, is visible in this figure) may for example have a double inner wall comprising a first wall 29 and a second wall 31. The first wall 29 and the second wall 31 are placed between a first slot and a second slot (not shown) of the manifolds 15, 17, the first slot receiving a first end tube 71 of the first bundle of tubes, and the second slot receiving a second end tube 91 of the second bundle of tubes.

The first inner wall 29 and the second inner wall 31 delimit a third portion C which is therefore located between the first portion A and the second portion B. This third portion C serves as a buffer between the first portion A and the second portion B. Indeed, in the event that a leak occurs for example on the first wall 29, then the first fluid 11 would flow into the third part C and not into the second part B. This allows on the one hand to avoid mixing the first and the second fluid 11, 13 which could lead to a degradation of the multi-fluid heat exchanger 1 and the vehicle. On the other hand, it avoids the pressure shock between the two fluids 11, 13, which would also degrade the multi-fluid heat exchanger 1 and the vehicle. Indeed, the first fluid 11 flows at a first pressure greater than the second circulation pressure of the second liquid fluid 13 Advantageously, the third portion C may comprise an opening 33 to the outside of the multi-fluid heat exchanger 1. Thus, the fluid 11, 13 contained in the third part C may be discharged to the outside.

In order to improve heat exchange, outer spacers 35 may be disposed between adjacent tubes 7, 9. These external spacers 35 have for example a substantially undulating shape. The peaks of the corrugations of the outer spacers 35 are in contact with the outer walls of the tubes 7, 9, for example by being brazed to the outer walls of the tubes 7, 9. The outer spacers 35 thus form a plurality of external channels through which the third fluid 23 is directed, for example by a fan (not shown). Thus the heat of the first fluid 11 and the second liquid fluid 13 is transferred to the tubes 7, 9 and the outer spacers 35, thus increasing the heat exchange surface with the third fluid 23 and thereby improving the efficiency of the heat exchange. Referring now to Figure 3 which shows a flat tube 7, 9 as used in the multi-fluid heat exchanger 1.

The flat tube 7, 9 has a first large flat face 35, and a second large flat face 37. The first large face 35 and the second large flat face 37 are parallel and connected by two small curved faces 39, 41. The flat tube 7, 9 has a height h ₂ and a width L ₂ .

In addition, a flat tube 7, 9 has an internal partition 43 forming a spacer between the two large parallel faces 35, 37. Such a flat tube 7, 9 is obtained by folding a metal strip on itself by joining two opposite edges. in order to form the internal partition 43. Thus the partition is derived from the first large planar face 35 and is facing the second large planar face 37. The internal partition 43 separates the folded flat tube 7, 9 into two channels 45, 47 of fluid circulation. The flat tube 7, 9 thus has a cross section substantially "B". A space between the internal partition 43 and the large second large flat face 37 allows the passage of an inner spacer 49, 53 (visible in Figures 4 and 5). The function of the inner spacer 49, 53 is described below.

The tube is for example made of aluminum or aluminum alloy. The internal partition 43 makes it possible to increase the mechanical strength of the folded flat tubes 7, The first fluid 11 and the second liquid fluid 13 have different characteristics which leads to different needs in the dimensioning of the flat tubes 7, 9.

As said above, the first fluid 11 flows at a first pressure up to 35 bars absolute, while the second fluid 13 flows at a second substantially atmospheric pressure. The first flat tubes 7 must therefore have a greater mechanical strength than the second flat tubes 9 in order to withstand the circulation pressure of the first fluid 11.

Referring to FIG. 4, in order to increase the mechanical strength of the first flat tubes 7, first inner dividers 49 are arranged inside the first flat tubes 7. The first internal dividers 49 extend over the entire length l ₂ of the first flat tubes 7.

These internal spacers 49 have for example a substantially undulating shape. The ridges 51 of the internal spacers 49 are in contact with the large parallel faces 35, 37 of the first flat tubes 7. The peaks 51 of the inner spacers 49 are fixed on the large parallel faces 35, 37, for example by brazing or welding. The greater the number of ridges 51 attached to the large parallel faces 35, 37 is large, and the better is the mechanical strength of the first flat tubes 7. The number of ridges 51 of the first spacer 49 is chosen to allow the first flat tube 7 to resist at the pressure of the first fluid 11.

Referring now to FIG. 5. According to the example, the mechanical strength requirements of the second flat tubes 9 are lower than those of the first flat tubes 7.

According to a variant, the second tubes 9 comprise second inner dividers 53 having a number of corrugations, and therefore ridges 55, smaller than the first internal spacers 51. The ridges 55 of the second inner spacers 53 are attached to the large parallel faces second flat tubes 9, for example by brazing or welding. The second inner spacers 53 extend over the entire length 1 ₂ of the first flat tubes 9.

According to another variant, the second tubes 9 do not include internal spacers.

The addition of internal spacers 49, 53 according to the characteristics of the first and second fluids 11, 13 makes it possible to use flat tubes 7, 9 having a similar external shape, among others an identical cross-section, the same height and the same width L2. By using a standard model of tubes 7, 9 for the first fluid circuit 3 and for the second liquid fluid circuit 5, the production of the flat tubes 7, 9 is simplified and the production costs are reduced.

In addition, the similar outer shape of the flat tubes 7, 9 allows the use of manifolds 15, 17 with similar slots. Thus, a standard model of header can be used regardless of the fluid flowing in the multi-fluid heat exchanger. In fact, the manifolds 13, 15 can also be used in a simple fluid exchanger. This further reduces the production costs of the heat exchanger.

According to another variant, only the second flat tube located at the inner end 91 of the second liquid fluid circuit 5 and the second flat tube located at the outer end 93 of the second fluid circuit 5 (in FIG. second internal dividers 53.

Indeed, the temperature of the second liquid fluid circuit 5 is higher than that of the first fluid circuit 3. The temperature of the first fluid circuit is, for example, 20 ° C., the temperature of the second liquid fluid circuit 5 is example of 70 ° C. Under the effect of heat, the second liquid fluid circuit 5 expands substantially more than the first fluid circuit 3, thus applying a stress on the first fluid circuit 3.

In order to avoid degrading the first fluid circuit 3, an inner spacer 53 is then added to the second inner end flat tube 91 of the second liquid fluid circuit 5 at the boundary between the first fluid circuit 3 and the second liquid fluid circuit 5. Thus the mechanical stress due to the expansion is applied to the inner spacer 53 and not to the first fluid circuit 3, which preserves the first fluid circuit 3.

Similarly, an inner spacer 53 may be placed in the second outer end flat tube 93 at the boundary between the multi-fluid heat exchanger 1 and the cheek 18b. Thus the transfer of the mechanical stresses due to the expansion on the cheek 18b is avoided.

It is therefore understood that by fixing first internal spacers 49 inside the first flat tubes 7 of a fluid circuit 3 at high pressure of a multi-fluid heat exchanger 1, the first flat tubes 7 are allowed to resist the pressure of the first fluid 3. Thus, it is possible to use a standard model of flat tubes 7, 9 for the first fluid circuit 3 and for the second liquid fluid circuit 5. This simplifies, on the one hand, the production of the flat tubes 7, 9. And on the other hand Part one simplifies the production of collector boxes because we can also use a standard model regardless of the type of heat exchanger. This lowers production costs.

Claims

claims

A multi-fluid heat exchanger (1) for a motor vehicle comprising:

A first high pressure fluid circuit (3) comprising at least a first flat tube (7) allowing the circulation of a first fluid (11) at a first pressure, said first flat tube (7) comprising at least a first intermediate internal (49) of corrugated form whose peaks (51) are fixed with an inner wall of the first flat tube (7),

A second liquid fluid circuit (5) comprising at least a second flat tube (9) allowing the circulation of a second liquid fluid (13) at a second pressure lower than the first pressure,

characterized in that said first flat tube (7) and said second flat tube (9) are folded tubes having a similar external shape, and in that the number of ridges (51) of the first inner spacer (49) is dimensioned to allow the first flat tube (7) to resist the pressure of the first fluid (11).

2. Multi-fluid heat exchanger (1) according to claim 1, characterized in that the first fluid circuit (3) is in the form of a condenser, and the second liquid fluid circuit (5) is produced under the shape of a radiator.

3. multi-fluid heat exchanger (1) according to one of the preceding claims, characterized in that at least a second tube (9) of the second liquid fluid circuit (5) comprises a second inner spacer (53).

4. Multi-fluid heat exchanger (1) according to claim 3, characterized in that at least a second end tube (91, 93) of the second liquid fluid circuit (5) comprises a second inner spacer (53) .

5. Multi-fluid heat exchanger (1) according to claim 4, wherein the first fluid circuit (3) and the second liquid fluid circuit (5) have different temperatures, characterized in that the second end tube interior (91) comprises a second inner spacer (53).

6. multi-fluid heat exchanger (1) according to one of claims 3 to 5, characterized in that the peaks (55) of the second inner spacers (53) are fixed with the inner wall of the second flat tubes (9).

7. multi-fluid heat exchanger (1) according to one of the preceding claims, the first flat tubes (7) and second flat tubes (9) being connected to a first common header (15) and a second header ( 17), characterized in that the first manifold (15) and the second manifold (17) each comprise a double internal wall (29,31) for separating the first fluid circuit (3) and the second fluid circuit (3). liquid fluid (5).

8. multi-fluid heat exchanger (1) according to one of the preceding claims, characterized in that the first pressure reaches up to 35 bar absolute, and the second pressure is substantially atmospheric.

9. multi-fluid heat exchanger (1) according to one of the preceding claims, characterized in that the first flat tubes (7) and the second flat tubes (9) are substantially bent tubes and have at least two channels (45, 47) of circulation, said channels being separated by an internal partition (43) formed by joining the opposite edges of a metal strip.

10. Multi-fluid heat exchanger (1) according to one of the preceding claims, characterized in that the internal spacers (49, 53) extend over the entire length (1 ₂ ) of the flat tubes (7, 9).