WO2018185410A1

WO2018185410A1 - Heat exchange device for motor vehicle

Info

Publication number: WO2018185410A1
Application number: PCT/FR2018/050803
Authority: WO
Inventors: Kamel Azzouz; Cédric DE VAULX
Original assignee: Valeo Systemes Thermiques
Priority date: 2017-04-03
Filing date: 2018-03-30
Publication date: 2018-10-11
Also published as: FR3064735A1; DE112018001846T5; FR3064735B1

Abstract

The subject of the invention is a heat exchange device for a motor vehicle, comprising a heat exchange surface (3) between a first fluid and a second fluid, said surface (3) being equipped with a substrate (4) and with a layer (5) consisting of a material based on a shape-memory alloy applied on the substrate, referred to as shape-memory layer, the shape-memory alloy having an austenite-martensite phase transition and an associated phase transition temperature being within a range of temperatures of one of the first fluid and of the second fluid in an operating state of the heat exchange device, the substrate (4) having a Young's modulus greater than a Young's modulus of the shape-memory layer (5) and an expansion coefficient of the substrate (4) different from an expansion coefficient of the shape-memory layer (5).

Description

THERMAL EXCHANGE DEVICE FOR MOTOR VEHICLE

The invention relates to a heat exchange device for a motor vehicle, comprising at least one heat exchange portion delimiting a heat exchange surface between a first fluid and a second fluid.

The heat exchange surface is generally defined for a specific engine speed, said full load, which is only rarely or never reached during the life of the vehicle.

As a result, the heat exchange surface is oversized relative to the normal conditions of use, which has the effect of reducing the efficiency of a thermodynamic loop associated with the heat exchange device (since the exchange surface oversized thermal causes a significant loss of load) and increase the energy consumption of the motor vehicle.

The object of the invention is to overcome these disadvantages.

For this purpose, the invention relates to a heat exchange device for a motor vehicle, comprising a heat exchange surface between a first fluid and a second fluid, said heat exchange surface being provided with a substrate and a a layer made of a shape memory alloy material applied to the substrate, said shape memory layer, the shape memory alloy having a phase transition between austenite phase and a martensite phase and an associated phase transition temperature within a temperature range of one of the first fluid and the second fluid in an operating state of the heat exchange device, the substrate having a Young's modulus greater than a Young's modulus of the shape memory layer and a coefficient of expansion of the substrate different from a coefficient of expansion of the shape memory layer.

Thanks to the device according to the present invention, the memory layer of form undergoes a phase transition as a function of the temperature of one of the fluids during use of the heat exchange device, which, due to the rearrangement of the crystal lattice and the mentioned criteria relating to the Young's modulus and coefficient of expansion thermal, causes a change in the heat exchange surface, making it adaptable to temperature variations of the engine of the motor vehicle.

According to another characteristic of the invention, the shape memory alloy comprises nickel, and / or titanium, and / or copper, and / or aluminum, and / or carbon monoxide, and / or or manganese, and / or styrene maleic anhydride (SMA) plastic.

According to another characteristic of the invention, the substrate is metallic, for example based on aluminum.

According to another characteristic of the invention, the Young's modulus of the substrate is of the order of or greater than 60 GPa.

According to another characteristic of the invention, the shape memory layer has a thickness between 2 μιη and 200 μιτι, preferably between 20 μιη and 40 μιτι.

According to another characteristic of the invention, the substrate has a thickness of the order of or greater than 50 μιτι.

According to another characteristic of the invention, the transition temperature is between 80 ° C and 100 ° C, for example between 80 ° C and 95 ° C, or between 40 ° C and 60 ° C.

According to another characteristic of the invention, the coefficient of thermal expansion of the substrate is less than or equal to a value of the order of 75% of the thermal expansion coefficient of the shape memory layer or greater than or equal to 125% of the coefficient of thermal expansion of the shape memory layer.

According to another characteristic of the invention, the memory layer of shape is discontinuous so as to form a plurality of shape memory elements.

According to another characteristic of the invention, the shape memory layer is at least one fin louver and / or at least one fin and / or at least one turbulator.

The subject of the invention is also a method for manufacturing a heat exchange device, the device comprising a heat exchange surface between a first fluid and a second fluid, the method comprising a step of producing a substrate and a step of depositing on the substrate a layer made of a material based on a shape memory alloy, called a shape memory layer, the shape memory alloy having a phase transition between a phase austenite and a martensite phase and an associated phase transition temperature within a temperature range of one of the first fluid and the second fluid in an operating state of the heat exchange device, the substrate having a Young's modulus greater than a Young's modulus of the shape memory layer and a coefficient of expansion of the substrate being different from a coefficient of expansion of the shape memory layer .

According to another characteristic of the invention, the method comprises a step of heating the substrate and the shape-memory layer at a temperature greater than the phase transition temperature, called the recrystallization step, followed by a cooling step of the substrate and the shape memory layer at a temperature below the phase transition temperature.

According to another characteristic of the invention, the step of depositing the shape memory layer comprises a step of depositing a plurality of shape memory elements, the method further comprising a step of cutting the edges of the shape memory layer. each shape memory element so that each stack of shape memory element and substrate is at less partially disjointed from the substrate.

Other features and advantages of the invention will become apparent on reading the description which follows. This is purely illustrative and should be read in conjunction with the attached drawings in which:

- Figure 1 illustrates a profile of a heat exchange device according to the present invention for a first temperature, said low temperature;

FIG. 2 illustrates a profile of the heat exchange device of FIG. 1 for a second temperature, higher than the low temperature, and said high temperature;

FIG. 3 illustrates a view from above of a part of the heat exchange device according to one embodiment of the invention;

- Figures 4 and 5 illustrate a profile of the device of Figure 3 respectively at low temperature and high temperature;

- Figures 6 and 7 illustrate a method according to the present invention for the manufacture of the heat exchange device of Figure 3;

- Figures 8 and 9 illustrate a shutter according to the present invention respectively at low temperature and high temperature;

- Figures 10 and 1 1 illustrate a fin according to the present invention respectively low temperature and high temperature; and

- Figures 12 and 13 illustrate a turbulator according to the present invention respectively low temperature and high temperature.

Heat exchange device

The invention relates to a heat exchange device for a motor vehicle, referenced 1 in the figures. The heat exchange device comprises at least one heat exchange portion 2 delimiting a heat exchange surface 3 between a first fluid and a second fluid. The first fluid may be ambient air for example, and the second fluid may be a coolant or water.

Portion 2 comprises a substrate 4 and a layer made of a material based on a shape memory alloy applied to the substrate, called a shape memory layer, and referenced 5 in the figures.

The substrate 4 is advantageously metallic, and preferably aluminum.

The shape memory layer 5 is a thin layer, that is to say having a thickness of between 2 μιη and 200 μιτι, preferably between 20 μιτι and 40 μιτι.

The substrate 4 has a thickness greater than the shape memory layer 5, advantageously of the order of or greater than 50 μιτι.

The alloy constituting the shape memory layer 5 has a phase transition between an austenite phase and a martensite phase.

The shape memory alloy advantageously comprises nickel, and / or titanium, and / or copper, and / or aluminum, and / or carbon monoxide, and / or manganese, and / or styrene maleic anhydride (SMA) plastic.

An associated phase transition temperature, denoted Tp, is within a temperature range of one of the first fluid and the second fluid in an operating state of the heat exchange device 1.

By operating state of the heat exchange device is meant that the heat exchange device works under conditions of use in the motor vehicle, with the first and second fluids circulating in the device 1 at the temperatures provided. Thus, depending on the temperature of the fluid, the shape memory layer is likely to undergo a phase transition, and to be in either the austenite phase or the martensite phase.

The phase transition temperature can be adapted according to the composition of the shape memory layer 5.

Advantageously, the transition temperature is between 80 ° C and 100 ° C, for example between 80 ° C and 95 ° C, or between 40 ° C and 60 ° C.

The temperature range between 80 ° C and 100 ° C ensures that the device 1 is suitable for a high temperature radiator application.

The temperature range between 40 ° C and 60 ° C ensures that the device 1 is suitable for a low temperature radiator application.

The device 1 is such that the substrate 4 has a Young's modulus greater than a Young's modulus of the shape memory layer 5 and a coefficient of expansion of the substrate 4 different from a coefficient of expansion of the shape memory layer 5.

The difference in coefficient of expansion makes it possible to induce a bimetallic effect, allowing a curvature of the shape memory layer 5 on the substrate 4, as will be detailed later. The difference in expansion coefficients between the substrate 4 and the shape memory layer 5 thus ensures that a stress is applied to the shape memory alloy, so as to allow the austenite-martensite phase transition.

The Young's modulus of the substrate 4 greater than the Young's modulus of the shape memory layer 5 (in particular greater than the Young's modulus of the shape memory layer in its martensite phase) also makes it possible to force the bimetal to return to a flat shape when the shape memory layer changes phase again.

As can be seen in FIG. 1, at low temperature, that is to say at a temperature below the phase transition temperature Tp, the shape-memory layer 5, in its martensite phase, has a generally flat shape, placed on the substrate 4.

As can be seen in FIG. 2, at high temperature, that is to say at a temperature above the phase transition temperature Tp, the shape memory layer 5, in its austenite phase, is positioned at a distance from the substrate 4.

Thus, the heat exchange surface at high temperature is greater than the heat exchange surface at low temperature, the additional heat exchange area provided by the shape memory layer contributing to increase heat exchange in addition to the area of the substrate.

Therefore, in a low load engine speed, corresponding to a low temperature, lower than the temperature Tp, the heat exchange surface has a small value area, reducing the pressure losses.

In a high load engine regime, corresponding to a high temperature, higher than the temperature Tp, the heat exchange surface has a larger value area, allowing better cooling performance, and thus optimum operation of the motor vehicle.

Advantageously, the Young's modulus of the substrate 4 is of the order of or greater than 60 GPa, in particular if it is based on aluminum.

As already indicated, the coefficient of thermal expansion of the substrate 4 is strictly greater or less than the coefficient of thermal expansion of the shape memory layer 5.

Preferably, the coefficient of thermal expansion of the substrate 4 is less than or equal to a value of the order of 75% of the thermal expansion coefficient of the shape memory layer 5 or greater than or equal to 125% of the coefficient of thermal expansion. of the shape memory layer 5. As illustrated in FIG. 3, the shape memory layer 4 may be discontinuous so as to form a plurality of shape memory elements 6.

For example, each shape memory element 6 may have a generally trapezoidal shape. According to other possible embodiments, the shape memory elements can take any other suitable form, such as a rectangular or semicircular shape.

As shown in Figure 3, each trapezium has a large base 7 and a small base 8, opposite and parallel.

The large base 7 and the small base 8 are connected to one another by two slightly rounded sides 9.

Trapezes 6 are isosceles on the embodiment illustrated in FIG.

3.

In FIG. 3, the shape memory elements 6 are aligned in a band 10.

As is also apparent from FIG. 3, the shape memory elements 6 follow each other in the band 10 so that the large base 7 of one of the shape memory elements 6 faces the large base 7 of the shape memory element 6 following in the band 10.

Similarly, the small base 8 of one of the shape memory elements 6 faces the small base 8 of the shaped element 6 preceding it in the strip 10.

In Figure 3, the shape memory elements 6 are of identical thickness, which ensures that the shape memory elements undergo phase transitions at the same temperature.

According to a variant not illustrated, the shape memory elements have different thicknesses. In this case, the shape memory elements have different phase transitions. As can be seen in FIG. 3, each shape memory element 6 is bordered by a blank 1 1.

The cut 1 1 delimits the small base 8 and the sides 9 of each shape memory element 6. The cutout 1 1 is also made at least partly in the thickness of the substrate 4, so as to release a portion 4 '( see FIG. 5) of the substrate on which the shape memory element 6 is applied.

As can be seen in FIG. 4, a profile at a temperature lower than the transition temperature Tp of the entire substrate 4 and of the shape memory layer 5 is flat.

At this low temperature, each shape memory element 6 is in the martensite phase. In this phase, each shape memory element is plane, placed on the substrate 4.

FIG. 5 illustrates a profile with a temperature greater than the transition temperature Tp of the whole of the substrate 4 and of the shape memory layer 5.

At this high temperature, each shape memory element 6 is in the austenite phase. In this phase, each shape memory element stack 6 with the substrate 4 curves, so that the shape memory element 6 raises at least the portion 4 'of the substrate.

Due to the cut 1 1, the small base 8 rises while the large base 7 (which has not been cut from the substrate) remains on the substrate 4, causing the curvature of the sides 9 between the two bases 7 and 8.

Two adjacent shape memory elements 6 have symmetrical profiles relative to a z direction orthogonal to the band 10.

Thanks to the detachment of the elements 6 of the substrate 4, the high temperature exchange surface is greater than the low temperature heat exchange surface, the area of the substrate part 4 'peeled off and the area of each shape memory element contributing to the heat exchange.

The substrate 4 takes several forms. According to a first possible alternative, the substrate is formed by a wall of the heat exchange device, in particular if the wall is made of aluminum, on which the shape memory layer 5 is applied.

According to a second alternative, the substrate may be an additional substrate which is soldered (by brazing for example when the substrate is based on aluminum) or adhered to at least a part of the heat exchange device.

Manufacturing process

The invention also relates to a method of manufacturing the heat exchange device 1.

The method comprises a step of producing the substrate 4.

In FIG. 6, the substrate 4 is a metal strip consisting of an alloy based on aluminum.

Of course, the manufacturing process is not limited to this type of alloy and any metal substrate may optionally be used.

The manufacturing method also comprises a step of depositing on the substrate 4 of the shape memory layer 5.

The deposition can be carried out by a known thin film deposition method, for example of the physical type (physical vapor phase deposition, plasma, epitaxy), chemical (chemical vapor deposition, autocatalytic deposition, often called "electroless"), or electrochemical (electroplating).

To form the shape memory elements 6, the deposition of the alloy is performed by means of a mask, which makes it possible to delimit the application surface of the shape-memory layer 5 on the substrate, in particular to form each trapezium of shape-memory elements 6, as illustrated in FIG. 7 .

The manufacturing method comprises a step of heating the substrate 4 and the shape memory layer 5 at a temperature greater than the phase transition temperature Tp, called the recrystallization step, followed by a step of cooling the substrate 4 and of the shape memory layer 5 at a temperature below the phase transition temperature Tp.

The heating step under stress, the stress being applied by the substrate 4, makes it possible to show the martensite, in order to initiate the shape memory effect.

For example, it is heated to a temperature greater than 500 ° C., for example of the order of 600 ° C. In the context of a brazed radiator type heat exchange device, this step may for example be performed during brazing of the radiator.

Then the cooling makes it possible to find a flat profile of the elements with memory of form 6.

The method comprises a step of forming the blank 1 1 of each shape memory element 6.

The cut 1 1 follows the sides 9 and the small base 8, as already indicated.

The cutting step can take place before the recrystallization step, but it is preferable that it be subsequent to the recrystallization step, to avoid any deformation.

Preferably, during the cutting step, the shape memory layer 5 is cut with at least a portion 4 'of the thickness of the substrate to which it is applied. applications

As can be seen in FIGS. 8 and 9, the shape memory layer 5 may be at least one fin louver 12 of the heat exchange device 1.

As can be seen in FIGS. 10 and 11, the shape memory layer 5 may be at least one fin.

In the embodiment illustrated in FIGS. 10 and 11, the shape memory elements 6 are applied to the walls of the heat-exchange tubes 15, so as to form fins for heat exchange between the two fluids. .

In this example, the shape memory elements are applied to the outer walls of the tubes. However, according to another possible embodiment, the shape memory elements can be applied to the inner walls of the tubes.

Advantageously, the substrate 4 and the shape memory layer 5 are soldered to a tube wall 15.

It should be noted that, in this application, the coefficient of expansion of the substrate is strictly greater than the expansion coefficient of the shape memory layer, and preferably greater than or equal to 125% of the thermal expansion coefficient of the memory layer. of form.

As seen in Figures 12 and 13, the shape memory layer 5 is at least one fluid flow turbulator.

In the embodiment illustrated in FIGS. 12 and 13, the shape memory elements 6 form circular arcs inside the tube 15, and thus disrupt the flow of fluid inside the tube when the transition temperature Tp is exceeded by one of the first and second fluids.

Of course, the invention is not limited to this embodiment, and the turbulators 6 can be configured to take any suitable form (sinusoid, nipple, slot, etc.).

Advantages

As can be seen from the foregoing description, thanks to the invention, the pressure drops on the hot and cold fluid side can be reduced when the operating point does not require maximum thermal performance. This greatly improves the overall performance of the heat exchanger.

In addition, in the examples illustrated above, the shape memory layer is applied only to the areas that will have an additional heat exchange role at high temperature, which allows a substantial saving of shape memory material by relative to a shape memory material that would be applied more widely over the entire exchanger, or at least over the entire substrate.

Claims

1. A thermal exchange device for a motor vehicle, comprising a heat exchange surface (3) between a first fluid and a second fluid, said heat exchange surface (3) being provided with a substrate (4) and a layer (5) consisting of a shape memory alloy material applied to the substrate, said shape-memory layer, the shape-memory alloy having a phase transition between an austenite phase and a phase martensite and an associated phase transition temperature within a temperature range of one of the first fluid and the second fluid in an operating state of the heat exchange device, the substrate (4) having a Young's modulus greater than a Young's modulus of the shape memory layer (5) and a coefficient of expansion of the substrate (4) being different from a coefficient of expansion of the shape memory layer (5).

2. Heat exchange device according to the preceding claim, wherein the shape memory alloy comprises nickel, and / or titanium, and / or copper, and / or aluminum, and / or monoxide. of carbon, and / or manganese, and / or styrene maleic anhydride (SMA) plastic.

3. heat exchange device according to one of the preceding claims, wherein the substrate (4) is metallic, for example based on aluminum.

4. heat exchange device according to one of the preceding claims, wherein the Young's modulus of the substrate (4) is of the order of or greater than 60 GPa.

5. Heat exchange device according to one of the preceding claims, wherein the transition temperature is between 80 ° C and 100 ° C, for example between 80 ° C and 95 ° C, or between 40 ° C and 60 ° C ° C.

6. Heat exchange device according to one of the preceding claims, wherein the coefficient of thermal expansion of the substrate. (4) is less than or equal to a value of the order of 75% of the coefficient of thermal expansion of the shape memory layer (5) or greater than or equal to 125% of the coefficient of thermal expansion of the memory layer of form (5).

7. Heat exchange device according to one of the preceding claims, wherein the shape memory layer (5) is discontinuous so as to form a plurality of shape memory elements (6).

8. heat exchange device according to one of the preceding claims, wherein the shape memory layer is at least one fin louver and / or at least one fin and / or at least one turbulator.

9. A method of manufacturing a heat exchange device, the device comprising a heat exchange surface (3) between a first fluid and a second fluid, the method comprising a step of producing a substrate (4) and a step of depositing on the substrate (4) a layer (5) made of a material based on a shape memory alloy, called a shape memory layer, the shape memory alloy having a transition phase between an austenite phase and a martensite phase and an associated phase transition temperature within a temperature range of one of the first fluid and the second fluid in an operating state of the heat exchange device, the substrate ( 4) having a Young's modulus greater than a Young's modulus of the shape memory layer (5) and a coefficient of expansion of the substrate (4) different from a coefficient of expansion of the shape-memory layer (5) .

10. The manufacturing method according to the preceding claim, wherein the step of depositing the shape memory layer (5) comprises a step of depositing a plurality of shape memory elements (6), the method comprising in addition, a step of at least partial cutting of edges (8, 9) of each shape memory element (6).