FR3048496A1 - HEAT EXCHANGER WITH FLEXIBLE WALL FOR THE THERMAL MANAGEMENT OF AN ELECTRIC BATTERY - Google Patents

Abstract

This heat exchanger (10) comprises a circulation channel (14) of a first heat transfer fluid (16) and an enclosure (12) in which the channel (16) is housed. The enclosure (12) comprises a flexible wall (24) forming a thermal conductor provided with an outer surface (28) intended to come into contact with a thermoregulating member (36), for example a battery or a battery module. The chamber (12) contains a second heat transfer fluid (18), the channel (14) being housed in the chamber (12) so as to allow the passage of the second heat transfer fluid (18) between an inner surface (26) of the flexible wall (24) forming a thermal conductor and the channel (14). The flexible wall (24) forming a thermal conductor makes it possible for the second heat transfer fluid (18) to move freely in the enclosure (12) and to locally deform the flexible wall (24) forming a thermal conductor so as to maximize the contact of the wall flexible (24) forming a thermal conductor with the thermoregulating member (36).

Description

Flexible wall heat exchanger for the thermal management of an electric battery.

The present invention relates to the thermal regulation of an electric battery or of an electric battery module and more particularly to a heat exchanger for the thermal management of an electric battery or an electric battery module, in particular in the automotive field .

The current trend among car manufacturers is to integrate more and more electrical energy into their vehicles, whether to move fully electric vehicles, hybrid vehicles or to provide simple assistance by means of main propulsion in order to improve the autonomy of the vehicle.

The power involved in these vehicles requires large amounts of electrical energy, which are stored in high capacity batteries designed specifically for this purpose. They are formed of elementary cells which are placed next to each other and electrically connected together to, on the one hand, provide the desired voltage and, on the other hand, generate the desired storage capacity. These elementary cells have mainly the shape of a parallelepiped plate which is equipped with contacts, on one of its faces, to receive a direct current supply or to restore the stored energy. Inside the plate is conventionally constituted by a succession of cathodes and anodes which are placed alternately and which are separated from each other by insulating sheets. The elementary cells are thus placed side by side, in a support structure, so as to form an autonomous battery module which delivers the desired voltage and which has the capacity of the sum of the capacities of its various elementary cells.

One of the major problems with electric batteries with high capacity is the management of their temperature, because their electrical behavior varies very strongly with it. If the temperature of the module is too low its capacity decreases, and if it is too high, the life of the battery is reduced, with the additional risk of short circuit and irreversible damage in the elementary cells. The temperature of the battery should therefore be maintained within an optimum temperature range of approximately 20 to 40 ° C. For this, the batteries are associated with a heating or cooling circuit, which is coupled to the vehicle conditioning system, to provide the necessary calories or frigories. In each module is thus installed an element, called cooling plate, which is connected to the general cooling circuit of the battery. It is brought into contact with the elementary cells of this module and it cools them, or heats them up, with liquid that it receives from the conditioning system and circulates in an internal circuit. FR 3,013,515 proposes a cooling plate improving the contact between this cooling plate and the elementary cells of a battery module, to provide flexibility in the design of these plates, and / or to reduce their weight and the cost.

Thus, FR 3,013,515 proposes a cooling plate forming a heat exchanger comprising a heat transfer fluid circulation channel and an enclosure in which the channel is housed.

This enclosure comprises a flexible wall forming a thermal conductor provided with an external surface intended to come into contact with a body to be thermoregulated, namely a battery module.

More particularly, the enclosure comprises two sheets of polymer such as polypropylene, forming two opposite walls of the enclosure, one of these walls being the flexible wall forming thermal conductor. The sheet of polymer allows, by its deformation, a maximum contact with the peripheral edge of the elementary cells of the battery module.

The two sheets of polypropylene are welded together around their periphery so as to form a sealed pocket, in which circulates the coolant. The sheets are furthermore welded along strips which extend along the length of the bag and which delimit between them the heat transfer fluid circulation channel.

The heat transfer fluid circulation channel is formed by the polymer sheets welded together.

However, in this type of heat exchanger, the coolant exchanges heat with the member to be thermoregulated, in particular a battery module, throughout its movement in the circulation channel, so that a difference temperature of the heat transfer fluid appears between the inlet and the outlet of the canal. This difference in temperature can cause a heterogeneity of the temperature of the body to be thermoregulated. This heterogeneity may prevent keeping the entire organ thermoregulate at an optimum temperature. The invention therefore aims to make more homogeneous exchanges of heat between the heat exchanger and the body thermoregulate along the flexible wall forming thermal conductor. For this purpose, the subject of the invention is a heat exchanger comprising a circulation channel of a first heat transfer fluid and an enclosure in which the channel is housed, this chamber comprising a flexible wall forming a thermal conductor provided with an external surface. intended to come into contact with a thermoregulatory element, for example a battery or a battery module, characterized in that the enclosure contains a second heat-transfer fluid, the channel being housed in the enclosure so as to allow the passage of the second fluid a carrier between an inner surface of the flexible wall forming a thermal conductor and the channel, and in that the flexible wall forming a thermal conductor makes it possible for the second heat transfer fluid to be able to move freely in the enclosure and to locally deform the flexible wall forming the thermal conductor. so as to maximize the contact of the flexible wall forming the thermal conductor with the thermoregulatory member.

In the heat exchanger according to the invention, the first heat transfer fluid is not in direct contact with the flexible wall forming the thermal conductor. The second heat transfer fluid serves as an intermediate fluid homogenizing the temperature in the chamber, essentially by convection, and thus ensuring a better homogeneity of the temperature of the flexible wall forming thermal conductor.

In addition, the second coolant fluid can serve as a thermal energy storage member. The thermal inertia of the second fluid may allow to continue to regulate the temperature of the thermoregulatory member when the first coolant fluid does not circulate. This allows in particular to limit the periods of circulation of the first fluid in the heat exchanger and thus to save energy.

Liquid phase change materials, in particular, can store or dissipate a large amount of heat, in the form of calories or frigories, as they change phase.

Other optional characteristics of the heat exchanger according to the invention will be specified below.

The second coolant fluid is a phase change material, such a material for storing a large amount of frigories when it changes phase, especially when passing from a liquid phase to a solid phase.

The circulation channel of the first coolant fluid is delimited by a tube.

The circulation channel of the first coolant fluid is delimited by two metal sheets assembled together, the channel being delimited by at least one recess formed in at least one of the sheets. The enclosure comprises a sheet folded so as to form two sheets of feuiile forming two opposite walls of the enclosure, one of these walls being the flexible wall forming thermal conductor. The enclosure comprises two sheets forming two opposite walls of the enclosure, one of these walls being the flexible wall forming thermal conductor.

The flexible wall forming thermal conductor is composed essentially of aluminum.

The flexible wall forming a thermal conductor is composed essentially of polymer. The enclosure comprises a local reinforcing weld locally bonding the flexible wall forming thermal conductor to the circulation channel. The enclosure comprises a filling end of the second heat transfer fluid. The subject of the invention is also a method for manufacturing a heat exchanger as defined above, characterized in that it comprises: a step of positioning the circulation channel between the two parts of sheets forming the two opposite walls of the enclosure, a step of welding portions of sheet to form a weld line separating the inside of the outside of the enclosure, a step of filling the chamber with the second heat transfer fluid, a cutting step leaf edge extending outside the enclosure.

Other optional characteristics of this process for producing the heat exchanger according to the invention will be specified below.

The method includes an additional step of cutting leaf edges extending outside the enclosure. The filling step is between a first step of welding the two sheet portions to form a first weld line locally separating the inside of the outside of the enclosure and a second step of welding the two sheet portions to forming a second weld line separating locally the inside and the outside of the enclosure extending the first weld line, the second weld line forming an opening having allowed the filling of the enclosure by the second heat transfer fluid.

The enclosure is filled after a step of welding the two sheet portions to form a weld line separating the interior of the outside of the enclosure and wherein the filling of the enclosure with the second heat transfer fluid is done by the filling tip. The invention will be better understood on reading the following description given solely by way of example and with reference to the appended drawings in which: FIG. 1 is a vertical sectional view of an assembly comprising a module of FIG. battery in contact with a heat exchanger according to a first embodiment of the invention; Figure 2 is a view similar to that of Figure 1 of the heat exchanger according to the first embodiment of the invention, before introduction of the battery module; Figure 3 is a top view of the heat exchanger shown in Figure 1; Figure 4 is a sectional view along line IV - IV of Figure 3; Figures 5 and 6 are views similar to those of Figures 3 and 4 of a heat exchanger according to a second embodiment of the invention; Figure 7 is a view similar to that of Figure 2 showing a heat exchanger according to a third embodiment of the invention; Figures 8 and 9 are views similar to that of Figure 3 respectively illustrating two of the manufacturing steps of the heat exchanger according to the first embodiment of the invention.

FIGS. 1 to 4 show a heat exchanger 10 according to a first embodiment of the invention. The heat exchanger 10 comprises an enclosure 12 and a circulation channel 14 of a first coolant 16. The circulation channel 14 is housed in the enclosure 12. A second heat transfer fluid 18 is housed in the enclosure 12 in the volume not occupied by the circulation channel 14. The enclosure 12 comprises two sheets 22 welded at their edges by a weld line 23 forming a closed circuit (see FIGS. 3 and 4). This weld line 23 is hermetic and separates the outside of the interior of the enclosure 12. The two welded sheets 22 form two opposite walls 24 of the enclosure 12. Each of these walls is a flexible wall 24 forming a thermal conductor .

Each flexible wall 24 forming a thermal conductor comprises an inner surface 26 delimiting the internal volume of the enclosure 12 and an opposite outer surface 28. The inner surface 26 is turned towards the circulation channel 14 while the outer surface 28 is turned from the worm the outside of the enclosure 12.

It will be noted that the channel 14 is housed in the chamber 12 so as to allow the passage of the second heat transfer fluid 18 between the inner surface 26 of the flexible wall 24 forming a thermal conductor and the channel 14.

The flexible walls 24 forming a thermal conductor are designed in such a way that they fold and deform easily. An appropriate flexibility of the walls 24 can be obtained by those skilled in the art by choosing a suitable material and dimensions.

The circulation channel 14 is delimited by a relatively rigid tube 30, made of conventional material, extending from an inlet 32 of the circulation channel to an outlet 34 of the circulation channel 14. The circulation channel 14 follows a boustrophedon path . The inlet 32 and the outlet 34 of the circulation channel 14 open out of the enclosure 12.

As can be seen in FIG. 3, local reinforcing welds 35 locally connect at least one wall 24 of the enclosure 12 to the circulation channel 14. These local welds 35 are positioned in such a way that they do not prevent the circulation of the second coolant 18 throughout the chamber 12. Alternatively, these local welds 35 are not present.

As can be seen in FIG. 1, the heat exchanger 10 forms a cooling plate intended to be brought into contact with a thermoregulating member 36. The contact with the member to be heat-regulated 36 is on the outer surface 28 a flexible wall 24 forming thermal conductor of the heat exchanger 10. The thermoregulating member 36 is, in the example described, a conventional battery module. The surface 38 of the thermoregulating member 36 which is brought into contact with the flexible wall 24 forming a thermal conductor is not rigorously flat. In particular, this surface 38 may have recesses due to the imprecise positioning of elementary cells of the module 36.

The flexible wall 24 forming a thermal conductor placed against the member to thermoregulate 36, is deformed and matches the irregularities of the surface 38 of the member to thermoregulate 36. This deformation is possible because the wall 24 forming a thermal conductor is flexible and the second heat transfer fluid 18 can move freely in the chamber 12 as a function of deformations of the flexible wall 24.

Thus, the flexible wall 24 forming a thermal conductor makes it possible for the second heat-transfer fluid 18 to move freely in the chamber 12 by locally deforming this flexible wall 24 forming a thermal conductor so as to maximize the contact of the flexible wall 24 forming a thermal conductor with the thermoregulating member 36.

The flexible wall 24 forming a thermal conductor is made of thermally conductive material and has suitable properties for this wall 24 to be flexible. The flexible wall 24 forming a thermal conductor may consist essentially of aluminum or essentially of polymer, or even a combination of aluminum and polymer.

According to a first possible configuration of the operation of the heat exchanger 10, the first heat transfer fluid 16 circulates in the circulation channel 14 from the inlet 32 to the outlet 34 of the circulation channel. During this circulation, the first heat transfer fluid 16 exchanges heat with the second coolant 18. Thus the temperature of the second heat transfer fluid 18 is regulated. The second coolant 18 exchanges heat with the thermoregulating member 36 through the flexible wall 24 forming a thermal conductor. Thus the temperature of the thermoregulating member 36 and regulated.

According to a second possible configuration of the operation of the heat exchanger, the thermal inertia of the second heat transfer fluid 18 is used without circulating the first heat transfer fluid 16 in the channel. Thus, the thermal inertia of the second heat transfer fluid 18 is used to accumulate calories or colds. This energy storage makes it possible to limit the periods of circulation of the first fluid 16 in the heat exchanger 10, and thus to save energy. During periods when the first heat transfer fluid 16 does not circulate, the second heat transfer fluid 18 continues for a certain time, to regulate the temperature of the thermoregulating member 36.

It is in particular possible to use a second coolant 18 selected from phase change materials to achieve this thermal energy storage function. A phase change material, noted MCP thereafter, is a material used to store or restore a large amount of energy during its phase change. The energy exchanged during a phase change of a material is generally much greater than that exchanged during a simple temperature variation of this material.

When using a MCP, as a second heat transfer fluid 18, for cooling a battery, the cooling of the second heat transfer fluid 18 causes it to solidify. Consequently, a PCM which, when it passes into the solid phase, remains relatively fluid to allow appropriate deformation of the enclosure, will preferably be chosen.

When stopping the flow of the first coolant 16, the second heat transfer fluid 18 in the form of a PCM can absorb a large amount of heat, by liquefying, and thus continue to regulate the temperature of the body to thermostated.

Without stopping circulation of the first heat transfer fluid 16, if the member thermoregulate momentarily overheating, the MCP can change phase to absorb some of the heat. The MCP then acts in support of the first heat transfer fluid.

A process according to the invention for the manufacture of the heat exchanger 10 according to the first embodiment will be described below, with particular reference to FIGS. 8 and 9.

First, the circulation channel 14 is positioned between two portions of raw sheets 22B intended to form the flexible walls 24 forming a thermal conductor (see FIG. 8).

Then, the two portions of raw sheets 22B are welded together to form the weld line 23 separating the inside from the outside of the enclosure 12 (see FIG. 9).

If necessary, cut the edges of the raw sheets 22B extending outside the chamber 12 to form the sheets 22 shown in Figures 1 to 4.

According to a first embodiment of the manufacturing process of the heat exchanger 10, a step is performed for filling the chamber 12 with the second heat transfer fluid 18 in the following manner. The filling step is between a first step of welding the two parts of raw sheets 22B to form a first weld line 23A, locally separating the inside of the outside of the enclosure 12, and a second welding step two blank sheet portions 22B to form a second weld line 23B, locally separating the interior and exterior of the enclosure 12. The second weld line 23B extends the first weld line 23A to form the weld line 23.

The second weld line 23B closes a temporary opening through which the step of filling the chamber 12 with the second heat transfer fluid has been performed.

A second embodiment of the heat exchanger according to the invention will be described below, with reference to FIGS. 5 and 6. In these Figures 5 and 6, the elements similar to those of the preceding figures are designated by identical references.

In this embodiment, the enclosure 12 comprises a folded sheet 40 so as to form two sheets of sheet 42 which form the two opposite flexible walls 24 of the enclosure. These two pieces of sheet 42 are welded together by their edges by a hermetic sealing line 43 separating the outside of the inside of the enclosure 12. The enclosure 12 is provided with a filling tip 44 which allows filling the chamber 12 with the second heat transfer fluid 18.

A process according to the invention for the manufacture of the heat exchanger 10 according to the second embodiment will be described below.

First, a raw sheet is folded so as to obtain two sheets of sheet intended to form the two flexible walls 24 forming a thermal conductor.

Then, the circulation channel 14 is positioned between the two sheets of raw sheet intended to form the flexible walls 24.

Next, the two raw-sheet webs are welded to form the weld line 43 separating the inside from the outside of the enclosure 12.

Where appropriate, edges of the raw sheet extending outside the enclosure 12 are cut to form the sheet sections 42 shown in FIGS. 5 and 6. In contrast to the method according to the first embodiment according to a second embodiment of the method of manufacturing the heat exchanger 10, the step of filling the chamber 12 with the second heat transfer fluid 18 is carried out in the following manner.

In this case, the filling of the chamber 12 is done after the step of welding the two sheets of sheet to form the weld line 43 separating the inside of the outside of the enclosure. Indeed, the filling of the chamber 12 with the second heat transfer fluid 18 is done by the filling tip 44.

In a third embodiment of the heat exchanger 10, shown in FIG. 7, the circulation channel 14 can be formed from two metal sheets 46 assembled together. At least one recess 47 is formed in one of the two relatively rigid sheets 46 so as to form the circulation channel 14.

Claims (14)

1. Heat exchanger (10) comprising a circulation channel (14) of a first coolant (16) and an enclosure (12) in which the channel (16) is housed, this enclosure (12) comprising a flexible wall Heat-conducting member (24) having an outer surface (28) for contacting a thermoregulator (36), for example a battery or a battery module, characterized in that the enclosure (12) contains a second coolant (18), the channel (14) being housed in the chamber (12) so as to allow the passage of the second heat transfer fluid (18) between an inner surface (26) of the flexible wall (24) forming thermal conductor and the channel (14), and in that the flexible wall (24) forming a thermal conductor allows the second heat transfer fluid (18) to move freely in the enclosure (12) and locally deform the flexible wall (24). forming a thermal conductor so as to maximize the contact of the flexible wall (24) ) forming a thermal conductor with the thermoregulating member (36). 2. heat exchanger (10) according to claim 1 wherein the second heat transfer fluid (18) is a phase change material, such material for storing a large amount of frigories when it changes phase, especially when it goes from a liquid phase to a solid phase. 3. Heat exchanger (10) according to claim 1 or 2 wherein the circulation channel (14) of the first heat transfer fluid (16) is delimited by a tube (30). 4. heat exchanger (10) according to claim 1 or 2 wherein the channel (14) for circulating the first heat transfer fluid (16) is delimited by two metal sheets (46) assembled together, the channel (14) being defined by at least one recess (47) in at least one of the sheets (46). The heat exchanger (10) according to any one of claims 1 to 4, wherein the enclosure (12) comprises a folded sheet (40) so as to form two sheets of sheet (42) forming two walls (22). ) of the enclosure (12), one of these walls (22) being the flexible wall (24) forming a thermal conductor. 6. heat exchanger (10) according to any one of claims 1 to 4, wherein the enclosure (12) comprises two sheets (18) forming two walls (22) opposite the enclosure (12), the one of these walls (22) being the flexible wall (24) forming a thermal conductor. 7. Heat exchanger (10) according to any one of claims 1 to 6, wherein the flexible wall (24) forming a thermal conductor is composed essentially of aluminum. 8. heat exchanger (10) according to any one of claims 1 to 6, wherein the flexible wall (24) forming a thermal conductor is composed essentially of polymer. 9. heat exchanger (10) according to any one of claims 1 to 8, wherein the enclosure (12) comprises a local weld (35) reinforcement locally bonding the flexible wall (24) forming a thermal conductor to the channel. circulation (14). 10. Heat exchanger (10) according to any one of claims 1 to 9, wherein the enclosure (12) comprises a filling tip (44) of the second heat transfer fluid (18). 11. A method of manufacturing a heat exchanger (10) according to claim 5 or 6, characterized in that it comprises: a step of positioning the circulation channel (14) between two parts of sheet intended to form the two opposing walls (24) of the enclosure, a step of welding these sheet portions to form a weld line (48) separating the interior from the outside of the enclosure (12), a step of filling the enclosure (12) with the second heat transfer fluid (18). The manufacturing method according to claim 11, further comprising a sheet cutting step (49) extending outside the enclosure (12). 13. The manufacturing method according to claim 11 or 12, wherein the filling step is between a first step of welding the two sheet portions to form a first weld line (23A) separating locally the interior of the outside the enclosure (12) and a second step of welding the two sheet portions to form a second weld line (23B) locally separating the interior and exterior of the enclosure (12) extending the first line of welding (23A), the second weld line forming an opening having allowed the filling of the enclosure by the second heat transfer fluid. 14. The manufacturing method according to claim 11 or 12, a heat exchanger (10) according to claim 10, wherein the filling of the enclosure (12) is after a step of welding the two parts of the sheet to forming a weld line (43) separating the inside from the outside of the enclosure (12) and in which the filling of the enclosure (12) with the second heat transfer fluid (18) is done by the end of filling (44).