WO2018167382A1 - Heat exchanger and thermal regulation device for at least one electrical energy storage element - Google Patents

Abstract

The invention concerns a heat exchanger (4) suitable for thermal regulation of at least one electrical energy storage element (3), in particular for a motor vehicle, comprising an assembly by superposition of a first plate (41) and a second plate (42) delimiting a circuit for circulation of a heat transfer fluid, said second plate (42) being intended to come into thermal contact with said at least one electrical energy storage element (3). According to the invention, said first plate (41) is made from a composite phase-change material comprising at least a first phase-change material and at least a second material having a structure which forms a support matrix for the first phase-change material.

Description

 Heat exchanger and thermal control device of at least one electrical energy storage element

1. Domain

 The field of the invention is that of the thermal regulation of one or more electrical energy storage elements equipping a motor vehicle whose propulsion is provided in whole or in part by an electric motor.

2. Prior Art

 The thermal regulation of the battery, particularly in the automotive field and even more particularly in the field of electric and hybrid vehicles, is a major problematm.

 The temperature of the battery must remain between. 20 ° C and 40 ° C to ensure reliability, battery life, and vehicle performance, while optimizing battery life. Indeed, when the battery is subjected to temperatures too cold, its autonomy decreases strongly. Conversely, when it is subjected to too high temperatures, there is a risk of thermal runaway up to the destruction of the battery.

 In electric or hybrid vehicles, the battery generally comprises a plurality of electric energy storage cells. These energy storage cells are positioned in a protective box and form, with this housing, what is called a battery pack.

 In order to regulate the temperature of the battery, it is known to use a thermal regulation device. The thermal regulation device comprises a heat exchanger positioned directly in contact with the battery at the bottom of the protective housing and traversed by a coolant, or Indirectly in contact with the battery in the case of an exchanger placed outside the pack drums.

 The heat transfer fluid can thus absorb the heat emitted by each battery to cool them or as needed, it can bring him heat if .the temperature of the battery is insufficient for its proper operation.

The heat transfer fluids generally used are liquids such as, for example, water. Patent document WO2010012772 discloses a heat exchanger consisting of two superimposed plates, between which, heat transfer fluid circulation channels are formed.

 Such a heat exchanger has several disadvantages.

 Firstly, such a heat exchanger is effective only when it is supplied with heat transfer fluid via a compressor or a pump. The permanent activation of this compressor or this pump during the entire phase of thermal regulation therefore generates a surplus of energy consumption (fuel or electricity) not negligible.

 Secondly, such a heat exchanger is not suitable for mulching localized heating, so-called "hot spots" that may occur within the batteries in the course of their implementation. Such overheating, when they are too large, causes degradation of the performance of the batteries, or even their damage.

 In this context, the present invention aims to provide an improved heat exchanger, to solve the aforementioned drawbacks, while being lightweight, compact, and easily assembled.

3. Summary

 The invention proposes for this purpose a heat exchanger adapted for the thermal regulation of at least one electrical energy storage element, in particular for a motor vehicle, comprising an assembly by superposition of a first plate and a second plate delimiting a flow circulating a heat transfer fluid, said second plate being intended to come into thermal contact with said at least one electrical energy storage element.

 According to the invention, said first plate is formed of a composite phase-change material comprising at least a first phase change material and at least a second material whose structure forms a support matrix of the first phase-change material .

In the remainder of the description, the notion of "thermal regulation" refers both to the cooling and the heating of a battery and / or a set of electric batteries, referred to as the "electrical energy storage element".

 A heat exchanger according to the invention comprises an assembly of. two superimposed plates.

 The first of these plates comprises a phase change material

(MCP) which in a known manner in the ground is adapted to store and restore thermal energy and in which is formed the coolant passage circuit.

 The second plate is secured to the first so as to form a sealed circuit passage of the heat transfer fluid.

 Such a phase change material has the ability to change physical state between a solid phase and a liquid phase, within a restricted temperature range. A phase change material is characterized in particular by its phase change temperature, or melting temperature, as well as SB latent phase change heat, that is to say the amount of energy that can be stored or transferred by simple change of state, while maintaining a constant temperature.

 With respect to the first plate, this phase change material is embedded in a carbon fiber matrix, for example, allowing the first plate to remain rigid during phase changes.

 Such a composite phase-change material has the first advantage of being particularly light. Its integration within the first plate makes it possible to reduce the weight while maintaining optimal compactness.

 By its thermal conduction properties, the. Composite phase change material is also very thermally conductive, which allows it to cool batteries whether it is in its freezing phase, in its thawing phase or in its maximum charge phase.

On the other hand, in the context of a local heating of the battery, also called "hot spot", the implementation of phase-change material makes it possible to increase the thermal inertia of the exchanger, thus limiting the sudden elevations. while evenly distributing the heat stored throughout its conductive surface, which reduces the risk of performance decline and / or damage to the batteries. Finally, in view of its latent heat of phase change, a composite phase-change material has a large thermal energy storage capacity in a "cold energy reserve" that can be used for the thermal regulation of the batteries during stopping phases of the compressor and / or the pump.

 The integration of such a composite change material within a heat exchanger thus makes it possible to reduce the energy consumption (and the CO2 emission), in the form of fuel and / or electricity, of the fuel circuit. thermal regulation of a motor vehicle, and thus to increase the electric autonomy of the vehicle

 According to a particular aspect of. In the invention, the composite phase change material has a latent heat of between 100 and 300 kJ per kg.

 Ced ensures a large storage capacity for thermal energy. According to a particular aspect of the invention, said first plate has a thickness of between 2 and 3 mm.

 The composite phase-change material can be shaped by molding which allows the heat exchanger to be easily dimmed so that it adapts to the space available under the batteries, and to respect the size of the battery pack. .

 Such a plate thus has optimum properties of flexibility and damping, and a small footprint,

 According to one embodiment of the invention, said composite phase-change material has a phase change temperature, or melting temperature, of between 9 and 13 ºC.

 Such a melting temperature is particularly suitable when the exchanger fulfills the refrigerant function that is to say when the heat exchanger is in a cooling phase of the batteries, as opposed to the operating phase during which the heat exchanger charges in calories without need da cooling battery.

According to another embodiment, said composite phase-change material has a phase change temperature, or melting temperature, of between 20 and 25 ºC. Such a melting temperature is particularly suitable when the heat exchanger performs the cooling function

 According to a particular aspect of the invention, said second plate is formed of a composite phase-change material.

 In a variant, the second pleque is aluminum.

 It should be noted that the mass of a composite phase change material is less than that of aluminum.

 According to a particular aspect of the invention, said second plate comprises heat transfer fluid inlet and outlet ports communicating with said circulation circuit.

 According to a particular aspect of the invention, said first plate and said second plate are sealed together by gluing.

 According to a particular aspect of the invention, said second material of the first plate consists of carbon fibers.

 The invention also relates to a device for thermal regulation of at least one electrical energy storage element comprising at least one heat exchanger as described above, said heat exchanger being arranged in thermal contact with at least one storage element. 'electric energy.

 According to a particular aspect of the invention, said heat exchanger takes the form of at least one electrical energy storage element.

 The composite phase change material may be shaped by molding or injection molding. This makes the exchanger more compact and adapts to the shape of the batteries.

 According to a particular aspect of the invention, said heat exchanger is in thermal contact with said electrical energy storage element, through at least one intercalary element.

 According to a particular aspect of the invention, the device "thermal-regulation comprises at least one holding spring of said heat exchanger against said at least one element for storing electrical energy.

Such a holding spring makes it possible to improve the heat exchange between the exchanger and the batteries. 4. Figuras

 Other characteristics and advantages of the invention will appear on reading the following description of particular embodiments, given as simple illustrative and non-limiting examples, and the appended figures, namely:

 Figure 1 - diagram of a device. thermal regulation of a battery, according to a non-limiting embodiment of the invention.

 Figure 2 - diagram of a heat exchanger according to a non-limiting embodiment of the invention, exploded and assembled, intended to be arranged in direct contact with a battery, through an Intercalaire element.

 The various elements illustrated by the figures are not necessarily represented on the real scale, the emphasis being more on the representation of the general operation of the invention.

5. Detailed Description of Particular Embodiments of the Invention

 Several particular embodiments of the invention are presented in the following description.

 It is understood that the present invention is not limited by these particular embodiments and that other embodiments can be implemented perfectly.

 The invention relates to a heat exchanger formed by superposition of two plates, of which at least one is composed of a composite phase change material (MPC).

 The use of such a heat exchanger is particularly advantageous for the thermal regulation of a motor vehicle battery since it allows, while satisfying the constraints of lightness, compactness, and ease of assembly, to limit the elevations sudden temperature rise in the battery, mitigate the formation of hot spots, and reduce the overall energy consumption of the thermal regulation circuit.

According to a first embodiment, and as illustrated in the diagrammatic view of FIG. 1, the invention relates to a heat exchanger 4 arranged within a pack * battery 1 for a motor vehicle. This battery pack 1 comprises walls delimiting a protective housing 2 in which at least one battery 3 is positioned.

 Conventionally, the battery 3 is composed of several cells / electrical energy storage cells or accumulators connected to each other,

 In order to regulate the temperature of this battery 3, the battery pack 1 is equipped

a heat exchanger 4 having a plurality of circulation ducts for a heat transfer fluid and positioned there under the battery 3.

 This heat transfer fluid may be of the refrigerant type, for example a mixture of water and gas, or a cooling liquid; for example a mixture of water and glycol.

 The coolant can thus absorb the heat emitted by the battery 3 in order to cool it or as needed, it can bring him heat if the temperature of the battery 3 is insufficient for its proper operation.

 As shown in FIG. 2, the circulation ducts are obtained by assembly (step A) by superposing two plates 41, 42.

 The two plates 41, 42 are assembled in a sealed manner by gluing, for example.

 . A first plate 41 has an array of parallel channels 5 whose ends are connected to collector channels.

 When this first plate 41 and a second plate 42, intended to be arranged close to and facing the battery 3; are fixed together, the portions of the second plate 42 vis-à-vis the channels 5 define with the latter a plurality of coolant circulation ducts and collector ducts.

 These heat transfer fluid circulation ducts are in fluid communication with two heat transfer fluid inlet and outlet ports 6 mounted on the second plate 42, via the collector ducts.

 The first plate 41 then provides a heat transfer fluid distribution function.

. According to the embodiments illustrated in FIGS. 1 and 2, the second plate 42 does not have a network of channels 5. However, according to alternative embodiments, the two plates 41, 42 or the second single plate 42 have such a network of channels 5, and therefore ensure the distribution of the coolant.

 According to a non-limiting embodiment, the two plates 41, 42 are manufactured by machining, three-dimensional printing, or molding, to meet the size of the battery pack and thus adapt to the available space under the batteries in the vehicle.

 According to a first embodiment, illustrated by FIG. 1, the heat exchanger 4 is arranged and kept in direct mechanical and thermal contact with the battery 3.

 This maintenance in direct contact is achieved by the implementation of an elastic element, for example a spring, which provides a thrust force for pressing the heat exchanger 4 against the battery 3.

 The heat exchanger 4 and the spring thus form a device for thermal regulation of the battery 3, and more generally of the battery pack 1.

 Once the heat exchanger 4 has been arranged against the battery 3, the heat exchanges between these two elements are carried out by conduction at the level of the second plate 42, one face of which is in contact with the battery 3.

 The coolant circulating in the ducts of the exchanger 4 can thus absorb the heat energy of the battery 3 through the second plate 42.

 According to a second embodiment, illustrated in FIG. 2, the heat exchanger 4 and the battery 3 are separated by an Intercalaire element 7, and are therefore in indirect contact (they are thus in thermal contact, but not mechanical). .

 The intermediate element 7, included in the thermal regulation device of the battery 3, is disposed between a face of the battery-3 and a face of the second plate 42.

 This intermediate element 7, for example of the "pad" type in slllcone, allows to improve the thermal contact, and the electrical insulation between the heat exchanger 4 and the battery 3 without altering the heat exchange by conduction between them, In the Illustrated example, the Intercalaire 7 element is open.

According to a first embodiment, the first plate 41 is formed of a composite phase-change material. Such a composite material consists of:

 at least one first thermal energy storage and retrieval material, which is a phase change material (PCM) able to store thermal energy and to restore this stored energy.

 at least one second material chosen to form a solid support matrix of the MCP, irrespective of the liquid or solid phase of the latter, the support matrix being constituted by carbon fibers whose This structure allows the first plate 41 to remain rigid regardless of the phase of the MCP and preventing leakage of the first phase change material into the liquid phase of the latter.

 Alternatively, as a second material, it is possible to provide a polymer with or without carbon fibers.

 The first material may in particular be an organic phase change material or vegetable inorganic or other origin. By way of example, the first phase change material consists of a mixture of paraffin and polymer which gives this material the ability to change physical state between a solid phase and a liquid phase within a restricted temperature range .

 Thus, in a particular example, the composite phase change material can be made in the form of a paraffin matrix, polymer and carbon fibers.

 According to alternative embodiments, the respective compositions of the MCP and the matrix differ from those described above without departing from the claimed protective field.

 According to this first embodiment, the thickness of this first plate 41 is between 2 and 3 mm, which makes it possible to obtain optimum properties of flexibility and damping, especially with regard to the deformations that this first plate 41 could be subjected to undergo, for example during assembly (A) of the heat exchanger 4.

 Still according to this first embodiment, the latent heat of phase change of the composite MCP is between 100 and 300 kl per kg.

The choice of this -value of values makes it possible to guarantee to the composite MCP a large capacity of storage of "cold" thermal energy that can be used for thermal regulation of the batteries during the stopping phases of the compressor and / or the pump.

 The integration of such a composite MCP within a heat exchanger therefore reduces the energy consumption, in the form of fuel and / or electricity, the thermal control circuit.

 According to this first embodiment, the control circuit has a refrigerant function.

 In this case, the phase change temperature of the MCP (for phase change material) is chosen between 9 and 13 ºC.

 In this temperature range, the thermal energy is stored or transferred by the composite MCP by simple change of state and height of the latent heat value of the MCP, without changing the latter temperature.

 The implementation of MCP therefore makes it possible to increase the thermal inertia of the heat exchanger 4 in this temperature range, thus limiting the sudden rise in temperature. temperature while evenly distribute the heat stored on the entire heat-conducting surface of the heat exchanger 4, which reduces the risk of performance decline and / or damage to the batteries.

 According to an alternative embodiment, the control circuit has a cooling function.

 In this case, the phase change temperature of the MCP is chosen between 20 and 25 ° C. As a result, the thermal inertia of the heat exchanger 4 is increased in this specific temperature range, thus limiting the risks of appearance of hot spots.

 According to the first embodiment, the first plate 41 is composite MCP / while the second plate 42 is aluminum.

 According to an alternative embodiment, these plates 41, 42 are both formed of composite MCP.

The composite MCP being three times lighter than aluminum, the substitution of aluminum by the. Composite MCP makes it possible to significantly lighten the heat exchanger 4, in addition to the effects related to the particularly advantageous thermal properties of the MCP, previously mentioned in the description. According to another embodiment, only the second plate 42 is composed of composite MCP, the first plate 41 being for example made of aluminum.

Claims

Heat exchanger (4) adapted for the thermal regulation of at least one electrical energy storage element (3), in particular for a motor vehicle, comprising an assembly by superposition of a first plate (41) and a second plate (42) defining a circulating circuit for a heat transfer fluid, said second plate (42) being intended to come into thermal contact with said at least one electrical energy storage element (3), said heat exchanger (4) being characterized in that said first plate (41) is formed of a composite phase change material comprising at least a first phase change material and at least a second material whose structure forms a matrix for supporting the first phase change material. 2. Heat exchanger (4) according to claim 1, characterized in that said composite phase change material has a latent heat of between 100 and 300 kJ per kg.  3. Heat exchanger (4) according to any one of claims 1 and 2, characterized in that said first plate (41) has a thickness of between 2 and 3 mm,  4. Heat exchanger (4) according to any one of claims 1 to 3, characterized in that said composite phase change material has a phase change temperature of between 9 and 13 ºC.  5. Heat exchanger (4) according to any one of claims 1 to 3, characterized in that said composite phase change material has a phase change temperature of between 20 and 25 ºC 6. Heat exchanger (4) according to any one of claims 1 to 5, characterized in that said second plate (42) is formed of a composite phase change material. 7. Heat exchanger (4) according to any one of claims 1 to 6, characterized in that said second plate (42) comprises heat transfer fluid inlet and outlet ports (6) communicating with said circulation circuit . 8. heat exchanger (4) according to any one of claims 1 to 7, characterized in that said first plate (41) and said second plate (42) are assembled sealingly by gluing,  9. Heat exchanger (4) according to any one of claims 1 to 8, characterized in that said second material of the first plate (41) is made of carbon fibers. 10. Device for thermal regulation of at least one electrical energy storage element (3), characterized in that it comprises at least one heat exchanger (4) according to any one of claims 1 to 9, said exchanger thermal device (4) being arranged in thermal contact with at least one electrical energy storage element (3).  11. Thermal control device according to claim 10, characterized in that said heat exchanger (4) matches the shape of said at least one electrical energy storage element (3). 12. Thermal control device according to claim 10, characterized in that said heat exchanger (4) is in thermal contact with said electric energy storage element (3), through at least one intermediate element (7). . 13. Thermal control device according to any one of claims 10 to 12, characterized in that it comprises at least one holding spring of said heat exchanger (4) against said at least one electrical energy storage element (3). ) ·