COOLING CIRCUIT AND METHOD ON A VEHICLE

Abstract

This relates to a cooling circuit comprising a liquid circulation path and arranged on the path: in series, an engine (2) and a radiator (8), mounted on a first branch in parallel between the inlet and outlet of the radiator, a store-exchanger (10) containing at least one volume: enclosing elements for storing and releasing thermal energy, involving a phase change material PCM, placed in a heat exchange relationship with said liquid (9), and around which are arranged at least one first layer containing a PCM and one second layer containing a porous thermally insulating material, and valves (14, 16, 18) so positioned as to direct the circulation of the liquid arriving from the engine toward the radiator and/or the store-exchanger.

Claims

1. A temperature management system on a vehicle cooling circuit using a heat transfer liquid, the circuit comprising a path for circulating the liquid and, arranged on the path: in series, a means for circulating the liquid along the path, an engine for moving the vehicle, whose components are to be placed in a heat exchange relationship with the liquid, and a heat exchanger having an inlet and an outlet for said liquid in order to place this liquid in a heat exchange relationship with another fluid within the exchanger, mounted on a first leg, between the inlet and the outlet of the heat exchanger, a heat store into which said liquid can enter and from which it can exit, and valves positioned so that liquid arriving from the engine flows toward the heat exchanger and/or the heat store, the heat store being a latent heat storage and thermal energy release unit containing at least one volume: enclosing elements made of phase change material (PCM) for storing and releasing the thermal energy contained in said liquid in view of a heat exchange with this liquid (9), and around which is installed a thermal barrier comprising at least one first layer containing a phase change material and which is surrounded by one second layer containing a porous thermally insulating material to thermally isolate said volume from the outside, characterized in that said thermal barrier has no physical contact with the heat transfer liquid circulating within the elements made of phase change material, where at least part of the thickness of a peripheral wall separates them, and at least some of said elements made of phase change material have a melting temperature that is lower than or equal to the melting temperature of the phase-change material of said first layer.

2. The system of claim 1, wherein the valves are positioned on the circuit in such a way that: in nominal mode, said liquid arriving from the engine can flow into the heat exchanger without flowing into the unit and then return to the engine, when the unit is in a state where calories are charged in said PCM elements, liquid arriving from the engine can at least partly flow into said unit (10) and into the heat exchanger and then return to the engine, and when the unit is in a state where calories are discharged through said PCM elements, liquid arriving from the engine can flow into the unit without flowing through the heat exchanger and then return to the engine.

3. The system according to claim 1, wherein the valves comprise the following: a first three-way valve so positioned as to circulate the liquid either toward the heat exchanger or toward said unit, a second two-way valve so positioned as to allow the liquid to circulate in the heat exchanger when it is open and prevent it from circulating therein when it is closed, and a third two-way valve so positioned as to: when the unit is in said calorie-charging state, circulate any liquid coming from the engine into the unit by closing any return to the engine thus bypassing the heat exchanger, and, when the unit is in said calorie-discharging state, circulate any liquid coming from the unit toward the engine.

4. The system according to claim 1, wherein: the valves comprise a first three-way valve and second, third and fourth two-way valves, with respect to the circulation of the liquid, the connection of the unit to the outlet of the heat exchanger is located downstream of a second leg of the circulation path, which: is connected to the first valve, which is so positioned as to share the flow of liquid coming out of the engine between the heat exchanger and said second leg, and opens downstream of the heat exchanger to allow for it to be bypassed when the first valve is closed toward the heat exchanger and open toward the second leg, with respect to the circulation of the liquid, the connection of the unit (10) toward the inlet of the heat exchanger is located upstream of the first valve and includes the second valve so positioned on the first leg as to: when it is in the open state, allow the liquid to circulate into the unit, when the first valve is in an open state, and, when it is in the closed state, prevent any liquid coming out of the unit from returning to the first valve, a third leg of the circulation path includes the third valve and is connected between the second valve and said unit on the first leg, and, when the third valve is in a closed state and the second valve is in an open state and when the unit is in a calorie-charging state, the first leg allows for the liquid coming out of the second valve to be circulated toward the unit, the third valve preventing, when it is in a closed state, any liquid from returning toward the engine through said third leg without flowing through the unit and, when it is in an open state, allowing liquid to return to the engine, when the fourth valve is closed, the fourth valve being so positioned as to: when it is in the open state, allow the liquid to return in this way after its passage through the unit, when said unit is in the calorie-charging state, and, when it is in the closed state, prevent the liquid coming from the third leg from returning to the heat exchanger.

5. The system according to claim 1, wherein the volume of said unit is provided with baffles used to make the liquid meander.

6. The system according to claim 1, wherein the unit contains, in the path of the liquid, a series of partitions that: split the volume into a succession of sub-volumes where said elements for storing and subsequently releasing the thermal energy are arranged in batches, and have at least one passage for communication between the sub-volumes.

7. The system according to claim 1, wherein at least the second layer containing the thermally insulating material is contained in at least one pocket impervious to said material and to air so that, an air gap corresponding to a pressure ranging from 10 to 104 Pa being established in said pocket, a vacuum insulation panel is formed.

8. The system according to claim 1, wherein said peripheral wall is made of a mouldable polymer material and laterally limits the volume or each volume; and the first and second layers are arranged in said peripheral wall.

9. The system according to claim 6, wherein: the unit comprises several structurally distinct adjacent modules that are stacked along an axis and each containing a sub-volume, and at least some of the modules individually comprise a bottom separating two adjacent modules transversely to said axis, each bottom corresponding to a said wall where said at least one communication passage allows the liquid to enter and exit, the passages being offset laterally with respect to each other along the axis.

10. The system according to claim 1, wherein: said at least one volume is delimited by the peripheral wall, said elements made of phase change material can be arranged in batches in said at least one volume, and the active thermal barrier is: either fully or partially integrated in the peripheral wall, or arranged around the peripheral wall.

11. A method for implementing the system of claim 1, in such a way that: in nominal mode, liquid having exited the engine flows through the heat exchanger, without said liquid flowing through the unit, and, when the unit is in a state where calories are charged through said elements made of phase change material, liquid having exited the engine flows through the heat exchanger and then returns to the engine.

12. The method of claim 16 wherein, after said calorie-charging state has been established in the circuit, a state is established in it in which calories are discharged from the unit's elements made of phase change material, by making all of the liquid having exited the engine flow through said unit, and then making said liquid return to the engine.

13. A method for implementing a system of claim 4, wherein: in nominal mode, liquid having exited the engine flows through the first valve and then through the heat exchanger, without flowing into the unit nor flowing through the second and third valves, which are then closed, the fourth valve being open, when the unit is in a calorie-charging state, liquid having exited the engine at least partly flows through the second valve, which directs it toward the unit, whereas passage through the first valve toward the heat exchanger and into the second leg is adjusted according to at least one physical parameter in the unit or in the heat exchanger, after which the liquid returns to the engine, the fourth valve being open and the third valve being closed, when the unit is in a calorie-discharging state, liquid having exited the engine flows through the first valve, which directs it exclusively toward the unit through the second leg, without flowing through the heat exchanger, the fourth valve being closed, after which the liquid returns to the engine, the second valve being closed and the third valve being open.

14. The method of claim 13, wherein: said physical parameter is a temperature and in nominal mode, the first valve shares the flow of said liquid between the heat exchanger and said second leg according to a temperature data item related to the heat exchanger.

15. The method of claim 14 wherein, if a power issue occurs on the heat exchanger in nominal mode due to a thermal overload detected by a temperature sensor, the fourth valve closes and the third valve opens, to ensure circulation of the liquid in the unit after passing through the heat exchanger, and then, once the temperature sensor detects the end of the thermal overload, the first valve again shares the flow of said liquid between the heat exchanger and said second leg, while said first valve had directed all of the liquid toward the heat exchanger, without going through the second leg, after the temperature sensor had detected the thermal overload.

16. A method for implementing a temperature management system on a vehicle cooling circuit using a thermal transfer liquid, the circuit comprising a path for circulating the thermal transfer liquid and, arranged on the path: in series, a means for circulating the thermal transfer liquid along the path, an engine for moving the vehicle, the engine having components that are to be placed in a thermal exchange relationship with the thermal transfer liquid, and a thermal exchanger having an inlet and an outlet for said thermal transfer liquid in order to place the thermal transfer liquid in a thermal exchange relationship with another fluid within the thermal exchanger, mounted on a first branch, between the inlet and the outlet of the thermal exchanger, a thermal store into which said thermal transfer liquid can enter and from which it can exit, the thermal store containing at least one volume: enclosing elements including phase change material (PCM) for storing and releasing thermal energy contained in said thermal transfer liquid in view of a thermal exchange with the thermal transfer liquid, and around which is installed a thermal barrier comprising a layer containing a porous thermally insulating material to thermally isolate said volume from the outside, and valves positioned so that the thermal transfer liquid arriving from the engine flows toward the thermal exchanger and/or the thermal store, in such a way that: in nominal mode, the thermal transfer liquid having exited the engine flows through the thermal exchanger, without said thermal transfer liquid flowing through the unit, and when the unit is in a state where calories are charged through said elements including phase change material, thermal transfer liquid having exited the engine flows through the heat exchanger and then returns to the engine.

Description

[0084] If necessary, the various aspects of the invention will be better understood and other characteristics, details and advantages thereof will become apparent upon reading the following description, given by way of non-limiting example and with reference to the annexed drawings (in which possible auxiliaries required for the proper circulation of the fluids are not shown: non-return valves, filters, etc.) and in which:

[0085] FIGS. 1 to 3, on the one hand, and 4 to 8, on the other hand, show two examples of cooling circuits incorporating a store/exchanger, respectively in series and in parallel,

[0086] FIGS. 9, 10 schematically show two versions of a store/exchanger, (FIG. 1), with details concerning the element(s) that it consists of,

[0087] FIG. 11 schematically shows a store/exchanger module laterally surrounded by an active thermal barrier hereafter identified by 15/23, within at least one airtight enclosure;

[0088] and FIG. 12 schematically shows a vertical section of three store/exchanger modules, lying upon another and incorporating an active thermal barrier in their side wall, each module being moulded.

[0089] FIGS. 1 to 8 thus illustrate two possible modes of operation Integration of a thermal energy store in a vehicle cooling loop. Two types of integration are therefore possible:

1. Serial Integration; FIG. 1 to 3:

[0090] The planned cooling circuit 1 on the vehicle fitted the heat engine 2, for its engine-driven movement, and wherein circulates water in this case, comprising a closed-circuit circulation path 4.

[0091] Within it, a means 6 for circulating the liquid, such as a pump, the engine 2, whose engine block is to be cooled by the water circuit, and the radiator 8 (generally an air-liquid exchanger, if not a liquid-liquid exchanger, such as a water-water exchanger) are arranged in series on the basic closed circuit 4a.

[0092] While the engine 2 shown in the example is a heat engine, it could also be an electric motor. Therefore, the present solutions are applicable on vehicles with heat engines for movement, on electric vehicles and on hybrid vehicles (with heat engines and electric motors for movement).

[0093] In the example shown, the unit 10 for storing and subsequently releasing the previously stored thermal energy is mounted in parallel on a first branch 12 between the inlet 8a and the outlet 8b of the radiator, in the direction in which it will allow for the radiator 8 to be bypassed in discharge mode), it being specified that this arrangement does not imply an operation that must be parallel (see the charge mode below).

[0094] Valves 14 (three-way) and 16,18 (two-way) are so positioned as to direct the flow of the liquid arriving from the engine toward the radiator and/or the unit 10. Typically, these will be solenoid valves automatically controlled by software of a remote computer 28. The valves 14, 16 can be on-off valves, the one 14 with variable opening/closing, must be progressive.

[0095] In a standard manner, the water coming out of the engine is hot (typically between 70 and 95 C.) and the radiator 9 is used to cool it (between 60 and 75 C.). It will therefore be possible to use this hot water as a heat transfer fluid to store (charge) and then release (discharge) part of the thermal energy it contains via the unit 10.

[0096] To this end, FIG. 9 to 11 show possible embodiments that may be suitable to ensure the dual function above, these embodiments may also be applied to the parallel assembly shown in FIG. 4 to 8.

[0097] In this particular case, the unit 10 contains at least one (here several) volume 7.

[0098] Each volume contains elements 13 for storing and releasing energy including phase change material (PCM), placed in a heat exchange relationship with the circulating liquid.

[0099] In order to promote latent heat storage (charge mode below) via these elements 13, at least some of them (if they include solid-liquid PCM) will favourably have a melting point that is less than or equal to the melting temperature of the PCM(s) of said first layer 15 (this also applies to case 2 below).

[0100] At least one first layer 15 containing a PCM and one second layer 23 containing a porous thermally insulating material are installed around each volume.

[0101] At the outlet of the engine block 2, the water circulating in it can be led directly to the cooling element (radiator 8). It can also be entirely (100%) or partially deviated to the unit's 10 storage volume(s), to ensure its energy charge.

[0102] In NOMINAL mode, as shown in FIG. 1: 0% of the liquid circulating in the circuit 4 flows through the unit 10. However, 100% of this fluid feeds the radiator 8. Valve 18 is closed. Valve 16 is open.

[0103] When the unit 10 is in CHARGE mode, as shown in FIG. 2: 0% of the liquid circulates via the radiator 8, whereas 100% of this fluid feeds the unit 10. Valve 18 is closed. Valve 16 is open.

[0104] When the unit 10 is in DISCHARGE mode, as shown in FIG. 3: 0% of the liquid circulates via the radiator 8, whereas 100% of this fluid feeds the unit 10. Valve 18 is open. Valve 16 is closed.

[0105] Therefore, on the circuit 4: [0106] the first three-way valve 14 is so positioned that the liquid arriving from the engine circulates toward the heat exchanger 8 and/or the unit 10, [0107] and the second two-way valve 16 is so positioned as to allow the liquid to circulate in the radiator when it is open and prevent it from circulating therein when it is closed, [0108] whereas the third two-way valve 18 is so positioned as to achieve the following: [0109] when the unit 10 is in said calorie-charging state (FIG. 2), circulate the liquid coming from the engine 2 into the unit 10 by closing the return 10a from the branch 10 to the engine thus bypassing the radiator, [0110] and, when the unit 10 is in said calorie-discharging state (FIG. 3), circulate the liquid coming out of the unit 10 toward the engine 2.

[0111] Using the assembly introduced above, the detailed operation is as follows, as illustrated:

[0112] In nominal mode and at the outlet of the engine 2, the liquid flows through the first valve 14 and then entirely into the radiator 8, without flowing into the unit 10. The second valve 16 is open and the third valve 18 is closed.

[0113] When the unit 10 is in a calorie-charging state, and at the outlet of the engine, the liquid flows through the first valve 14, which directs it exclusively into the unit 10, after which the liquid flows into the radiator 8 and then returns to the engine. The second valve 16 is open and the third valve 18 is closed.

[0114] When the unit is in a calorie-discharging state, the liquid flows through the first valve 14 and then entirely into the unit 10 and then returns to the engine 2. The second valve 14 is closed and the third valve 18 is open.

2. Other Integration (Called Parallel); FIG. 4 to 8:

[0115] In this case, the valves comprise a first three-way valve 14 and second 16, third 18 and fourth 20 two-way valves.

[0116] Said first branch 12, which includes the unit 10, also includes the second valve 16.

[0117] With respect to the circulation of the liquid, the connection of the unit 10 to the outlet 8b of the radiator is located downstream of a second branch 22 of the circulation path, which: [0118] is connected to the first valve 14, which is so positioned as to share the flow of liquid coming out of the engine 2 between the radiator 8 and said second branch 22, [0119] and opens downstream of the radiator 8 to allow for it to be bypassed when the first valve 14 is closed toward the radiator and open toward the second branch.

[0120] On the basic closed circuit 4a, the first branch 12 thus is connected between a point upstream of the first valve 14 and a point downstream of the connection of the second branch 22, between the outlet of the radiator 8 and the fourth valve 20.

[0121] Furthermore, with respect to the circulation of the liquid, the connection of the unit 10 to the inlet of the radiator is located upstream of the first valve 14 (between it and the outlet of the engine 2) and includes the second valve 16, which is so positioned as to: [0122] when it is in the open state, allow the liquid to circulate into the unit 10, when the first valve 14 is in an open state, [0123] and, when it is in the closed state, prevent any liquid coming out of the unit from returning to the first valve.

[0124] A third branch 24 of the circulation path includes the third valve 18 and, on the first branch 10, is connected between the second valve 16 and the unit 10 and a point downstream of the third valve, on the basic circuit 4a.

[0125] Thus, when the third valve 18 is in a closed state and the second valve 16 is an open state and when the unit 10 is in a calorie-charging state, the third branch 24 allows the liquid coming out of the second valve to circulate toward said unit.

[0126] And, when it is in a closed state, the third valve 18 prevents liquid from directly returning to the engine 2 without flowing through the unit 10 and, when it is in an open state, it allows the liquid to directly return in this way, when the fourth valve 20 is closed.

[0127] The assembly of this fourth valve 20 on the basic closed circuit 4a between the downstream connection of the first branch 12 and the engine 2, in fact allows it to achieve the following: [0128] when it is in the open state, allow the liquid to return to the engine, after its passage through the unit 10, when said unit is in the calorie-charging state, [0129] and, when it is in the closed state, prevent the liquid from returning to the radiator 8, the unit 1 or the second branch 22.

[0130] With such an assembly, at the outlet of the engine block, the water can be made to circulate both into the unit 10 or into the radiator 8. The unit 10 can be fed with the fluid flowing toward the radiator or with the fluid returning from the radiator.

[0131] In NOMINAL mode: 0% of the fluid flows through the unit 10; the valves 16, 18 are closed, whereas, through the first valve, which is open, up to 100% can flow through the radiator 8, from the engine's 2 outlet. The adjustment of the flow rate in the radiator, via the valve 14, depends on the thermal load produced by the engine 2 and thus on the opening of this valve 14.

[0132] When the unit 10 is in CHARGE mode: the setting of the first valve 14 can be adjusted according to the unit's 10 and the radiator's outlet temperature.

[0133] When the unit 10 is in DISCHARGE mode: 0% of the fluid circulates through the radiator, while 100% of the fluid coming from the engine 2, and therefore needing to be cooled, circulates through the bypass (bypass branch) 22 of the radiator. The third valve 18 is open. The second and fourth valves are closed. Controlling these three valves leads to 100% circulating through the unit 10.

[0134] Thus, in NOMINAL mode and at the engine's outlet, the liquid will flow through the first valve 14 and then into the radiator, without flowing through the unit 10, the fourth valve 20 being open and the second and third valves 16, 18 being closed.

[0135] When the unit is in a calorie-charging state and at the engine's outlet, the liquid will at least in part flow through the second valve 16, which will direct it toward the unit 10, whereas passage through the first valve 14 toward the radiator and into the second branch 22 will be adjusted according to at least one physical parameter in the unit or in the radiator, after which the liquid will return to the engine, the fourth valve 20 being open and the third valve 16 being closed.

[0136] Lastly, when the unit 10 is discharging calories, the liquid will flow through the first valve 14, which will direct it exclusively into the unit through the second branch 22, without flowing through the radiator, the fourth valve 20 being closed. Subsequently, the liquid will return to the engine 2, the second valve 16 being closed and the third valve 18 being open.

[0137] As the physical parameter used to adjust the passage through the first valve 14 in the charging state, we recommend choosing a temperature, preferably the radiator outlet temperature, which can be read by a sensor 26 connected to the computer 28.

[0138] Thus, particularly in nominal mode, the first valve 14 will share the flow of liquid coming out of the engine 2 between the radiator and the second branch 22 according to the temperature data related to the radiator.

[0139] Moreover, as mentioned above, the assembly according to this parallel integration shown in FIGS. 4 to 8 will make it possible to handle, in nominal mode, the situation where a power issue will occur on the radiator 8, following a thermal overload detected by a temperature sensor, such as sensor 26 (e.g. a temperature above 75 C.).

[0140] In this case, the fourth valve 20 will close and the third valve 18 will open, to then ensure that the liquid circulates into the unit 10 after flowing through the radiator 8 (see FIG. 7).

[0141] 100% of the flow rate may again be made to circulate into the unit, wherein one could then provide dedicated PCM elements 13 (thus complementary to those mentioned above having a lower melting temperature) having a higher melting temperature than that of the PCM(s) of the layer 15, for example a melting temperature of 90 C. rather than the 70/75 C. of the other elements in the layer 15, thus allowing for a temperature peak to be cancelled out.

[0142] Then, once the temperature sensor has detected the end of the thermal overload (e.g. a temperature of less than 70 C.), the first valve 14 will again share the flow of liquid coming out of the engine between the radiator 8 and said second branch 22, while it had directed the liquid exclusively to the radiator 8, thus without flowing through the second branch, after the thermal overload had been detected by the temperature sensor 26 (see FIG. 8). The nominal mode can then be restored.

[0143] Regarding the structure of the unit 10, reference may be made to the preferred examples in FIGS. 9 to 11.

[0144] The diagram of FIG. 9 shows a thermal device or unit 10 into which and out of which flows a fluid 9 (heat transfer fluid in the application for the cooling circuit), its circulation being handled by circulation means 6, such as a pump.

[0145] The heat store-exchanger 10 installed in the circuit 4 therefore is a unit that will store thermal energy through phase change(s) of at least one PCM, and then subsequently release at least part of this energy by additional phase change(s) (of at least some) of this(these) PCM(s).

[0146] The unit 10 thus includes one or several modules 3 each enclosing an internal volume 7 in which the fluid 9 circulates and in which PCM elements 13 for storing and releasing thermal energy are placed in contact with the fluid to enable heat exchanges.

[0147] As shown in FIG. 10, the (each) interior volume 7 will be favourably provided with baffles. In order to define them, a series of walls 29 may be provided along the fluid path: [0148] splitting the volume 7 into a succession of sub-volumes, such as 7a, 7b, 7c, etc. in which the elements 13 will be arranged in batches around and/or in which the fluid will circulate in heat exchange relationships, [0149] and having at least one communication passage 30 between the sub-volumes.

[0150] Each module can be opened at 31 and closed through a bottom 290.

[0151] In the direction 27 in which the modules 3 are lying upon another, on either side of the stack that they form, a cover 32 will then close each opening 31 and may be doubled up with a pocket 34 in the form of a VIP. A mechanical protection plate 36 may close the whole, along the axis 27, as shown. In this location, fastening means 40, which may be tie rods, mechanically fasten the modules together along the axis 27.

[0152] For purposes of readability, FIGS. 10, 11 do not show the elements 13. These can be seen in FIG. 9. They can be spheres or ovoids.

[0153] FIG. 10 makes it clear that the baffles 12 can be formed by the fact that the walls 29 are in this case bottoms of bodies or modules 3, which are arranged in line (direction 27), one after the other, communicating two by two through a passage 30 formed in each bottom 29.

[0154] Each module 3 consists of a lateral peripheral wall 5 that completes the pierced bottom 290. Each transverse wall 290 and its through-passage 30 thus form a retarder to the free flow of fluid between its inlet 33 and its outlet 35. Preferably, two passages 30 of successive modules will be offset laterally, with respect to the axis 27 as shown schematically. Opposite the bottom, each module is open, at 31, in such a way that, when coming out of a passage 30, the fluid directly arrives in the internal volume of the adjacent module. The circulation between sub-volumes within the unit can be in series or in parallel.

[0155] In addition, a housing 96 (in this case closed on all sides) is arranged around the modules, which provides mechanical protection and gathers the modules together. The unit 10 may only include a single module 3. Each module shown in FIG. 9 can be the one shown in FIG. 10 or 11, which includes the additional elements 13.

[0156] In a module of the solution shown in FIG. 10, the baffles 12 are (essentially) created by the internal walls 29 which, within the space 7 delimited by the peripheral wall 5 and the pierced bottom 290, split this space into sub-volumes 7a, . . . 7c. Each wall 29 being interrupted at one of its lateral ends before reaching the wall 5, this is where one of the passages 30 is defined which, in connection with the wall in question and preferably an alternation at the lateral end thus opened, forms a baffle. The arrows in FIG. 10 show the meandering fluid.

[0157] In each case, a rubber compound as described in EP2690137 or in EP2690141 may be provided as a structure of elements 13, i.e. in the second case a cross-linked compound based on at least one room temperature vulcanized (RTV) silicone elastomer and comprising at least one phase change material (PCM), said at least one silicone elastomer having a viscosity measured at 25 C. according to standard ISO 3219 that is less than or equal to 5000 mPa.Math.s. The thermal phase change material (PCM) may consist of n-hexadecane, eicosane or a lithium salt, all having melting points below 40 C. Alternatively, the PCM could be based e.g. on fatty acid, paraffin, or eutectic or hydrated salt, or even fatty alcohols.

[0158] Around the/each volume 7, an active thermal barrier (15/23) provides a thermal insulation with respect to the outside and at least one retarding function in the transmission of thermal energy between the inside and outside of the unit.

[0159] This active thermal barrier must be either of the following: [0160] integrated in whole or in part to the lateral peripheral wall 5 (as shown in FIG. 12, for the two layers 15/23 embedded in the wall, or in FIG. 11 where the layer 15 is arranged in slots in the wall), [0161] arranged around the wall 5 (FIGS. 9, 10 and also 11 for the layer 23).

[0162] The barrier must therefore comprise at least one first layer 15 containing a PCM and one second layer 23 containing a thermally insulating material. In principle, the second layer 23 must be arranged around the first layer 15.

[0163] The thermal barrier is sensitive to heat exchanges in the overall volume 7, but has no physical contact with the liquid 9 (which circulates within the PCM elements 13). They are separated at least by part of the thickness of the peripheral wall 5.

[0164] In order to optimize the thermal efficiency of the active barrier, we recommend that it includes at least one VIP forming a pocket 19 under vacuum wherein at least the second layer 23, which preferably will coexist with the PCM layer 15 within the same airtight enclosure.

[0165] The sheet(s) or film(s) forming each pocket may typically be embodied as a multilayer film comprising polymer films (PE and PET) and aluminum in the form of, for example, laminated (sheet of thickness in the order of ten micrometre) or metallized (vacuum deposition of a film of a few tens of nanometres).

[0166] The material of the layer 23 will favourably consist of a porous material (if an air gap is to be achieved), such as a silica powder or an aerogel, confined in a deformable or conformable sheet that is impervious to water vapour and gases. The VIP obtained will be emptied of the air it contains to obtain a pressure of e.g. a few millibars and can then be sealed. Typically, the thermal conductivity of such a VIP will be 0.004/0.008 W/m.K. Examples of VIPs and of super-insulating material that may apply here are provided in PCT/FR2014/050267 and WO2014060906 (porous material), respectively.

[0167] The solutions presented above will favourably enable, in a volume and weight acceptable among others by aircraft or automotive manufacturers, quick storage of the available thermal energy after about 6 to 10 minutes, retention of this energy for 12 to 15 hours, before its quick release, typically within a few minutes (in particular less than 2 or 3).