The invention concerns a heat exchange device and a method and a system including this kind of device for thermal management of a battery. It is intended to be used in motor vehicles.

There are known air conditioning systems for motor vehicles including a loop for circulation of a coolant fluid. They include in series along the loop a compressor, a condenser, an expansion valve and an evaporator. They are generally rated to produce 6 to 8 kW of cooling power for cooling the passenger compartment of the vehicle.

In parallel with this, with the development of hybrid or entirely electric drive motor vehicles, it is also necessary to have systems for cooling the batteries used to supply energy to the motors. It has therefore already been proposed to make use of the air conditioning loop by providing it with a heat exchanger, in parallel with the evaporator, to cool a heat-exchange fluid that in turn cools the battery.

However, it is estimated that modern battery cooling requirements correspond to an additional power of between 1 and 4 kW to be provided by the loop for circulation of the coolant fluid. The main limitation then stems from the cubic capacity of the compressor and the performance of the condenser, which has to evacuate between 8 and 14 kW of thermal power at the level of the front face of the vehicles.

It is moreover anticipated by the applicant that the coolant power requirement is going to increase in the near future if it is wished to be able to propose electric vehicles compatible with rapid charging of the battery, that is to say charging in less than 15 minutes. The power to be dissipated at the front face of the vehicle will therefore be between 15 and 25 kW inclusive.

It will also be necessary to be able to circulate the coolant fluid at a flow rate enabling evacuation of this kind of power. The corresponding flow rates as estimated by the applicant would consequently increase from the order of 200 kg/h at present to approximately 400 kg/h for this new type of system.

The currently known condensers are little if at all compatible with such requirements. A first solution would be to upgrade them. However, this solution is not compatible in all cases with the area available on vehicle front panels. Moreover, they would generate significantly increased head losses, which would simultaneously compromise their heat exchange performance .

The present invention aims to alleviate at least in part the aforementioned problems and to this end proposes a heat exchange device comprising at least two heat exchangers, configured to be installed on the front face of a motor vehicle, said exchangers having a surface for heat exchange between a coolant fluid intended to flow through said exchangers and a flow of air intended to pass through said exchangers, at least a part of said exchange surface, termed the condensation part, being configured to allow condensation of said coolant fluid, said device being configured so that said coolant fluid passes through said exchangers or at least said condensation part of said exchangers in parallel.

By dividing the exchange area into at least two distinct exchangers, the invention offers the advantage of calling on exchangers having dimensions more easily compatible with the locations available on the front panel of the vehicle, or even exchangers having standard or near standard dimensions. Moreover, by placing the exchangers in parallel in the flow of coolant fluid, the flow rate of fluid is divided in each of them, which limits head losses and simultaneously improves their performance in terms of heat exchange.

According to various supplementary features of the invention, separately or in combination:

- said exchangers are disposed alongside one another so as to be situated in parallel in the flow of air,

- said exchangers are disposed one by the other so as to be situated symmetrically with respect to a longitudinal axis of the vehicle,

- said exchangers are two in number,

- alternatively, said exchangers are at least three in number, namely one or more central exchangers and at least two lateral exchangers disposed on respective opposite sides of the central exchanger or exchangers,

- said central exchanger or exchangers have, taken together, an exchange surface larger than an exchange surface of at least one of the lateral exchangers,

- said lateral exchangers are disposed in a plane different from a plane in which the central exchanger or exchangers is or are disposed,

- at least one of said exchangers includes a bottle,

- the bundle of said exchanger or exchangers provided with a bottle further includes a subcooling area,

- said bottle configured to have said coolant fluid pass through it between said condensation part and said subcooling area,

- each of said exchangers includes one of said bottles, which may be a drier bottle,

- the bundle of each of the exchangers includes one of said subcooling areas,

- said device is configured so that said coolant fluid passes through all of said exchangers in parallel,

- alternatively, only one of said exchangers, termed the main exchanger, is provided with one of said bottles ,

- only the bundle of the main exchanger is provided with one of said subcooling areas,

- the condensation part of said other exchanger or exchangers is connected to the bottle of the main exchanger so that, on leaving the condensation part of said other exchanger or exchangers, the coolant fluid passes into the bottle of the main exchanger,

-the condensation part of said other exchanger or exchangers is connected to the bottle of the main exchanger so that, on leaving the condensation part of said other exchanger or exchangers, the coolant fluid passes into the bottle of the main exchanger,

-the main exchanger is the central exchanger.

The invention also concerns a system for thermal management of a battery including a loop for circulation of a coolant liquid, said loop including a heat exchange device as described hereinabove.

According to various supplementary features of the invention, separately or in combination:

- said system is configured to function in a first mode in which said coolant fluid circulates in only one or only some of said exchangers, notably in the main exchanger, and in a second mode in which the coolant fluid circulates in all said exchangers, in particular in the case of fast charging of the battery,

- said system includes a supplementary heat exchanger, enabling exchange of heat between the coolant fluid and a fluid intended for thermal management of the battery,

- said system includes a loop for circulation of the fluid intended for thermal management of the battery, said supplementary heat exchanger being situated in the loop for circulation of the coolant liquid and in the loop for circulation of the fluid intended for thermal management of the battery.

The invention further concerns a method for thermal management of a battery utilizing a thermal management system as described above, in particular in the context of fast charging the battery.

Other features, details and advantages of the invention will emerge more clearly on reading the description given hereinafter by way of illustration and with reference to the drawings, in which:

- figure 1 is a partial diagrammatic illustration of a system for thermal management of a battery in accordance with a first variant embodiment of the invention,

- figure 2 is a partial diagrammatic illustration of a thermal management system in accordance with a second variant embodiment of the invention, - figure 3 is a partial diagrammatic illustration of a thermal management system in accordance with a third variant embodiment of the invention,

- figure 4 is a diagrammatic illustration of a loop for circulation of a fluid intended for thermal management of the battery, designed to complete the thermal management system shown in figures 1 to 3,

- figure 5 is a diagrammatic illustration of a first embodiment of a heat exchange device according to the invention, intended to equip the thermal management system from figure 3,

- figure 6 is a diagrammatic illustration of a second embodiment of a heat exchange device according to the invention, intended to equip the thermal management system from figure 3.

In the various figures, identical elements are identified by the same references.

As shown in figures 1 to 4, the invention concerns a system for thermal management of a battery 1, including a closed loop 2 for circulation of a coolant liquid. The coolant fluid may for example be a supercritical fluid such as R-744 carbon dioxide. The coolant fluid is again for example a subcritical fluid such as R-134a fluorinated coolant fluid or 1234yf non-fluorinated coolant fluid.

Said loop 2 for circulation of the coolant fluid includes a heat exchange device 3. Said heat exchange device includes at least two heat exchangers 4, configured to be installed on the front face of a motor vehicle. This will be expanded on later.

Here said system further includes a closed loop 5 for circulation of a fluid intended for thermal management of the battery 1. Said fluid is, for example, a heat- exchange liquid, notably a mixture of water and an antifreeze liquid such as glycol.

Said system could further include a supplementary heat exchanger 6, situated in the loop 2 for circulation of the coolant liquid and in the loop 5 for circulation of the fluid intended for thermal management of the battery in order to allow exchange of heat between these two fluids.

Said loop 2 for circulation of the coolant fluid includes a compressor 10 and, downstream of the latter in the direction of flow of the coolant fluid, the exchanger or exchangers 4 of the heat exchange device 3. Farther downstream, the loop 2 includes a first branch 12 and a second branch 14 in parallel with each other between the heat exchange device 3 and the compressor 10.

Here the first branch 12 includes a first valve 16 for opening/closing the circulation of the coolant fluid in said first branch 12, a first expansion valve (TXV) 18 and an evaporator 20. The evaporator 20 is configured to allow exchange of heat between the coolant fluid and a flow of air intended to cool the passenger compartment of the vehicle with a view to its air conditioning. The first branch 12 is configured to allow circulation of the fluid from upstream to downstream through the first valve 16, an expansion part of the first expansion valve 18, the evaporator 20 and then a control part of the first expansion valve 18, before passing into the compressor 10.

Here the second branch 14 includes a second valve 22 for opening/closing the circulation of the coolant fluid in said second branch 14, a second expansion valve 24 and the supplementary heat exchanger 6. Said supplementary exchanger is, for example, a chiller. The second branch 14 is configured to allow upstream to downstream circulation of the fluid through the second valve 22, an expansion part of the second expansion valve 24, the chiller 6 and then a control part of the second expansion valve 24, before passing into the compressor 10.

The loop 5 for circulation of the fluid intended for thermal management of the battery includes, in the direction of circulation of said fluid, a pump 26 for circulation of said fluid, possibly a device 28 for heating said fluid, and a device 30 for thermal management of the battery 1 and said chiller 6. The device for thermal management of the battery 1 includes, for example, tubes provided with channels for circulation of the liquid for thermal management of the battery 1, said tubes being in direct or indirect thermal contact with the battery 1.

If cooling of the battery 1 is required, the heating device 28 is inactive. For its part, the chiller 6 has the fluid intended for thermal management of the battery and the coolant fluid pass through it, said two-phase coolant fluid changing to the vapour phase in said chiller 6, so that the fluid intended for thermal management of the battery is chilled.

If heating of the battery 1 is required, the heating device 28 is active. For its part, the chiller 6 continues to have the fluid intended for thermal management of the battery 1 pass through it but does not have much or any of the coolant fluid pass through it, with the result that the fluid intended for thermal management of the battery is not chilled much or at all .

The aim of this thermal management of the battery is for it to function in a temperature range enabling its good performance to be assured, notably between 20 and 40 ⁰ C .

Said loop 5 for circulation of the fluid intended for thermal management of the battery could comprise one or more branches 29, shown in part, notably connected to other heat exchangers, in particular vehicle front face exchangers, not shown. Said branch or branches 29 is or are situated, for example, in the direction of circulation of the fluid intended for thermal management of the battery, in parallel with the chiller 6, between the pump 26 and the device 30 for thermal management of the battery 1.

A single loop 5 for circulation of the fluid intended for thermal management of the battery is shown here as being able to form part of each of the embodiments of the thermal management system shown in figures 1 to 3. It will of course be possible to modify the loops 5 for circulation of the fluid intended for thermal management of the vehicle, notably as a function of the embodiments of the loops 2 for circulation of the coolant fluid, in particular of their heat exchange device 3. Said coolant fluid passes through the exchangers 4 of the heat exchange device 3. To be more precise, the exchangers 4 of the heat exchange device 2 have a surface 32 for heat exchange between the coolant fluid and a flow F of air intended to pass through the exchangers 4 of said heat exchange device 3. At least a part of said exchange surface 32, termed the condensation part, is configured to allow condensation of said coolant fluid. The heat exchangers 4 of said heat exchange device 3 therefore enable dissipation into the air of the heat generated by cooling the battery 1, via the chiller 6, and/or the air conditioning system of the vehicle, via the evaporator 20. As mentioned above, in particular in the case of requiring rapid cooling of the battery, the power to be dissipated can be up to 15 to 25 kW. Moreover, the coolant fluid flow rate can exceed 400 kg/h.

By way of example, the exchange area 32 includes tubes for circulation of the coolant fluid discharging into the manifolds of the exchanger. Spacers are preferably disposed between the tubes to increase the exchange area .

According to the invention, said heat exchange device 3 is configured so that said coolant fluid passes through the exchangers 4 of said device in parallel. This is the case in particular in the embodiment of figures 1 and 2.

Alternatively, in the embodiment from figures 3 and 5 and 6, said heat exchange device 3 is configured so that said coolant fluid passes through said condensation part 34 of the exchangers 4 of said device 3 in parallel.

In other words, in the configuration of the various embodiments of the thermal management system from figures 1 to 3, the condensation part 34, or even the entirety of the exchangers 4 of the heat exchange device 3, are mounted in shunt, in other words in parallel, between the compressor 10, on the one hand, and the first and second branches 12, 14 of the coolant fluid circuit, on the other hand, depending on the circulation of said coolant fluid.

Thanks to the invention, the coolant fluid flow rate is therefore divided in each of the heat exchangers 4 of the heat exchanger device 3, which limits head losses. Moreover, this could favour good heat exchange performance by enabling preservation of the greatest possible pinch effect between the ambient temperature and the saturation temperature of the coolant fluid. Moreover, by dividing the necessary exchange surface between a plurality of exchangers, it is possible to use exchangers having a standard or close to standard exchange surface, that is to say one with an area between 20 and 30 dm ² for the larger of them. In any event this avoids having to use heat exchangers the size of which would render their integration into the front face of the vehicle difficult or even impossible.

The heat exchangers 4 of the heat exchange device 3 are preferably disposed alongside one another to be situated in parallel in the flow of air. However, a disposition with one behind the other in series in the flow of air is equally possible.

Said heat exchange device 3 could include a supporting framework, not shown, common to said exchangers 4. Alternatively, the heat exchangers 4 of the heat exchange device 3 could be mounted independently on the vehicle .

Said heat exchangers 4 of the heat exchange device 3 are advantageously disposed one by the other so as to be symmetrically situated relative to a longitudinal axis of the vehicle.

In the embodiment from figure 1, they are two in number. Alternatively, the exchangers 4 of the heat exchange device 3 are at least three in number, namely one or more central exchangers and at least two lateral exchangers, disposed on respective opposite sides of the central exchanger or exchangers.

As is the case in the embodiment from figures 2 and 3, they are preferably three in number, namely a central exchanger 4c and two lateral exchangers 41, disposed on respective opposite sides of the central exchanger 4c. The central exchanger 4c is configured to be situated, for example, behind the grille of the vehicle and/or the lateral exchangers 41 are configured to be situated, for example, at the front of the wheel arches of the vehicle.

The central exchanger 4c advantageously has a larger exchange surface than the at least one, or even each, of the lateral exchangers 41. By way of example, the central exchanger 4c has an exchange surface with an area of 20 to 25 dm ² and each of the lateral exchangers has an exchange surface with an area of the order of 5 to 15 dm ² , notably 10 dm ² .

In figure 1 the exchangers 4 of the heat exchange device 3 are disposed in substantially the same plane.

Alternatively, in figures 2 and 3, said lateral exchangers 4c are disposed in a plane different from the plane in which the central exchanger 4c is disposed. This kind of disposition is in particular suitable for positioning the lateral exchangers 41 in the wheel arches, as previously mentioned.

According to the various embodiments shown, at least one of said exchangers 4 of the heat exchange device 3 includes a bottle 36 and the bundle 32 of said exchanger or exchangers 4 provided with a bottle 36 further includes a subcooling area 38 (visible only in figures 5 and 6) . Said bottle 36 is configured to have said coolant fluid pass through it between said condensation part 34 and said subcooling area 38.

In an exchanger of this kind, the bottle 36 serves to enable separation of phase between the coolant fluid in the liquid phase and any bubbles of coolant fluid in the vapour phase at the outlet of the condensation part 34. As a result, the coolant fluid entering the subcooling area is entirely in the liquid phase and can undergo a reduction of temperature. The bottle 36 can also be provided with a filter and/or a desiccant material . In the embodiment from figures 1 and 2, each of said exchangers 4 of the heat exchange device 3 includes one of said bottles 36 and the bundle 32 of each of the exchangers 4 includes one of said subcooling areas. Moreover, said heat exchange device 3 is configured so that all said exchangers 4 have said coolant fluid pass through them in parallel, in the entirety of each of said exchangers 4.

According to the embodiment from figures 3 and 5 and 6, only one of said exchangers, termed the main exchanger 4c, is provided with one of said bottles 36 and only the bundle 32 of the main exchanger 4c is provided with one of said subcooling areas 38. In other words, the other exchangers 41 of the heat exchange device 3 have neither bottle nor subcooling area. Moreover, the condensation part 34 of said other exchanger or exchangers 41 is connected to the bottle 36 of the main exchanger 4c so that, on leaving the condensation part 34 of said other exchanger or exchangers 41, the coolant fluid passes into the bottle 36 of the main exchanger 4c. Accordingly, the bottle 36 and the condensation part 34 of the main exchanger 4c are common to all the exchangers.

The condensation part 34 of the main exchanger 3c could include a single pass for the coolant fluid, symbolized by the arrow 40. The condensation part 34 of the other exchangers 41 of the heat exchange device 3 could include two passes for the coolant fluid, symbolized by the arrows 42, 44. By pass is meant a part of the heat exchange bundle in which the coolant fluid circulates in the same direction between two manifold portions of the corresponding exchanger, the direction of circulation of the coolant fluid being reversed from one pass to another in the case of a plurality of passes in the same exchanger. The subcooling area 38 of the main exchanger 4c, here with one pass, therefore has pass through it all the flow of coolant fluid. This being so, the coolant fluid is then in the liquid phase and the passage section necessary for its circulation is smaller. The head losses generated are therefore limited. For example, the passage section of the coolant fluid in the subcooling area 38 of the main exchanger 4c represents 10 to 30% of the passage section of the coolant fluid in the single pass 40 of the main exchanger 4c, preferably from 20 to 30% of the passage section of the coolant fluid in the single pass 40 of the main exchanger 4c, preferably 15%.

Here the main exchanger 4c is made up of the central exchanger and the other exchangers of the heat exchange device 3 are respectively made up of lateral exchangers 41.

The device according to the invention could further include flaps, not shown, for shutting off the passage of the flow of air F through the other exchangers 41. As will emerge more clearly later, a feature of this kind finds its particular benefit in the embodiments from figures 3 and 5 and 6.

In fact, in some cases, for example when moving, the requirements for thermal regulation of the battery 1 and/or air conditioning of the passenger compartment may remain low and the thermal power to be dissipated by means of the heat exchange device 3 is then limited. In such cases, it is advantageous to cause the coolant fluid to circulate only in the main exchanger 4c. It is equally advantageous to close the air passage flaps of the other exchangers 41. This in particular enables the aerodynamics of the vehicle to be improved.

Conversely, in the other case, for example when stopped, during recharging of the battery 1, in particular during fast charging, and/or, when travelling, when the requirements for air conditioning of the passenger compartment and the requirements for thermal regulation of the battery 1 are simultaneously high, the power to be dissipated by means of the heat exchange device 3 is high. In such cases, it is advantageous to cause the coolant fluid to circulate simultaneously in all the exchangers 4c, 41 of the heat exchange device.

In other words, said system for thermal management of the battery 1 is preferably configured to function in a first mode, corresponding for example to the first case mentioned in the preceding paragraph, in which said coolant fluid circulates in only one or only some of said exchangers 4 of the heat exchange device 3, here the central exchanger 4c, and in a second mode, corresponding for example to the second cases mentioned in the preceding paragraphs, in which the coolant fluid circulates in all said exchangers of the heat exchange device 3, here the central exchanger 4c and the lateral exchangers 41.

As shown in figure 5, the heat exchange device includes two valves 46, 48 for opening/closing the circulation of the coolant fluid respectively situated between one of the lateral exchangers 41 and the bottle 36 of the main exchanger 4c and between the other of the lateral exchangers 41 and the bottle 36 of the main exchanger 4c. Such valves are advantageously situated at the outlet of each of the lateral exchangers in order to limit the head losses upstream of heat exchange. Said valves 46, 48 enable a change from the first mode to the second referred to above and vice versa.

As shown in figure 6, the heat exchange device instead includes a single valve 50 for opening/closing the circulation of the coolant fluid, situated on a common branch feeding the bottle 36 of the main exchanger 4c from a connection point between tubes coming from each of the lateral exchangers 41.

As already mentioned throughout the foregoing description, the invention further concerns a method for thermal management of a battery, notably for fast cooling of said battery, utilizing a thermal management system as referred to above. Other applications of the heat exchange device described above are equally possible, in particular in the case of requiring a high thermal power and/or a high fluid flow rate, in particular in a restricted space .