Heat-treatment system for a vehicle

Abstract

The present invention relates to a heat-treatment system (1) for a vehicle, comprising a coolant circuit (2) and a heat-transfer fluid circuit (3), the coolant circuit (2) comprising a first heat exchanger (5) and a second heat exchanger (7), the heat-transfer fluid circuit (3) comprising a first loop (10), a first branch (14) and a second branch (15), the first loop (10) comprising the second heat exchanger (7) and a third heat exchanger (12), the first branch (14) comprising a fourth heat exchanger (19) configured for heat treatment of an electrical storage device of the vehicle, characterised in that the heat-transfer fluid circuit (3) comprises a third branch (23) fluidically connecting the first loop (10) to the first branch (14) and to the second branch (15).

Description

[0001] DESCRIPTION

[0002] Title of the invention: Vehicle heat treatment system

[0003] The present invention relates to the field of motor vehicles, and more particularly concerns a heat treatment system integrated within said motor vehicles.

[0004] Motor vehicles are commonly equipped with a refrigerant circuit and at least one heat transfer fluid circuit, both used to participate in a heat treatment of different areas or different components of the vehicle. It is particularly known to use the refrigerant circuit and / or the heat transfer fluid circuit to heat treat an air flow sent into the passenger compartment of the vehicle equipped with such a circuit. This heat treatment is carried out in particular by means of a circulation of the refrigerant within a ventilation, heating and / or air conditioning system arranged in the vehicle.

[0005] In another application of this circuit, it is known to use the heat transfer fluid circuit to cool components of the vehicle's powertrain, such as for example an electrical storage device, the latter being used to supply energy to an electric motor capable of setting the vehicle in motion. The heat treatment system thus supplies the energy capable of cooling the electrical storage device during its use in driving phases.

[0006] Several refrigerants have been used for this type of heat treatment system, such as Ri34a or Ri234yf. However, following new European standards, these refrigerants have been banned from use in Europe due to their environmental harm. For future heat treatment systems, it was therefore decided to use R290 as the refrigerant. However, R290 is pure propane. As a safety precaution, it is therefore essential to avoid circulating propane directly in the ventilation, heating and / or air conditioning system. Thus, it is known to heat treat the vehicle interior indirectly using the refrigerant, and only the heat transfer fluid then circulates within the ventilation, heating and / or air conditioning system.

[0007] It is known in particular to implement two heat exchangers ensuring the cooling of the heat transfer fluid so that the latter can heat treat the passenger compartment of the vehicle and an element of the vehicle's powertrain simultaneously, with a heat exchanger dedicated to each function.

[0008] Car manufacturers are constantly improving their vehicles. These improvements include reducing the space requirement and cost of the heat treatment system, while maintaining a variety of operating modes.

[0009] The present invention falls within this context and proposes as such a system for heat treatment of a vehicle, comprising a refrigerant circuit intended to be traversed by a refrigerant and a heat transfer fluid circuit intended to be traversed by a heat transfer fluid, the refrigerant circuit comprising at least one compression device, an expansion member, as well as a first heat exchanger and a second heat exchanger configured to carry out a heat exchange between the refrigerant and the heat transfer fluid, the heat transfer fluid circuit comprising a first loop, a first branch and a second branch, the first loop comprising a first pumping device, the second heat exchanger and a third heat exchanger configured to carry out a heat exchange between the heat transfer fluid and an interior air flow intended to be sent into a passenger compartment of the vehicle,the first branch extending between a first junction point and a first convergence point arranged on the first loop between the third heat exchanger and the first pumping device and comprising a second pumping device and a fourth heat exchanger configured to thermally treat an electrical storage device of the vehicle, the second branch extending between the first junction point and a second junction point arranged on the first branch between the fourth heat exchanger and the first convergence point, characterized in that the heat transfer fluid circuit comprises a third branch fluidically connecting the first loop to the first branch and to the second branch, the third branch starting at a first divergence point arranged on the first loop between the second heat exchanger and the third heat exchanger and extending to the first junction point.,

[0010] Such a heat treatment system according to the invention allows cooling of the passenger compartment of the vehicle and / or of the electrical storage device by pre-cooling the heat transfer fluid using a single heat exchanger which is the second heat exchanger. It is then possible to do without an additional heat exchanger and to distribute the cooled heat transfer fluid simultaneously to the third heat exchanger in order to cool the passenger compartment of the vehicle and to the fourth heat exchanger in order to cool the electrical storage device, the third branch ensuring a direct fluid connection between the second heat exchanger and the fourth heat exchanger.

[0011] The refrigerant is advantageously a fluid of type R290, that is to say propane, which is a two-phase refrigerant and which is compressed and circulated in the vapor state by the compression device. The refrigerant then passes through the first heat exchanger, the expansion member and the second heat exchanger in this order, in order to implement a thermodynamic cycle.

[0012] Thus, the high-pressure, high-temperature refrigerant fluid condenses as it passes through the first heat exchanger and transfers calories to the heat transfer fluid also circulating within the first heat exchanger. Then the refrigerant fluid is expanded by the expansion device and is then at low pressure and low temperature. Finally, the refrigerant fluid is evaporated as it circulates within the second heat exchanger and cools the heat transfer fluid also circulating within the second heat exchanger. The evaporated refrigerant fluid can then be compressed again by the compression device to begin a new cycle and participate in the functions of the heat treatment system.

[0013] Optionally, the refrigerant circuit may comprise an internal heat exchanger configured to carry out a heat exchange between the refrigerant circulating in the refrigerant circuit between the first heat exchanger and the expansion member and the refrigerant circulating in the refrigerant circuit between the second heat exchanger and the compression device. Such an internal heat exchanger allows an exchange of calories between the high-pressure refrigerant and the low-pressure refrigerant and thus regulates the thermodynamic balance within the refrigerant circuit while improving the performance of the thermodynamic cycle.

[0014] The refrigerant circuit may also include an accumulation device arranged between the second heat exchanger and the compression device. The accumulation device makes it possible, in the event of partial evaporation of the refrigerant, to retain a fraction of the refrigerant that remains liquid in order to prevent this liquid fraction from circulating to the compression device and damaging it.

[0015] The heat transfer fluid circulating in the heat transfer fluid circuit may, for example, be glycolated water. The latter is circulated in the first loop using the first pumping device and circulates within the second heat exchanger to be cooled by the low-pressure, low-temperature refrigerant, as described above.

[0016] Subsequently, the heat transfer fluid can continue its circulation in the first loop to circulate to the third heat exchanger. The latter is advantageously arranged within a ventilation, heating and / or air conditioning system and thus contributes to the air conditioning of the vehicle's passenger compartment. To do this, the interior air flow passes through the third heat exchanger and transfers its calories to the heat transfer fluid. The cooled interior air flow is then sent into the vehicle's passenger compartment to air condition it. Alternatively or simultaneously, at the outlet of the second heat exchanger, the heat transfer fluid circulates in the third branch from the first point of divergence, in order to subsequently circulate in the first branch and pass through the fourth heat exchanger in order to cool the electrical storage device.The latter may be at a very high temperature, for example following rapid recharging, and must therefore be cooled to avoid damage. The circulation of the heat transfer fluid can be assisted by the second pumping device. The first branch extends to the first convergence point, upstream of the second heat exchanger, so that the heat transfer fluid can join the first loop and be cooled again by the refrigerant within the second heat exchanger.

[0017] The second branch extends in parallel with a portion of the first branch extending between the first junction point and the second junction point, said portion comprising the second pumping device and the fourth heat exchanger. The second branch makes it possible in particular to recirculate heat transfer fluid from the second junction point to the first junction point, in order to use the calories captured within the fourth heat exchanger to heat the heat transfer fluid coming directly from the third branch and circulating upstream of the fourth heat exchanger. Such a configuration makes it possible to cool the electrical storage device to a moderately low temperature in order to avoid generating a malfunction thereof following excessively sudden cooling.

[0018] The third branch connecting the first loop to the first branch, and the latter also being connected to the first loop via the first convergence point, the fourth heat exchanger can therefore be supplied with heat transfer fluid cooled by the second heat exchanger.

[0019] According to a characteristic of the invention, the heat transfer fluid circuit comprises a second loop comprising a third pumping device, the first heat exchanger and a fifth heat exchanger configured to carry out a heat exchange between the heat transfer fluid and an air flow outside the passenger compartment of the vehicle. The second loop allows circulation of heat transfer fluid thanks to the third pumping device and can also be heated via the first heat exchanger thanks to the high pressure and high temperature refrigerant which also circulates therein. The fifth heat exchanger allows thermal treatment of the heat transfer fluid thanks to the outside air flow.Therefore, the fifth heat exchanger is ideally arranged at the front of the vehicle so that a phase of vehicle movement results in the generation of the flow of outside air circulating within the front of the vehicle and thus passing through the fifth heat exchanger.

[0020] According to a characteristic of the invention, the heat transfer fluid circuit comprises a fourth branch starting at a second point of divergence arranged on the second loop between the first heat exchanger and the fifth heat exchanger and ending at a second point of convergence arranged on the second loop between the fifth heat exchanger and the third pumping device, the fourth branch comprising a sixth heat exchanger configured to carry out a heat exchange between the heat transfer fluid and the interior air flow. The fourth branch is connected to the second loop on either side of the third pumping device and the first heat exchanger so that high-temperature heat transfer fluid can be circulated in the fourth branch.

[0021] The sixth heat exchanger, like the third heat exchanger, is advantageously arranged in the ventilation, heating and / or air conditioning installation mentioned above. The heat transfer fluid circulating within the sixth heat exchanger then transfers its calories to the interior air flow which then increases in temperature and circulates to the passenger compartment of the vehicle to heat the latter. Thus, when heating of the passenger compartment of the vehicle is requested, the heat transfer fluid circulates between the second loop and the fourth branch, is heated within the first exchanger and transfers its calories to the interior air flow within the sixth heat exchanger. According to a characteristic of the invention, the second point of divergence comprises a regulating member configured to regulate the flow of heat transfer fluid circulating towards the fifth heat exchanger and / or towards the sixth heat exchanger.The regulating organ may, for example, be a three-way valve comprising an inlet into which the heat transfer fluid heated within the first heat exchanger enters, and two outlets ensuring circulation to the fifth heat exchanger or to the sixth heat exchanger.

[0022] Advantageously, such a three-way valve is proportional, that is to say that it is possible to selectively distribute the heat transfer fluid to one and / or the other of the outlets of the regulating member. Such a distribution may be dependent on the need and may also vary over time. According to a characteristic of the invention, the heat transfer fluid circuit comprises a fifth branch extending between a third junction point arranged on the third branch and a fourth junction point arranged on the first branch between the second junction point and the first convergence point, the fifth branch comprising a fourth pumping device and a seventh heat exchanger configured to heat treat an electric motor of the vehicle.The fifth branch is fluidically connected to the first branch and the third branch and thus ensures a fluid connection between the second heat exchanger and the seventh heat exchanger, as well as between the fourth heat exchanger and the seventh heat exchanger.

[0023] The seventh heat exchanger provides heat treatment for the vehicle's electric motor via the heat transfer fluid. The electric motor may require heating, for example when starting it up in very low ambient temperatures. The electric motor is also likely to generate heat during operation, particularly when the vehicle is traveling at high speeds, and must therefore be cooled to prevent it from malfunctioning. The fourth pumping device allows the heat transfer fluid to circulate in the fifth branch.According to a characteristic of the invention, the heat transfer fluid circuit comprises a sixth branch and a seventh branch, the sixth branch extending between a fifth junction point arranged on the fifth branch between the third junction point and the fourth pumping device and a sixth junction point arranged on the second loop between the fifth heat exchanger and the second point of convergence, the seventh branch extending between a seventh junction point arranged on the fifth branch between the seventh heat exchanger and the fourth junction point and an eighth junction point arranged on the second loop between the second point of divergence and the fifth heat exchanger.The sixth branch and the seventh branch extend between the second loop and the fifth branch and allow a fluid connection between the fifth heat exchanger and the second heat exchanger and / or the fourth heat exchanger and / or the seventh heat exchanger. The sixth branch and the seventh branch allow dissipation of the calories captured by the heat transfer fluid within the second heat exchanger or the fourth heat exchanger or the seventh heat exchanger. This allows passive cooling of the heat transfer fluid and therefore thermal treatment requiring only the flow of outside air, which is particularly advantageous in terms of energy expenditure.

[0024] According to a characteristic of the invention, the sixth branch and / or the seventh branch are configured to allow circulation of the heat transfer fluid in a first circulation direction or in a second circulation direction opposite to the first circulation direction. Depending on which element of the heat treatment system is to be heat treated via heat dissipation within the fifth heat exchanger, the circulation within the sixth and / or the seventh branch can be carried out in one or other of the circulation directions.

[0025] According to a feature of the invention, the first branch and the second branch respectively comprise a first valve and a second valve configured to control the circulation of the heat transfer fluid in the first branch and in the second branch. Depending on the operating mode operated by the heat treatment system, access to the first branch and to the second branch is respectively dependent on the first valve and the second valve. This makes it possible, for example, to avoid involuntary bypassing of the fourth heat exchanger.

[0026] According to a feature of the invention, the second branch comprises an electric heating element. The electric heating element is an additional heat source allowing heating of the heat transfer fluid in order to carry out an additional heat treatment of one of the elements of the heat treatment system, for example for the purpose of heating the electrical storage device or evaporating the refrigerant fluid. The position of the electric heating element is advantageous because the second branch is arranged so that the electric heating element can be in fluid connection with the second heat exchanger, the fourth heat exchanger and the seventh heat exchanger.

[0027] According to a characteristic of the invention, the second branch is configured to allow circulation of the heat transfer fluid in a first circulation direction or in a second circulation direction opposite to the first circulation direction. Like the sixth branch and the seventh branch, the second branch also allows circulation of heat transfer fluid in both circulation directions, the circulation direction being dependent on the operating mode of the heat treatment system.

[0028] According to a characteristic of the invention, the first convergence point comprises a regulating element configured to regulate the flow rate of heat transfer fluid circulating within the third heat exchanger and / or in the first branch. The regulating element, like the regulating member, makes it possible to control a distribution of the fluid circulating towards the third heat exchanger or within the third branch. The distribution of heat transfer fluid is carried out according to the need, for example if cooling of the passenger compartment of the vehicle or of an element of the vehicle's powertrain is preferred. According to a characteristic of the invention, the seventh junction point comprises a regulating device. Such a regulating device may be a three-way valve comprising two open ways and one closed way.The three-way valve is configured so that, even if the heat transfer fluid does not circulate within any of said channels, the closed channel is selected so as not to disturb the circulation of the heat transfer fluid if it circulates in the vicinity of the regulation device.

[0029] The invention also covers a method for heat treatment of a vehicle, implemented by a heat treatment system as described previously, during which:

[0030] - the heat transfer fluid is circulated within the first loop,

[0031] - the heat transfer fluid circulating in the first loop is separated into two fractions of heat transfer fluid, a first fraction of heat transfer fluid circulating in the first loop and passing through the third heat exchanger, a second fraction of heat transfer fluid circulating in the third branch.

[0032] Such a heat treatment process guarantees simultaneous treatment of the vehicle's passenger compartment and one or more elements of its powertrain, with a single heat exchanger dedicated to cooling the heat transfer fluid via the refrigerant.

[0033] According to a characteristic of the process, during the process:

[0034] - the refrigerant is circulated in the refrigerant circuit,

[0035] - the second fraction of heat transfer fluid is circulated in the first branch via the third branch to pass through the fourth heat exchanger,

[0036] - at the outlet of the fourth heat exchanger, part of the second fraction is recirculated in the first branch upstream of the fourth heat exchanger via the second branch.

[0037] According to another characteristic of the process, during the process: the second fraction of heat transfer fluid is circulated in the second branch via the third branch to pass through the electric heating element.

[0038] These characteristics differ more generally with respect to different operating modes that can be implemented within the heat treatment system according to the invention.

[0039] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several examples of embodiment given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which:

[0040] [fig i] is a schematic representation of a heat treatment system according to the invention,

[0041] [fig 2] is a schematic representation of a first mode of operation of the heat treatment system,

[0042] [fig 3] is a schematic representation of a second mode of operation of the heat treatment system,

[0043] [fig 4] is a schematic representation of a third mode of operation of the heat treatment system,

[0044] [fig 5] is a schematic representation of a fourth mode of operation of the heat treatment system,

[0045] [fig 6] is a schematic representation of a fifth mode of operation of the heat treatment system,

[0046] [fig 7] is a schematic representation of a sixth mode of operation of the heat treatment system.

[0047] Figure 1 represents a heat treatment system 1 according to the invention, which can be integrated into a motor vehicle. This heat treatment system 1 is capable of providing heat treatment of the passenger compartment of the vehicle, but also heat treatment of various components of a powertrain of the vehicle. To do this, the heat treatment system i comprises a refrigerant circuit 2 within which a refrigerant circulates and a heat transfer fluid circuit 3 within which a heat transfer fluid circulates. In Figure 1, the refrigerant circuit 2 is shown in dot-and-dash lines while the heat transfer fluid circuit 3 is shown in solid lines.

[0048] The heat treatment system 1 is configured to operate different interactions between the heat transfer fluid and the refrigerant fluid in order to optimally heat treat the vehicle interior and the various components of the vehicle's powertrain. The heat transfer fluid may, for example, be glycolated water, while the refrigerant fluid may advantageously be a fluid of type R290, i.e. propane, meeting European environmental protection standards unlike other types of refrigerant fluid used for heat treatment.

[0049] The refrigerant circuit 2 is formed of a single closed path, provided with a compression device 4 circulating the refrigerant in the refrigerant circuit, a first heat exchanger 5, an expansion member 6 and a second heat exchanger 7. The first heat exchanger 5 and the second heat exchanger 7 are configured to carry out a heat exchange between the refrigerant circulating in the refrigerant circuit 2 and the heat transfer fluid circulating in the heat transfer fluid circuit 3. The expansion member 6 ensures an expansion of the refrigerant which then drops in pressure and temperature.

[0050] The refrigerant fluid thus follows a thermodynamic cycle by being initially compressed by the compression device 4 which increases the pressure and temperature of the refrigerant fluid. The refrigerant fluid is subsequently condensed within the first heat exchanger 5. The heat exchange occurring within the first heat exchanger 5 causes a drop in the temperature of the refrigerant fluid which is then condensed, while causing an increase in the temperature of the heat transfer fluid also circulating within the first heat exchanger 5. At the outlet of the first heat exchanger 5, the refrigerant fluid is expanded by the expansion member 6, thus causing a drop in pressure and temperature of said refrigerant fluid. Subsequently, the latter passes through the second heat exchanger 7.

[0051] The refrigerant fluid is evaporated within the second heat exchanger 7. The heat exchange occurring within the second heat exchanger 7 results in a heat input to the refrigerant fluid which is then evaporated, while causing a drop in the temperature of the heat transfer fluid also circulating within the second heat exchanger 7.

[0052] Advantageously, as illustrated in Figure 1, the refrigerant circuit 2 may also comprise an internal heat exchanger 8 and an accumulation device 9.

[0053] The internal heat exchanger 8 is configured to carry out a heat exchange between the refrigerant circulating between the first heat exchanger 5 and the expansion member 6, i.e. the high-pressure refrigerant, and the refrigerant circulating between the second heat exchanger 7 and the accumulation device 8. The internal heat exchanger 8 thus regulates the thermodynamic balance within the refrigerant circuit 2 while improving the performance of the thermodynamic cycle.

[0054] Since the compression device 4 is only capable of compressing refrigerant fluid in the gaseous state, the accumulation device 9 arranged upstream makes it possible to retain a liquid fraction of the refrigerant fluid in the event of partial evaporation within the second heat exchanger 7 and / or the internal heat exchanger 8. This prevents refrigerant fluid in the liquid state from passing through the compression device 4, which could cause it to malfunction.

[0055] The heat transfer fluid circuit 3 comprises a first loop 10 provided with a first pumping device 11, the second heat exchanger 7 and a third heat exchanger 12. The first pumping device 11 ensures the circulation of the heat transfer fluid in the first loop 10. As described previously, the second heat exchanger 7 guarantees a reduction in the temperature of the heat transfer fluid via heat exchange with the refrigerant.

[0056] The third heat exchanger 12 is configured to carry out a heat exchange between the heat transfer fluid and an interior air flow 13 passing through said third heat exchanger 12. The interior air flow 13 is subsequently intended to circulate to the passenger compartment of the vehicle. It is thus understood that the heat transfer fluid cools the interior air flow 13 passing through the third heat exchanger 12, and the cooled interior air flow 13 subsequently ensures the air conditioning of the passenger compartment of the vehicle. As a result, the third heat exchanger 12 is advantageously arranged within a ventilation, heating and / or air conditioning installation not illustrated.

[0057] The heat transfer fluid circuit 3 further comprises a first branch 14 and a second branch 15. The first branch 14 extends between a first junction point 16 and a first convergence point 17, the latter being arranged at the level of the first loop 10 between the third heat exchanger 12 and the first pumping device 11.

[0058] The first branch 14 comprises a second pumping device 18 and a fourth heat exchanger 19 configured to carry out a heat exchange between the heat transfer fluid circulating in the first branch 14 and an electrical storage device of the vehicle (not illustrated). The fourth heat exchanger 19 thus makes it possible to heat treat the electrical storage device if necessary. For example, it must be heated when the vehicle is started in the event of low ambient temperature. According to a reverse example, the electrical storage device is likely to release a lot of heat during its operation, for example following rapid recharging, and must therefore be cooled in this situation. The heating or cooling of the electrical storage device is therefore implemented by means of the heat transfer fluid circulating within the fourth heat exchanger 19.

[0059] The second branch 15 extends between the first junction point 16 and a second junction point 47 arranged on the first branch 14 between the fourth heat exchanger and the first convergence point 17. The second branch 15 comprises an electric heating element 20 ensuring heating of the heat transfer fluid circulating in the second branch 15. The electric heating element 20 constitutes an additional heat source if necessary. The first branch 14 and the second branch 15 also respectively comprise a first valve 21 and a second valve 22 authorizing or prohibiting the circulation of the heat transfer fluid in the first branch 14 and in the second branch 15.

[0060] The heat treatment system 1 according to the invention, more particularly the heat transfer fluid circuit 3, is characterized in that it comprises a third branch 23 extending between a first point of divergence 24 arranged on the first loop 10 between the second heat exchanger 7 and the third heat exchanger 12, and the first junction point 16 at which the first branch 14 and the second branch 15 extend. The third branch 23 makes it possible to form a closed fluid connection between the first loop 10 and the first branch 14. Thus, the heat transfer fluid can circulate between the second heat exchanger 7 and the fourth heat exchanger 19.

[0061] The cooled heat transfer fluid within the second heat exchanger 7 can therefore circulate to the third heat exchanger 12 to cool the passenger compartment of the vehicle, or to the fourth heat exchanger 19 to cool the electrical storage device, or even separate into two fractions to implement the two aforementioned functions simultaneously. This makes it possible to implement a refrigerant circuit 2 with a single heat exchanger having the function of cooling the heat transfer fluid instead of implementing two paths each comprising an expansion member and a heat exchanger dedicated to cooling the heat transfer fluid. The refrigerant circuit 2 is then more compact, while maintaining a multiplicity of operating modes of the heat treatment system 1.

[0062] In order to improve the distribution of the heat transfer fluid, the first convergence point 17 may comprise a regulating element 46 which may be in the form of a proportional three-way valve. The regulating element 46 makes it possible to control the distribution of the heat transfer fluid flow rate between the first loop 10 and the first branch 14 according to the priority requirement.

[0063] The heat transfer fluid circuit 3 also comprises a second loop 25. The latter comprises a third pumping device 26, the first heat exchanger 5, as well as a fifth heat exchanger 27 configured to carry out a heat exchange between the heat transfer fluid and an outside air flow 28 which is not intended to be sent into the passenger compartment of the vehicle. In order to be positioned at a path of the outside air flow 28, the fifth heat exchanger 27 may for example be arranged at a front face of the vehicle. The fifth heat exchanger thus allows for example a dissipation of the calories of the heat transfer fluid using the outside air flow 28.

[0064] The heat transfer fluid circuit 3 also comprises a fourth branch 29 extending between a second point of divergence 30 arranged on the second loop 25 between the first heat exchanger 5 and the fifth heat exchanger 27, and a second point of convergence 31 arranged on the second loop 25 between the fifth heat exchanger 27 and the third pumping device 26.

[0065] The fourth branch 29 comprises a sixth heat exchanger 32 which, like the third heat exchanger 12, is configured to carry out a heat exchange between the heat transfer fluid and the interior air flow 13. As described previously, the first heat exchanger 5 allows heating of the heat transfer fluid. Thus, the sixth heat exchanger 32 allows the heat transfer fluid to transfer its calories to the interior air flow 13 which is subsequently sent into the passenger compartment of the vehicle to heat it. The sixth heat exchanger 32 is therefore also advantageously arranged within the ventilation, heating and / or air conditioning installation mentioned above.

[0066] The second point of divergence 30 may comprise a regulating member 33 which, like the regulating element 24, may be in the form of a proportional three-way valve allowing selection of the distribution between the heat transfer fluid circulating towards the fifth heat exchanger 27 or towards the sixth heat exchanger 32 depending on the requirement.

[0067] The heat transfer fluid circuit 3 is also equipped with a fifth branch 34 extending between a third junction point 35 arranged on the third branch 23, and a fourth junction point 36 arranged on the first branch 14 between the second junction point 47 and the first convergence point 17.

[0068] The fifth branch 34 comprises a fourth pumping device 37 and a seventh heat exchanger 38 configured to heat treat an electric motor with the heat transfer fluid. Depending on the situation, the electric motor must be heated, for example when starting the vehicle, or cooled, for example in the event of extreme heat release due to high vehicle speed.

[0069] Finally, the heat transfer fluid circuit comprises a sixth branch 39 and a seventh branch 40. The sixth branch 39 extends between a fifth junction point 41 arranged on the fifth branch 34 between the third junction point 35 and the fourth pumping device 37, and a sixth junction point 42 arranged on the second loop 25 between the fifth heat exchanger 27 and the second convergence point 31.

[0070] The seventh branch 40 extends between a seventh junction point 43 arranged on the fifth branch 34 between the seventh heat exchanger 38 and the fourth junction point 36, and an eighth junction point 44 arranged on the second loop 25 between the second divergence point 30 and the fifth heat exchanger 27.

[0071] The sixth branch 39 and the seventh branch 40 ensure a fluid connection between the fifth heat exchanger 27 and the fourth heat exchanger 19 and / or the seventh heat exchanger 38. This mainly makes it possible to implement passive heat dissipation of the calories from the electric motor and / or the electrical storage device using the outside air flow 28. The seventh junction point 43 may comprise a regulation device 45 which may be a three-way valve and ensuring participation in a circulation of the heat transfer fluid corresponding to the desired operating mode.

[0072] Figures 2 to 7 each illustrate a particular operating mode of the heat treatment system 1. The list of these operating modes is not exhaustive and a plurality of other operating modes not illustrated may be implemented within the heat treatment system 1. For each of Figures 2 to 7, the solid lines indicate fluid circulation while the dotted lines represent an absence of fluid circulation. The direction of fluid circulation is also represented by arrows.

[0073] For the operating modes illustrated in Figures 2 to 6, the refrigerant circulates in the refrigerant circuit 2 according to the single loop illustrated in each figure. The refrigerant circulation is represented by thick solid lines when the refrigerant is at high pressure, and by thin solid lines when the refrigerant is at low pressure.

[0074] Thus, for each operating mode illustrated in Figures 2 to 6, the refrigerant is circulated and compressed by the high-pressure compression device 4. The refrigerant then passes through the first heat exchanger 5 while being at high temperature and therefore transfers its calories to the heat transfer fluid which also circulates within the first heat exchanger 5. This heat exchange makes it possible, on the one hand, to heat the heat transfer fluid, and on the other hand to cool and condense the refrigerant in order to implement the thermodynamic cycle of the refrigerant.

[0075] At the outlet of the first heat exchanger 5, the refrigerant is at least partially condensed and circulates to the internal heat exchanger 8 where it is further cooled by the low-pressure refrigerant also circulating within the internal heat exchanger 8. This heat exchange improves the thermodynamic balance of the refrigerant and also facilitates the expansion of the high-pressure refrigerant thereafter.

[0076] The refrigerant fluid, at the outlet of the internal heat exchanger 8, is expanded by the expansion member 6. The refrigerant fluid is therefore now at low pressure and low temperature and then passes through the second heat exchanger 7. The refrigerant fluid captures the calories from the heat transfer fluid which also circulates within the second heat exchanger 7. This heat exchange makes it possible, on the one hand, to cool the heat transfer fluid, and on the other hand to heat and evaporate the refrigerant fluid in order to complete the thermodynamic cycle of the refrigerant fluid.

[0077] At the outlet of the second heat exchanger 7, the low-pressure refrigerant circulates in the internal heat exchanger 8 and is heated by the high-pressure refrigerant. The low-pressure refrigerant then circulates to the accumulation device 9 where a potential liquid fraction of refrigerant is retained, then is compressed again by the compression device 4.

[0078] As mentioned previously, the circulation of the refrigerant fluid in the refrigerant circuit 2 is identical for the operating modes illustrated for figures 2 to 6. Only the circulation of the heat transfer fluid in the heat transfer fluid circuit 3 will therefore be described subsequently for each of said operating modes.

[0079] Figure 2 represents a first mode of operation of the heat treatment system 1. This first mode of operation has the objective of dehumidifying the interior air flow 13 intended to be sent into the passenger compartment of the vehicle. The dehumidification consists of circulating heat transfer fluid both within the third heat exchanger 12 and the sixth heat exchanger 32 in order to dehumidify the interior air flow 13. This method avoids sending a humid air flow into the passenger compartment which can cause several disadvantages such as the formation of fog on the windows of the vehicle which can impair visibility, or even discomfort for the occupants of the passenger compartment of the vehicle. For this first mode of circulation, the heat transfer fluid circulates in particular within the first loop 10.After being circulated by the first pumping device n, the heat transfer fluid is cooled within the second heat exchanger 7 by the low-pressure refrigerant, then circulates to the first divergence point 24 where it separates into two fractions. A first fraction of heat transfer fluid continues its circulation in the first loop 10 to the third heat exchanger 12 in order to cool the interior air flow 13 passing through the third heat exchanger 12.

[0080] A second fraction of heat transfer fluid circulates in the third branch 23 then in a portion of the fifth branch 34 up to the fifth junction point 41 to circulate in the sixth branch 39 until it joins the second loop 25 and passes through the fifth heat exchanger 27 so that the outside air flow 28 heats the second fraction. Subsequently, the second fraction circulates in the seventh branch 40, then in the fifth branch 34 towards the fourth junction point 36 thanks to the regulating device 45, then joins the first convergence point 17 via the first branch 14. The two fractions therefore join at the first convergence point 17 and the regulating element 46 allows flow control between the two fractions in order to regulate the overall temperature as efficiently as possible.Separating the heat transfer fluid into two fractions makes it possible to optimize the heating thereof through the third heat exchanger 12 and the fifth heat exchanger 27, with the aim of optimizing the thermodynamic cycle of the refrigerant fluid by promoting its evaporation within the second heat exchanger 7.

[0081] In parallel, another circulation of the heat transfer fluid is also implemented within the heat transfer fluid circuit 3, more particularly at the level of the fourth branch 29. The heat transfer fluid is circulated by the third pumping device 26 and passes through the first heat exchanger 5 to be heated by the high-pressure refrigerant. The heated heat transfer fluid then circulates to the second point of divergence 30 where the regulating member 33 directs it entirely within the fourth branch. The heated heat transfer fluid then passes through the sixth heat exchanger 32. By circulating within the sixth heat exchanger 32, the heat transfer fluid then heats the interior air flow 13. At the outlet of the sixth heat exchanger 32, the heat transfer fluid reaches the point of convergence 31 and is again pumped by the third pumping device 26.

[0082] Thus, before being sent into the passenger compartment of the vehicle, the interior air flow 13 is first cooled by passing through the third heat exchanger 12. The cooling of the interior air flow 13 makes it possible to condense the humidity present therein and to retain it. The interior air flow 13 thus leaves the third heat exchanger 12 cold and dry.

[0083] Then, the objective being to heat the passenger compartment of the vehicle while dehumidifying it, the interior air flow 13 passes through the sixth heat exchanger 32 to be heated there. The interior air flow 13 is thus sent into the passenger compartment of the hot and dry vehicle.

[0084] Figure 3 represents a second mode of operation of the heat treatment system 1, the purpose of which is to heat the passenger compartment of the vehicle. To do this, as described for the second mode of operation, the heat transfer fluid circulates in a portion of the second loop 25 and in the fourth branch 29 to be heated by the refrigerant fluid within the first heat exchanger 5 then to heat the interior air flow 13 by circulating within the sixth heat exchanger 32.

[0085] However, the thermodynamic cycle must be completed by evaporation within the second heat exchanger 7. Unlike the first embodiment, the heat transfer fluid cannot be heated by the interior air flow 13 within the third heat exchanger 12 because dehumidification is not required.

[0086] To overcome this, the heat transfer fluid circulated by the first pumping device 11 is cooled within the second heat exchanger 7 then circulates entirely in the third branch 23 and separates into two fractions at the third junction point 35. The first fraction of heat transfer fluid continues its circulation in the third branch 23 up to the first junction point 16.

[0087] The first valve 21 is closed while the second valve 22 is open, so that the first fraction circulates in the second branch 15 to be heated by the electric heating element 20 which allows a transfer of calories in place of the interior air flow 13 as illustrated in the first operating mode.

[0088] The circulation of the second fraction is identical to that described for the first operating mode. The second fraction circulates in a portion of the fifth branch 34 up to the fifth junction point 41 to then circulate in the sixth branch 39 until it reaches the second loop 25 and passes through the fifth heat exchanger 27 so that the outside air flow 28 heats the second fraction. Subsequently, the second fraction circulates in the seventh branch 40, then in the fifth branch 34 towards the fourth junction point 36 thanks to the regulation device 45.

[0089] The two fractions join at the fourth junction point 36 and then join the first loop 10 thanks to the regulating element 46. Here the evaporation of the refrigerant fluid within the second heat exchanger 7 is done on the one hand passively within the fifth heat exchanger 27 thanks to the flow of outside air 28, on the other hand via the electric heating element 20 by circulating a part of the heat transfer fluid within the second branch 15.

[0090] Figure 4 represents a third mode of operation of the heat treatment system 1 according to the invention. This third mode of operation consists of cooling both the passenger compartment of the vehicle and the electrical storage device. As illustrated in Figure 2, the heat transfer fluid circulating in the first loop 10 separates into two fractions at the first point of divergence 24. Such a mode of operation is part of a context of implementation of a heat treatment method during which the heat transfer fluid separates into two fractions, here ensuring simultaneous heat treatment of the passenger compartment of the vehicle and of an element of the vehicle's powertrain using a single heat exchanger operating a cooling of the heat transfer fluid via the refrigerant.

[0091] The first fraction continues its circulation in the first loop 10 until it passes through the third heat exchanger 12 so that the interior air flow 13 is cooled and is subsequently sent into the passenger compartment to cool it.

[0092] The second fraction circulates in the third branch 23 then in the first branch 14 to pass through the fourth heat exchanger 19 in order to cool the electrical storage device.

[0093] At the outlet of the fourth heat exchanger 19, the second fraction circulates to the second junction point 47 from which a part of the second fraction will circulate in the second branch 15, circulates within the electric heating element 20 without consequence because the latter is inactive, then rejoins the first branch 14 via the first junction point 16. Such recirculation makes it possible to substantially heat the heat transfer fluid coming directly from the second heat exchanger 17 with heat transfer fluid having already passed through the fourth heat exchanger 19 and which is therefore at a higher temperature. The objective of this configuration is to circulate heat transfer fluid at a moderately low temperature in the fourth heat exchanger 19 so as not to create a malfunction of the electrical storage device by cooling it too abruptly.As a result, both the first valve 21 and the second valve 22 are open.

[0094] This configuration also makes it possible to see that the second branch 15 allows the circulation of heat transfer fluid in both circulation directions. Indeed, in this third circulation mode, the heat transfer fluid circulates in the second branch 15 in a circulation direction opposite to the circulation direction as illustrated for example in FIG. 3. Thus, the heat transfer fluid can circulate in the second branch 15 in one or other of the circulation directions depending on the active operating mode. With the exception of the portion of heat transfer fluid circulating in the second branch 15, the second fraction, at the outlet of the fourth heat exchanger 19, circulates in the first branch 14 until it joins the first fraction at the first convergence point 17.

[0095] To complete the thermodynamic cycle, the refrigerant fluid must be condensed within the first heat exchanger 5. To do this, the heat transfer fluid also circulates within the second loop 25 to capture the calories from the refrigerant fluid within the first heat exchanger 5. This being done, the heat transfer fluid continues its circulation exclusively in the second loop 25 up to the fifth heat exchanger 27 so that the captured calories are dissipated via the outside air flow 28. The heat transfer fluid then returns to the first heat exchanger 5 still circulating within the second loop 25.

[0096] Figure 5 represents a fourth mode of operation of the heat treatment system 1 according to the invention. This fourth mode of operation makes it possible to simultaneously cool the passenger compartment of the vehicle, the electrical storage device and the electric motor.

[0097] The circulation of the heat transfer fluid passing through the second heat exchanger 7 to be cooled there is identical to what was described in FIG. 4, with a first fraction cooling the interior air flow 13 by circulating within the third heat exchanger 12 and a second fraction cooling the electrical storage device by circulating within the fourth heat exchanger 19 with a part recirculating via the second branch 15 so as not to carry out cooling with a heat transfer fluid that is too cold.

[0098] Also as for the previous mode of operation, the heat transfer fluid circulates in the second loop 25 to condense the refrigerant fluid by capturing its calories within the first heat exchanger 5. These calories are then dissipated by the outside air flow 28 when the heat transfer fluid circulates in the second loop 25 until it passes through the fifth heat exchanger 27. The difference with the previous mode of operation is that at the outlet of the fifth heat exchanger 27, the heat transfer fluid is divided into two fractions at the sixth junction point 42. A first fraction continues its circulation in the second loop 25 until it reaches the third pumping device 26.

[0099] A second fraction circulates within the sixth branch 39 in order to join the fifth branch 34 via the fifth junction point 41. The circulation of said second fraction is implemented by the fourth pumping device 37. The second fraction thus passes through the seventh heat exchanger 38 in order to cool the electric motor. This mode of operation only applies when the electric motor must be cooled moderately with heat transfer fluid whose calories have been dissipated by the external air flow 28.

[0100] At the outlet of the seventh heat exchanger 38, the second fraction circulates to the seventh junction point 43 where the regulation device 45 makes it circulate within the seventh branch 40 until it joins the second loop 25 and the first fraction via the eighth junction point 44. The calories of the heat transfer fluid are subsequently dissipated again by the flow of outside air 28 by circulating within the fifth heat exchanger 27.

[0101] This fourth operating mode makes it possible to observe that, just like the second branch 15, the sixth branch 39 and the seventh branch 40 also allow circulation of heat transfer fluid in both circulation directions. Indeed, as illustrated in FIG. 5, the heat transfer fluid circulates in the sixth branch 39 and in the seventh branch 40 in a circulation direction opposite to the circulation direction of the heat transfer fluid in these same two branches when it is for example the first circulation mode which is active, as illustrated in FIG. 2. Thus, the heat transfer fluid can circulate in the sixth branch 39 and in the seventh branch 40 in one or other of the circulation directions depending on the active operating mode. FIG. 6 represents a fifth operating mode of the heat treatment system 1 according to the invention.This involves dehumidifying the vehicle's interior while also cooling the electrical storage device.

[0102] The heat transfer fluid circulating within the first heat exchanger 5 is heated by the high-pressure refrigerant and is separated into two fractions at the second point of divergence 30 by means of the regulating member 33 which makes it possible to determine the quantity of heat transfer fluid in each of said fractions. The first fraction circulates in the fourth branch 29 and transfers its calories to the internal air flow 13 by circulating within the sixth heat exchanger 32. The second fraction continues its circulation in the second loop 25 to the fifth heat exchanger 27 so that the calories captured by the second fraction in the first heat exchanger 5 are dissipated by the external air flow 28 within the fifth heat exchanger 27. The two fractions subsequently join at the second point of convergence 31.

[0103] At the second heat exchanger 7, the heat transfer fluid is cooled and circulates to the first point of divergence 24 to also be separated into two fractions. The first fraction continues its circulation in the first loop 10 to pass through the third heat exchanger 12 and thus cool the interior air flow 13. The dehumidification function is therefore well implemented here because the interior air flow 13 is initially cooled by the heat transfer fluid circulating in the third heat exchanger 12, then is heated by the heat transfer fluid circulating in the sixth heat exchanger 32.

[0104] The second fraction formed at the first point of divergence 24 circulates in the third branch 23, then in the first branch 14 by being pumped into the second pumping device 18. The second fraction then circulates within the fourth heat exchanger 19 in order to cool the electrical storage device, then continues its circulation until it joins the first loop 10 via the first point of convergence 17. As illustrated in FIG. 6, the first valve 21 is open while the second valve 22 is closed. Depending on the temperature of the heat transfer fluid and / or the temperature of the electrical storage device, recirculation of the heat transfer fluid via the second branch 15 is not necessarily necessary. However, it is possible to implement the fifth operating mode with recirculation of the heat transfer fluid via the second branch 15, as illustrated for example in FIGS. 4 and 5.

[0105] Figure 7 represents a sixth mode of operation of the heat treatment system 1 according to the invention. This sixth mode of operation is particular because unlike the previous modes of operation, the refrigerant circuit 2 is inactive and the refrigerant therefore does not circulate. Thus, this sixth embodiment consists of heating the passenger compartment of the vehicle implemented in an emergency, for example in the event of a breakdown of the refrigerant circuit 2. This mode of operation is also part of the heat treatment process during which the heat transfer fluid separates into two fractions.

[0106] In this mode, the heat transfer fluid is circulated by the first pumping device 11 and passes through the second heat exchanger 7 without consequence because the refrigerant circuit 2 is inactive. The heat transfer fluid separates into two fractions at the first point of divergence 24. The first fraction continues its circulation in the first loop 10 and circulates within the third heat exchanger 12 before joining the second fraction at the first point of convergence 17.

[0107] The second fraction circulates in the third branch 23 up to the first junction point 16, then circulates exclusively in the second branch 15. In this operating mode, the first valve 21 is closed while the second valve 22 is open. By circulating in the second branch 15, the second fraction is heated by the electric heating element 20, then joins the first fraction at the first convergence point 17 via the first branch 14. It is thus understood that here, the heat transfer fluid accumulates calories via the second fraction heated by the electric heating element 20, and subsequently releases these calories via the first fraction circulating within the third heat exchanger 12. The latter, normally used to cool the interior air flow 13, is exceptionally used here to heat the interior air flow 13 in a manner specific to this sixth operating mode.

[0108] Other operating modes not illustrated are also operational thanks to the heat treatment system 1 according to the invention. In a non-exhaustive manner, among the functions not illustrated, it is for example possible to intensely cool the electric motor by fluidly connecting the second heat exchanger 7 to the seventh heat exchanger 38, to passively cool the electrical storage device by fluidly connecting the fourth heat exchanger 19 to the fifth heat exchanger 27, or to heat the electrical storage device with the heat released by the electric motor by fluidly connecting the fourth heat exchanger 19 to the seventh heat exchanger 38.

[0109] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention.

[0110] The invention, as just described, achieves the aim it set for itself, and makes it possible to propose a heat treatment system capable of implementing a plurality of operating modes by comprising only a single heat exchanger dedicated to the cooling of a heat transfer fluid via a refrigerant fluid. Variants not described here could be implemented without departing from the context of the invention, provided that, in accordance with the invention, they comprise a heat treatment system in accordance with the invention.

Claims

CLAIMS 1- Heat treatment system (1) of a vehicle, comprising a refrigerant circuit (2) intended to be traversed by a refrigerant and a heat transfer fluid circuit (3) intended to be traversed by a heat transfer fluid, the refrigerant circuit (2) comprising at least one compression device (4), an expansion member (6), as well as a first heat exchanger (5) and a second heat exchanger (7) configured to carry out a heat exchange between the refrigerant and the heat transfer fluid, the heat transfer fluid circuit (3) comprising a first loop (10), a first branch (14) and a second branch (15), the first loop (10) comprising a first pumping device (11), the second heat exchanger (7) and a third heat exchanger (12) configured to carry out a heat exchange between the heat transfer fluid and an interior air flow (13) intended to be sent into a passenger compartment of the vehicle,the first branch (14) extending between a first junction point (16) and a first convergence point (17) arranged on the first loop (10) between the third heat exchanger (12) and the first pumping device (11) and comprising a second pumping device (18) and a fourth heat exchanger (19) configured to thermally treat an electrical storage device of the vehicle, the second branch (15) extending between the first junction point (16) and a second junction point (47) arranged on the first branch (14) between the fourth heat exchanger (19) and the first convergence point (17), characterized in that the heat transfer fluid circuit (3) comprises a third branch (23) fluidically connecting the first loop (10) to the first branch (14) and to the second branch (15),the third branch (23) starting at a first point of divergence (24) arranged on the first loop (10) between the second heat exchanger (7) and the third heat exchanger (12) and extending to the first junction point (16)., 2- Heat treatment system (1) according to claim 1, in which the heat transfer fluid circuit (3) comprises a second loop (25) comprising a third pumping device (26), the first exchanger thermal (5) and a fifth heat exchanger (27) configured to carry out a heat exchange between the heat transfer fluid and an external air flow (28) to the passenger compartment of the vehicle. 3- Heat treatment system (1) according to claim 2, wherein the heat transfer fluid circuit (3) comprises a fourth branch (29) starting at a second point of divergence (30) arranged on the second loop (25) between the first heat exchanger (5) and the fifth heat exchanger (27) and ending at a second point of convergence (31) arranged on the second loop (25) between the fifth heat exchanger (27) and the third pumping device (26), the fourth branch (29) comprising a sixth heat exchanger (32) configured to carry out a heat exchange between the heat transfer fluid and the interior air flow (13). 4- Heat treatment system (1) according to the preceding claim, wherein the second point of divergence (30) comprises a regulating member (33) configured to regulate the flow rate of heat transfer fluid circulating towards the fifth heat exchanger (27) and / or towards the sixth heat exchanger (32). 5- Heat treatment system (1) according to claim 3 or 4, wherein the heat transfer fluid circuit (3) comprises a fifth branch (34) extending between a third junction point (35) arranged on the third branch (23) and a fourth junction point (36) arranged on the first branch (14) between the second junction point (47) and the first convergence point (17), the fifth branch (34) comprising a fourth pumping device (37) and a seventh heat exchanger (38) configured to heat treat an electric motor of the vehicle. 6- Heat treatment system (1) according to the preceding claim, in which the heat transfer fluid circuit (3) comprises a sixth branch (39) and a seventh branch (40), the sixth branch (39) extending between a fifth junction point (41) arranged on the fifth branch (34) between the third junction point (35) and the fourth pumping device (37) and a sixth junction point (42) arranged on the second loop (25) between the fifth heat exchanger (27) and the second point of convergence (31), the seventh branch (40) extending between a seventh junction point (43) arranged on the fifth branch (34) between the seventh heat exchanger (38) and the fourth junction point (36) and an eighth junction point (44) arranged on the second loop (25) between the second point of divergence (30) and the fifth heat exchanger (27). 7- Heat treatment system (1) according to the preceding claim, in which the sixth branch (39) and / or the seventh branch (40) are configured to allow circulation of the heat transfer fluid in a first direction of circulation or in a second direction of circulation opposite to the first direction of circulation. 8- Heat treatment system (1) according to any one of the preceding claims, wherein the first branch (14) and the second branch (15) respectively comprise a first valve (21) and a second valve (22) configured to control the circulation of the heat transfer fluid in the first branch (14) and in the second branch (15)- 9- Heat treatment system (1) according to any one of the preceding claims, wherein the second branch (15) comprises an electric heating element (20). 10- Heat treatment system (1) according to any one of the preceding claims, in which the second branch (15) is configured to allow circulation of the heat transfer fluid in a first circulation direction or in a second circulation direction opposite to the first circulation direction. 11- Heat treatment system (1) according to any one of the preceding claims, wherein the first convergence point (17) comprises a regulating element (46) configured to regulate the flow rate of heat transfer fluid circulating within the third heat exchanger (12) and / or in the first branch (14). 12- Heat treatment system (1) according to any one of claims 6 to 11, in combination with claim 6, wherein the seventh junction point (43) comprises a regulating device (45). 13- Method for heat treatment of a vehicle, implemented by a heat treatment system (i) according to any one of the preceding claims, during which: - the heat transfer fluid is circulated within the first loop (10), - the heat transfer fluid circulating in the first loop (10) is separated into two fractions of heat transfer fluid, a first fraction of heat transfer fluid circulating in the first loop (10) and passing through the third heat exchanger (12), a second fraction of heat transfer fluid circulating in the third branch (23). 14- Heat treatment method according to the preceding claim, during which: - the refrigerant fluid is circulated in the refrigerant fluid circuit (2), - the second fraction of heat transfer fluid is circulated in the first branch (14) via the third branch (23) to pass through the fourth heat exchanger (19), - at the outlet of the fourth heat exchanger (19), part of the second fraction is recirculated in the first branch (14) upstream of the fourth heat exchanger (19) via the second branch (15). 15- Heat treatment method according to claim 13, implemented by a heat treatment system (1) according to claim 9, during which: - the second fraction of heat transfer fluid is circulated in the second branch (15) via the third branch (23) to pass through the electric heating element (20).

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