FR3037639A1 - THERMAL MANAGEMENT DEVICE - Google Patents

Abstract

The present invention relates to a thermal management device (1) comprising an air conditioning loop (A) in which a refrigerant circulates, said air conditioning loop (A) comprising, in the fluid circulation direction, a compressor (3), a first heat exchanger (11), a first expansion device (21), a second heat exchanger (12), said thermal management device (1) further comprising a heat exchange loop (B) connected with said air conditioning loop (A), at least the compressor (3) being common to the air conditioning loop (A) and the heat exchange loop (B), said heat exchange loop (B) comprising, arranged in the flow direction of the coolant, a third heat exchanger (13) connected to a cold source, a second expansion device (22) and a fourth heat exchanger (14) connected to a hot source.

Description

The present invention relates to the field of thermal management in a motor vehicle and more particularly to the thermal management between a so-called hot source at high temperature, which emits heat energy, and a so-called cold source. receiver of heat energy. In order to transfer heat energy between a hot source and a cold source, it is known to use a heat exchange loop comprising a heat exchanger 10 in contact with each source and a pump allowing the setting in motion of a heat transfer fluid flowing between the two heat exchangers. For high temperature hot springs such as a heat engine, it is customary to use a heat transfer fluid having a high critical temperature in order to avoid the problems of cavitation and / or degraded operation of the pump of the loop. thermal management. Such hot springs can be used to help the heating including the cabin. However, the use of a refrigerant fluid, used in particular in an air conditioning loop, as heat transfer fluid in a heat exchange loop allowing the heat exchange between a hot source and a cold source may not be adequate, especially when the hot and cold sources are both at high temperature and have a low temperature difference. Indeed, at high temperature the cooling fluid (for example carbon dioxide) is in a supercritical state, that is to say that it has a temperature above its critical temperature. The pump used to set in motion said coolant can thus no longer be supplied with fluid in the liquid state and problems of cavitation and degraded operation may occur. It is therefore necessary to choose a heat transfer fluid whose critical temperature is greater than the temperature of at least the cold source within a specific heat exchange loop. The fact of having to use a specific heat exchange loop induces an increase in manufacturing costs, but also a reduction in the space available for other thermal management devices such as air conditioning. One of the aims of the present invention is therefore to at least partially overcome the drawbacks of the prior art and to propose a thermal management device allowing the heat exchange between a hot source at high temperature and a cold source, also at high temperature. temperature. The present invention therefore relates to a thermal management device 10 comprising an air conditioning loop in which a refrigerant circulates, said air conditioning loop comprising, in the direction of circulation of the fluid, a compressor, a first heat exchanger, a first cooling device. detent, a second heat exchanger, said thermal management device further comprising a heat exchange loop connected with said air conditioning loop, at least the compressor being common to the air conditioning loop and the heat exchange loop, said heat exchange loop comprising, disposed in the direction of flow of the coolant, a third heat exchanger connected to a cold source, a second expansion device and a fourth heat exchanger connected to a hot source. Due to the interconnection between the air conditioning loop and the heat exchange loop within the same thermal management device where the two loops share at least the compressor, heat exchanges between a hot source at the fourth level. A heat exchanger and a heat sink at the third heat exchanger can take place using the cooling fluid of the air conditioning loop. The fact that the refrigerant can undergo a pressure loss of between 0 and 5 bar at the second expansion device allows the compressor to put the coolant in motion in the heat exchange loop while spending the least energy possible. In addition, the coolant 30 can be used as a heat energy carrier between the hot source and the cold source even at high temperature, especially when the temperature of the cold source is at a temperature above the critical temperature of the refrigerant. Indeed, the compressor is not subject to cavitation problems or degraded operation if the refrigerant is in the gaseous state.

According to one aspect of the invention, the second expansion device is at least able to let the refrigerant fluid with a pressure loss of between 0 and 5 bar.

According to another aspect of the invention, the thermal management device further comprises a redirection device adapted to allow the circulation of the refrigerant fluid from the compressor in the air conditioning loop or in the heat exchange loop.

According to another aspect of the invention, the air conditioning loop comprises an internal heat exchanger. According to another aspect of the invention, the thermal management device comprises a dehumidifying accumulator disposed upstream of the compressor.

According to another aspect of the invention, the air-conditioning loop comprises, arranged between a third diversion point placed upstream of the first expansion device and a fourth diversion point placed downstream of the second heat exchanger, a fifth heat exchanger. and a third expansion device placed upstream of said fifth heat exchanger. According to another aspect of the invention, the connection between the air conditioning loop and the heat exchange loop is performed by a first bypass line between a first branch point disposed downstream of the compressor and a second branch point disposed upstream of said compressor.

According to another aspect of the invention, the third heat exchanger, the second expansion device and the fourth heat exchanger are arranged on the first bypass line, the first branch point being then disposed: 5 - between the compressor and the first heat exchanger, in the direction of flow of the coolant within the air conditioning loop, - between the compressor and the third heat exchanger, in the direction of circulation of the refrigerant within the exchange loop thermal.

According to another aspect of the invention, the third heat exchanger, the second expansion device and the fourth heat exchanger are also common to both the air conditioning loop and the heat exchange loop, the first point in the direction of flow of the coolant, the shunt is then placed between the fourth heat exchanger and the first heat exchanger.

According to another aspect of the invention, the thermal management device comprises: a second bypass line between a fifth bypass point placed in the direction of circulation of the refrigerant between the fourth heat exchanger and the first heat exchanger, and a sixth bypass point placed in the flow direction of the coolant between the first heat exchanger and the second heat exchanger, said second bypass line having a fourth expansion device, and 25 - a second device for redirecting the refrigerant fluid from the fourth heat exchanger to the first heat exchanger or to the second bypass line.

According to another aspect of the invention, the thermal management device is configured according to a so-called "heat energy recirculation" operating mode in which the cooling fluid circulates successively in the compressor, the third heat exchanger, the second expansion device, wherein the refrigerant fluid is limited to a relaxation, less than or equal to 5 bar, the fourth heat exchanger and returns to the compressor via the first bypass line. According to another aspect of the invention, the thermal management device is configured according to a so-called "air conditioning" operating mode in which the refrigerant circulates successively in the compressor, the first heat exchanger, the first expansion device, wherein said coolant undergoes complete expansion, and the second heat exchanger.

Other characteristics and advantages of the invention will appear more clearly on reading the following description, given by way of illustrative and nonlimiting example, and the appended drawings in which: FIG. 1 shows a schematic representation of a thermal management device according to a first embodiment; FIGS. 2, 3a and 3b show the thermal management device of FIG. 1 according to different modes of operation; FIG. 4 shows a schematic representation of a device of FIG. Thermal management according to a second embodiment, - Figures 5 to 7c show the thermal management device of Figure 4 according to different modes of operation. In the different figures, the identical elements bear the same reference numbers.

The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Simple features of different embodiments can also be combined to provide other embodiments. In the present description it is possible to index certain elements or parameters, such as for example first element or second element as well as first parameter 10 and second parameter or else first criterion and second criterion, etc. In this case, it is a simple indexing to differentiate and name elements or parameters or criteria close, but not identical. This indexing does not imply a priority of one element, parameter or criterion with respect to another, and it is easy to interchange such denominations without departing from the scope of the present description.

This indexation does not imply either an order in time for example to appreciate such or such criteria. In the present description, the term "placed upstream" means that one element is placed before another relative to the direction of circulation of the refrigerant. On the other hand, "downstream" means that one element is placed after another relative to the direction of circulation of the refrigerant fluid. As shown in the various figures, the thermal management device 1 according to the invention comprises an air conditioning loop A and a heat exchange loop B in which circulates a refrigerant fluid. The air-conditioning loop A comprises in particular in the direction of circulation of the fluid, a compressor 3, a first heat exchanger 11, a first expansion device 21, a second heat exchanger 12. The first heat exchanger 11 may be a heat exchanger placed in contact with the outside air, for example on the front face of a motor vehicle. The second heat exchanger 12 may in turn be a heat exchanger placed in a heating, ventilation and air conditioning (or HVAC) device so that it is in contact with the heat exchanger. a flow of air intended for the passenger compartment of the motor vehicle.

The air conditioning loop A may also include an internal heat exchanger 19 arranged so as to allow the heat exchange between the refrigerant at the outlet of the first heat exchanger 11 and the refrigerant at the outlet of the second heat exchanger 12. The air conditioning loop A may further comprise a dehumidifying accumulator 30 disposed upstream of the compressor 3. More particularly the dehumidifying accumulator 30 may be placed between the internal heat exchanger 19 and the second heat exchanger 12. The heat exchange loop B comprises, in the direction of circulation of the coolant, a third heat exchanger 13 connected to a cold source, a second expansion device 22, at least able to let the refrigerant fluid with a pressure loss between 0 and 5 bar, preferably 2 bar, and a fourth heat exchanger 14 connected a hot spring.

Cold source means an element of the motor vehicle that may need a heat energy input to be reheated. Such a cold source may for example be a flow of air towards the passenger compartment, batteries or engine that must be heated to reach an optimum operating temperature. By hot source means an element of the motor vehicle which is able to give heat energy to be cooled, this heat energy can be reused to heat the cold source. Such a hot source may for example be a hot battery, a heat engine, the exhaust gas, a thermal battery. The fourth heat exchanger 14 is not necessarily in direct contact with the hot source, it can in particular be connected to a cooling circuit 3037639 8 of said hot source, for example to the cooling circuit of a heat engine and / or of electrical components. The heat exchange loop B is connected with the air conditioning loop 5A so that at least the compressor 3 is common to both said air conditioning loop A and the heat exchange loop B. The connection between the air conditioning loop A and the heat exchange loop B is carried out by a first bypass line 51 between a first bypass point 101, 110 disposed downstream of the compressor 3 and a second bypass point 102 disposed upstream of said compressor 3 , more precisely upstream of the dehumidifying accumulator 30. The thermal management device 1 further comprises a redirection device adapted to allow the circulation of the refrigerant fluid from the compressor 3 in the air conditioning loop A or in the control loop. heat exchange B. This redirection device adapted to allow the flow of refrigerant from the compressor 3 in the air conditioning loop A or d in the heat exchange loop B, may for example be composed of a first stop valve 301 disposed on the heat exchange loop B and a second stop valve 302 20 disposed on the air conditioning loop A The opening or closing of one of said first 301 or second 302 shutoff valves determines whether the coolant can flow or not in the corresponding loop. The redirection device may also be ensured by the fact that one or more of the expansion devices may be able to block the flow of refrigerant fluid. Another possibility may also be that this redirection device may be a three-way valve disposed at the first branch point 101, 110. According to a particular embodiment, the air conditioning loop A may also comprise, arranged between a third bypass point 103 placed upstream of the first expansion device 21 and a fourth bypass point 104 placed downstream of the second heat exchanger 12, a fifth heat exchanger 15 and a third expansion device 23 placed upstream said fifth heat exchanger 15. The fifth heat exchanger 15 may be in contact with an element of the motor vehicle, in addition to the flow of air passing through a heating, ventilation and / or air conditioning device (also designated by the acronym HVAC which corresponds to the term "Heating, Ventilation, Air-Conditionning device" in English), including a cooling by Intermediate air conditioning loop may be necessary. This element is for example a battery of an electric or hybrid vehicle. According to a first embodiment illustrated in FIGS. 1 to 3b, the third heat exchanger 13, the second expansion device 22 and the fourth heat exchanger 14 are arranged on the first bypass line 51, the bypass point 101 being then disposed: - between the compressor 3 and the first heat exchanger 11, in the direction of circulation of the refrigerant fluid within the air conditioning loop A, - between the compressor 3 and the third heat exchanger 13, in the direction 20 in a second embodiment illustrated in FIGS. 4 to 7c, the third heat exchanger 13, the second expansion device 22 and the fourth heat exchanger 25 are connected to the heat exchange loop B. also common to both the air conditioning loop A and the heat exchange loop B. In this second embodiment, the tap point 110 is t then disposed, in the direction of circulation of the refrigerant, between the fourth heat exchanger 14 and the first heat exchanger 11.

According to its second embodiment illustrated in FIGS. 4 to 7c, the thermal management device 1 may also comprise: a second bypass line 52 between a fifth bypass point 105 placed in the direction of circulation of the refrigerant fluid Between the fourth heat exchanger 14 and the first heat exchanger 11, and a sixth bypass point 106 placed in the flow direction of the refrigerant between the first heat exchanger 11 and the second heat exchanger 12, said second bypass line 52 having a fourth expansion device 24, and a coolant redirection device from the fourth heat exchanger 14 to the first heat exchanger 11 or to the second bypass pipe 52. This device redirecting coolant from the fourth heat exchanger 14 to the first sample 11 or to the second bypass line 52, for example may be composed of a third stop valve 303 disposed between the fifth branch point 105 and the first heat exchanger 11 and the fourth expansion device 24 which would be able to block the flow of refrigerant, or a stop valve disposed on the second bypass line 52. Another possibility may also be that this redirection device is a three-way valve disposed at the fifth level. bypass point 105. The refrigerant circulating in the thermal management device 1 may for example be R744 (or carbon dioxide) or any other refrigerant known to those skilled in the art and used in the field. The present invention also relates to a thermal management installation comprising a thermal management device 1 as previously described. FIGS. 2, 3a and 3b, as well as FIGS. 5 to 7c, show different modes of operation of the thermal management device 1 in which the elements and conduits in which the cooling fluid circulates are shown in solid lines. Dashed lines are shown elements and conduits in which the coolant is not redirected or moving.

The thermal management device 1 can in particular be configured according to a so-called "heat energy recirculation" operating mode illustrated in FIGS. 2 and 5. In this operating mode, the cooling fluid circulates mainly in the heat exchange loop. B. The refrigerant circulates successively in the compressor 3, the third heat exchanger 13, the second expansion device 22, where the refrigerant undergoes a limited expansion, less than or equal to 5 bar, preferably 2 bar, the fourth exchanger 14 and returns to the compressor 3 via the first bypass line 51. Before returning to the compressor 3, the refrigerant can also pass through the dehumidifying accumulator 30 and the internal heat exchanger 19.

This particular mode of operation allows heat exchanges between the hot source located at the fourth heat exchanger 14 and the cold source located at the third heat exchanger 13. The fact that the refrigerant undergoes a limited relaxation , less than or equal to 5 bar, preferably 2 bar, allows the compressor 3 to set it in motion while spending as little energy as possible. In addition, the refrigerant can be used as a heat energy carrier between the hot source and the cold source even high temperature, especially when the temperature of the cold source is at a temperature above the critical temperature of the refrigerant. Indeed, the compressor 3 is not subject to cavitation problems or degraded operation if the refrigerant is in the gaseous state. If the thermal management device is according to the first embodiment as illustrated in Figure 2, the refrigerant circulates successively, more particularly in the compressor 3, passes through the first point of diversion 101 30 to flow in the first branch branch 51, and flows in the third heat exchanger 13, the second expansion device 22, wherein the refrigerant undergoes a limited expansion, less than or equal to 5 bar, preferably 2 bar. The refrigerant then circulates in the fourth heat exchanger 14, passes through second bypass point 102 and returns to the compressor 3.

If the thermal management device is according to the second embodiment illustrated in FIG. 5, the refrigerant circulates successively, more particularly, in the compressor 3, the third heat exchanger 13, the second expansion device 22, where the refrigerant undergoes a limited expansion, less than or equal to 5 bar, preferably 2 bar. The coolant then passes only through the first branch point 110, flows into the first branch branch 51, passes through second branch point 102 and returns to the compressor 3. When the thermal management device 1 is in the first mode of As described above, this embodiment can be configured according to a first so-called "air-conditioning" operating mode in which the refrigerant circulates in the air-conditioning loop A, as illustrated in FIG. 3a. The refrigerant then circulates successively in the compressor 3, the first heat exchanger 11, the first expansion device 21, where the refrigerant is undergoing complete expansion, and the second heat exchanger 12. decreasing the pressure sufficiently high in order to achieve an enthalpy cycle sufficient for a conventional and known air conditioning. More particularly, the refrigerant circulates in the compressor 3, passes through the first bypass point 101 and then flows into the first heat exchanger 11. The refrigerant can then pass through the internal heat exchanger 19 for the first time. passing through the first expansion device 21, wherein said refrigerant fluid undergoes complete relaxation. The refrigerant then circulates in the second heat exchanger 12, passes into the second branch point 102, can pass through the dehumidifying accumulator 30, cross a second time the internal heat exchanger 19 and finally join the compressor 3. When the thermal management device 1 is according to the second embodiment described above, the latter can be configured according to a second mode of operation called "air conditioning" in which the refrigerant circulates in the air conditioning loop A, as illustrated in Figure 6a. The refrigerant then circulates successively in the compressor 3, the third heat exchanger 13, the second expansion device 22, where the refrigerant retains its pressure, the fourth heat exchanger 14, the first heat exchanger 11, the first expansion device 21, wherein said refrigerant undergoes a complete expansion, and the second heat exchanger 12. In this embodiment, the second expansion device 22 is thus able to pass the refrigerant fluid without loss of pressure. For this, the second expansion device 22 may be an expansion valve having an opening sufficient to let the refrigerant fluid without loss of pressure or a conventional expansion valve having a bypass line. As before, the term "complete expansion" means a sufficiently large pressure drop in order to achieve an enthalpy cycle sufficient for conventional and known air-conditioning. More particularly, in this second so-called "air-conditioning" mode of operation, the refrigerant circulates in the compressor 3 and then in the third heat exchanger 13. At the third heat exchanger 13, the refrigerant does not exchange heat. 'heat energy. For example, if the third heat exchanger is placed in an HVAC, no airflow to the passenger compartment passes through it. The refrigerant then passes through the second expansion device 22, where the refrigerant retains its pressure, and the fourth heat exchanger 14. At the fourth heat exchanger, the cooling fluid may, for example, exchange heat energy with the refrigerant. hot source to undergo pre-cooling. The refrigerant then passes through the first branch point 3037639 14 110 and then flows into the first heat exchanger 11 where it is cooled and releases heat energy. The refrigerant may then pass through the internal heat exchanger 19 for the first time before passing through the first expansion device 21, where the refrigerant fluid undergoes complete expansion. The refrigerant then flows into the second heat exchanger 12, where it captures heat energy, passes into the second branch point 102, can pass through the dehumidifying accumulator 30, and through a second heat exchanger internal 19 to finally join the compressor 3.

According to the first one, in which the second mode of operation known as "air-conditioning", the refrigerant can also, after having passed through the first heat exchanger 11, circulate in the third expansion device 23, where said coolant undergoes an expansion, and then in the fifth heat exchanger 15 as shown in Figures 3b and 6b. In order to decide whether the coolant fluid 15 circulates or not within the third expansion device 23 and the fifth heat exchanger 15, said third expansion device 23 may be able to block the flow of refrigerant. It is also possible to imagine the presence of a stop valve between the third branch point 103 and the third expansion device 23.

When the thermal management device 1 is according to the second embodiment and comprises a second bypass line 52 as described above, said thermal management device 1 can also be configured according to a first operating mode called "pump heat "as shown in Figure 7a. In this operating mode, the refrigerant circulates successively in the compressor 3, the third heat exchanger 13, the second expansion device 22, where the refrigerant retains its pressure, the fourth heat exchanger 14, the fourth cooling device. 24, where the refrigerant undergoes a complete expansion, the first heat exchanger 11 and returns to the compressor 3 via the first bypass line 51. In this mode of operation, the refrigerant captures heat energy at the level of the first heat exchanger 11 and releases it at the level of the third heat exchanger 13. Still when the thermal management device 1 is according to the second embodiment and it comprises a second bypass line 52, said device thermal management 1 can also be configured according to a second mode of operation known as "heat pump r ", as illustrated in FIGS. 7b and 7c. In this second so-called "heat pump" mode of operation, the refrigerant circulates successively in the compressor 3, the third heat exchanger 13, the second expansion device 22 where said refrigerant fluid undergoes complete expansion. The refrigerant then circulates in the fourth heat exchanger 14, the fourth expansion device 24 where the coolant maintains a constant pressure, and the second heat exchanger 12. In this operating mode, the first expansion device 21 is thus 15 able to let the refrigerant fluid without loss of pressure. For this, the first expansion device 21 may be an expansion valve having an opening sufficient to let the refrigerant fluid without loss of pressure or a conventional regulator having a bypass line. In this operating mode, the refrigerating fluid captures heat energy at the third heat exchanger 13 and releases it at the level of the second heat exchanger 12. In this second mode of operation called "heat pump", and as illustrated in FIG. 7c, the coolant can also flow, after having passed through the fourth expansion device 24, into the third expansion device 23, where the refrigerant retains its pressure, and the fifth heat exchanger 15. Like the first expansion device 21, the third expansion device 23 is thus able to pass the refrigerant fluid without loss of pressure. For this, the third expansion device 23 may be an expansion valve having an opening sufficient to let the refrigerant fluid without loss of pressure or a conventional expansion valve having a bypass line.

In this particular mode of operation, the refrigerating fluid captures heat energy at the third heat exchanger 13 and releases it at the level of the second heat exchanger 12 and the fifth heat exchanger 15.

Thus, it is clear that because of the interconnection between the air conditioning loop A and the heat exchange loop B within the same thermal management device 1 and where the two loops share at least the compressor 3 , heat exchanges between a heat source at the fourth heat exchanger 14 and a cold source at the third heat exchanger 13 can take place and this using the refrigerant of the air conditioning loop A despite the fact that the cold source may be at a temperature above the critical temperature of said refrigerant. In addition, the particular architecture of the thermal management device 1 may also allow particular operating modes, especially in heat pump mode, where the heat energy reused at the second 12 and fifth heat exchangers is directly derived. from the hot spring.

Claims (10)

REVENDICATIONS1. Thermal management device (1) comprising an air conditioning loop (A) in which a refrigerant circulates, said air conditioning loop (A) comprising, in the direction of circulation of the fluid, a compressor (3), a first heat exchanger (11), a first expansion device (21), a second heat exchanger (12), characterized in that said thermal management device (1) further comprises a heat exchange loop (B) connected with said loop at least the compressor (3) being common to the air conditioning loop (A) and the heat exchange loop (B), said heat exchange loop (B) comprising, arranged in the flow direction of the coolant, a third heat exchanger (13) connected to a cold source, a second expansion device (22) and a fourth heat exchanger (14) connected to a hot source. 2. Thermal management device (1) according to claim 1, characterized in that the second expansion device (22) is at least able to let the refrigerant with a loss of pressure between 0 and 5 bar. 3. Thermal management device (1) according to one of the preceding claims, characterized in that it further comprises a redirection device adapted to allow the circulation of the refrigerant from the compressor (3) in the air conditioning loop (A) or in the heat exchange loop (B). 4. Thermal management device (1) according to one of the preceding claims, characterized in that the air conditioning loop (A) comprises an internal heat exchanger (19). 20 25 3037639 18 5. Thermal management device (1) according to one of the preceding claims, characterized in that it comprises a dehumidifying accumulator (30) disposed upstream of the compressor (3). 5 6. Thermal management device (1) according to one of the preceding claims, characterized in that the air conditioning loop (A) comprises disposed between a third branch point (103) placed upstream of the first expansion device (21). ) and a fourth bypass (104) downstream of the second heat exchanger (12), a fifth heat exchanger (15) and a third expansion device (23) upstream of said fifth heat exchanger (15) . 7. Thermal management device (1) according to one of the preceding claims, characterized in that the connection between the air conditioning loop (A) and the heat exchange loop (B) is performed by a first branch line ( 51) between a first branch point (101) disposed downstream of the compressor (3) and a second branch point (102) disposed upstream of said compressor (3). 8. Thermal management device (1) according to the preceding claim, characterized in that the third heat exchanger (13), the second expansion device (22) and the fourth heat exchanger (14) are arranged on the first pipe bypass (51), the first bypass point (101) being then arranged: - between the compressor (3) and the first heat exchanger (11), in the direction of circulation of the cooling fluid within the air conditioning loop (A), - between the compressor (3) and the third heat exchanger (13), in the direction of circulation of the refrigerant within the heat exchange loop (B). 9. Thermal management device (1) according to one of claims 1 to 7, characterized in that the third heat exchanger (13), the second expansion device (22) and the fourth heat exchanger (14). ) are also common to both the air conditioning loop (A) and the heat exchange loop (B), the first branch point (101) being then arranged, in the direction of flow of the coolant, between the fourth heat exchanger (14) and the first heat exchanger (11). 10. Thermal management device (1) according to the preceding claim, characterized in that it comprises: - a second bypass line (52) between a fifth bypass point (105) placed in the direction of flow of the refrigerant fluid, between the fourth heat exchanger (14) and the first heat exchanger (11), and a sixth branch point (106) placed in the direction of flow of the coolant between the first heat exchanger (11). ) and the second heat exchanger (12), said second bypass line (52) having a fourth expansion device (24), and - a second refrigerant redirection device from the fourth heat exchanger (14) to the first heat exchanger (11) or to the second bypass line (52).