Heating, Ventilation and/or Air Conditioning System Including Four Heat Exchangers

Abstract

The invention relates to a heating, ventilating and/or air conditioning device (1) comprising an A/C loop (6) inside which a refrigerating fluid FR circulates and a secondary loop (10) inside which a cooling fluid FC circulates. The said device (1) comprising a first heat exchanger (8) between the refrigerating fluid FR and the cooling fluid FC, a second heat exchanger (9) between the refrigerating fluid FR and the cooling fluid FC. The secondary loop comprises a third heat exchanger (14) between the cooling fluid FC and the air, and a fourth heat exchanger (15) between the cooling fluid FC and the air. The secondary loop (10) comprises derivation means (22) of the cooling fluid FC from an outlet point (21) of the cooling fluid FC outside the third heat exchanger (14) and an inlet point (23) of the cooling fluid FC inside the fourth heat exchanger (15).

Description

TECHNICAL FIELD OF THE INVENTION

The invention is in the field of heating, ventilation and/or air conditioning systems for a motor vehicle. It relates to such a system.

PRIOR ART

Motor vehicles are commonly equipped with a heating, ventilation and/or air conditioning systems in order to modify the aerothermal parameters of the air contained in the vehicle interior. This modification is achieved by delivering at least one air flow to the vehicle interior. The system includes a housing that is made of a plastic material and that is placed below an instrument panel of the vehicle. The housing is arranged so as to channel the circulation of the air flow from at least one air supply inlet to at least one air discharge outlet.

To cool the air flow before it is delivered to the vehicle interior, the system includes an air conditioning loop inside of which a coolant circulates, such as carbon dioxide known as R744. In general, the air conditioning loop includes at least one compressor, one evaporator and one heat exchanger, called a gas cooler. The compressor is capable of bringing the coolant to high pressure. The heat exchanger is arranged so that the coolant transfers heat to another fluid passing through the heat exchanger. The evaporator is provided in order to cool the air flow.

Document US 2008/0041071 (DENSO CORPORATION) describes such an air conditioning loop including two heat exchangers arranged one after the other on the air conditioning loop. An upstream heat exchanger is intended to enable an exchange of heat between the high-pressure coolant and a cooling liquid circulating inside a cooling circuit of a heat engine provided in the vehicle. A downstream heat exchanger, placed downstream of the upstream heat exchanger according to a direction of circulation of the coolant inside the air conditioning loop, is intended to enable an exchange of heat between the coolant coming from the upstream heat exchanger and a heat transfer fluid circulating inside a secondary loop.

Under certain conditions of use of the vehicle, it is useful to recover the heat transmitted by the high-pressure coolant to the cooling liquid and/or to the heat transfer liquid in order to heat the air flow before it is delivered to the vehicle interior. To this end, the housing comprises a channel inside of which is a first air heat exchanger involved in the secondary loop and a second air heat exchanger involved in the cooling circuit. The air flow passes through the first air heat exchanger, then the second air heat exchanger according to a direction of the air flow inside of the channel.

Such an architecture has numerous disadvantages.

The coolant is subjected inside the air conditioning loop to a thermodynamic cycle commonly described in a Mollier diagram. It is known to deduce from this diagram a coefficient of performance of said loop, designated by the acronym “COP” and defined as the ratio between a useful power recovered by the heat exchangers and energy consumed by the compressor in order to compress the coolant. It is constantly sought to have the coefficient of performance “COP” be as high as possible, for example on the order of 3 to 4, in order to provide the user of the vehicle with optimized thermal comfort, with minimal energy consumption. The architecture proposed by document US 2008/0041071 should be improved so as to obtain the highest possible “COP”, in particular between 3 and 4, while simplifying the system.

Such an architecture is not suitable for simultaneously achieving a high “COP” while providing effective and quick heating of the air flow.

SUBJECT MATTER OF THE INVENTION

The objective of this invention is to propose a heating, ventilation and/or air conditioning system including an air conditioning loop for cooling an air flow, in which the air conditioning loop offers the highest possible coefficient of performance “COP”, in particular between 3 and 4, while said system remains as simple as possible and enables, as the case may be, quick and effective heating of the air flow.

The system of this invention is a heating, ventilation and/or air conditioning system including an air conditioning loop inside of which a coolant circulates, and a secondary loop inside of which a heat transfer fluid circulates. Said system includes a first heat exchanger between the coolant FR and the heat transfer fluid FC, and a second heat exchanger between the coolant FR and the heat transfer fluid FC. The secondary loop includes a third heat exchanger between the heat transfer fluid FC and the air, and a fourth heat exchanger between the heat transfer fluid FC and the air. The secondary loop includes at least one means of bypass of the heat transfer fluid FC from an outlet point for the heat transfer fluid FC leaving the third heat exchanger to an inlet point for the heat transfer fluid FC entering the fourth heat exchanger.

The outlet point is advantageously connected to a mid-point located on the secondary loop between the first heat exchanger and the second heat exchanger.

The bypass means consist, for example, of a “Y” channel, including an inlet E for the heat transfer fluid FC, which is connected to the outlet point, a first outlet, which is connected to the mid-point and a second outlet, which is connected to an inlet point for the heat transfer fluid FC entering the fourth heat exchanger.

The first heat exchanger is preferably arranged upstream of the second heat exchanger according to a direction of circulation of the coolant FR inside the air conditioning loop.

The third heat exchanger advantageously comprises an inlet point for the heat transfer fluid FC, which is in fluidic communication with a discharge orifice for the heat transfer fluid FC leaving the first heat exchanger.

The system comprises in particular first means for maintaining a first flow rate of the heat transfer fluid FC, between the inlet point and the outlet point, at between 120 l/h and 300 l/h.

The first maintenance means include, for example, an arrangement with at least two passes of a first circulation channel of the heat transfer fluid FC inside the third heat exchanger.

The first maintenance means more specifically include an arrangement with at least four passes of said first circulation channel.

The first maintenance means include, for example, another restriction of circulation of the heat transfer fluid FC, in which the restriction is arranged upstream of the intake point.

The system preferably comprises second means for maintaining a second flow rate of the heat transfer fluid FC, between the intake point and a discharge point for the heat transfer fluid FC leaving the fourth heat exchanger, at between 40 l/h and 120 l/h.

The system advantageously includes a first channel housing the fourth heat exchanger and at least one first portion of the third heat exchanger.

The first channel preferably comprises an external air supply inlet in communication with the outside of the vehicle.

The system advantageously includes a second channel comprising a recycling air supply inlet in communication with the vehicle interior.

The second channel preferably houses a second portion of the third heat exchanger.

According to various alternatives, the second portion is indifferently separate from or integral with the first portion.

DESCRIPTION OF THE FIGURES

The present invention can be better understood in view of the following description of example embodiments, in reference to the appended figures, in which:

FIG. 1 is a partial diagrammatic drawing of system according to this invention.

FIG. 1bis is a detailed view of the system shown in FIG. 1.

FIG. 2 is a Mollier diagram partially showing a thermodynamic cycle to which a coolant FR, circulating inside an air conditioning loop in the system shown in FIG. 1, is subjected.

FIGS. 3 and 4 are diagrammatic views of respective alternative embodiments of the system shown in FIG. 1.

In FIG. 1, a motor vehicle is equipped with a heating, ventilation and/or air conditioning system 1 for modifying the aeraulic parameters of the air contained in the vehicle interior. The system 1 includes a housing 2 made of a plastic material for channeling an air flow 3 circulating between an air supply inlet 4 and an air discharge outlet 5 comprised by the housing 2.

To cool the air flow 3, the system 1 includes an air conditioning loop 6 inside of which a coolant FR circulates. This coolant is preferably carbon dioxide, known as R744. In a known manner, the air conditioning loop 6 comprises a compressor 7 for bringing the coolant FR to high pressure and high temperature. The air conditioning loop 6 also comprises a first fluid/fluid heat exchanger 8 and a second fluid/fluid heat exchanger 9, which are each intended to enable the coolant FR to transfer heat to a heat transfer fluid FC circulating inside a secondary loop 10. Inside the air conditioning loop 6, the coolant FR circulates from the compressor 7 to the first heat exchanger 8, then to the second heat exchanger 9 according to a direction of circulation 11 of the coolant FR inside the air conditioning loop 6. Inside the secondary loop 10, the heat transfer fluid FC circulates from the second heat exchanger 9 to the first heat exchanger 8 according to a direction of flow 12 of the heat transfer fluid FC inside the secondary loop 10.

The first heat exchanger 8 and the second heat exchanger 9 are each arranged so as to enable a direct exchange of heat between the heat transfer fluid FC and the coolant FR, without using an exchange of heat between the heat transfer fluid FC and the air and/or an exchange of heat between the coolant FR and the air.

The air conditioning loop 6 also includes an expansion member and an evaporator not shown in the figures. The evaporator is housed inside the housing 2 so as to enable the air flow 3 passing through it to cool. The air conditioning loop 6 preferably also comprises an internal heat exchanger and a coolant FR accumulator. The air conditioning loop 6 is capable of including other elements, such as valves for controlling the circulation of the coolant FR inside the air conditioning loop 6.

The secondary loop 10 comprises a pump 13 for circulating the heat transfer fluid FC, in which the pump is preferably arranged at the outlet of the first heat exchanger 8 according to the direction of flow 12 of the heat transfer fluid FC.

The secondary loop 10 comprises a third air heat exchanger 14 and a fourth air heat exchanger 15, which are arranged opposite one another inside the housing 2 of the system 1, so that the air flow 3 passes through them sequentially. The air heat exchangers 14, 15 are arranged so as to enable an exchange of heat between the heat transfer fluid FC and the air flow 3. The air heat exchangers 14, 15 therefore involve technology different from that of the fluid/fluid heat exchangers 8, 9 described above.

The third heat exchanger 14 comprises an air inlet face 16, which is placed opposite an air outlet face 17, comprised by the fourth heat exchanger 15. In other words, according to a direction of flow 18 of the air flow 3 inside the housing 2, the air flow 3 coming from the air supply inlet 4 passes through the third heat exchanger 15 and leaves the latter by means of the outlet face 17, so as to circulate inside the housing 2 toward the third heat exchanger 14. The air flow 3 then passes through the third heat exchanger 14 by penetrating the latter by means of the inlet face 16. The air inlet face 16 of the third heat exchanger 14 is preferably substantially parallel to the air outlet face 17 of the fourth heat exchanger 15. These arrangements are such that, due to the intake of the air flow 3 inside the housing 2, the air flow 3 is first heated by the fourth heat exchanger 15, then heated by the third heat exchanger 14, inside of which the heat transfer fluid FC is at a first temperature T1, which is greater than a temperature T2 of the heat transfer fluid FC inside the fourth heat exchanger 15.

The third heat exchanger 14 comprises an inlet point for heat transfer fluid FC entering the third heat exchanger 14. The inlet point 19 is in fluidic communication with a discharge orifice 20 for the heat transfer fluid FC leaving the first heat exchanger 8. According to the example shown, this fluidic communication is established by means of the pump 13.

The third heat exchanger 14 comprises an outlet point 21 for heat transfer fluid FC leaving the third heat exchanger 14, so that, inside the third heat exchanger 14, the heat transfer fluid FC flows inside a main circulation channel 30 provided between the inlet point 19 and the outlet point 21.

The outlet point 21 of the third heat exchanger 14 is in fluidic communication with means for bypass 22 of the heat transfer fluid FC either to a mid-point 26 of the secondary loop 10 or to an intake point 23 for heat transfer fluid FC entering the fourth heat exchanger 15. The mid-point 26 is interposed between the first heat exchanger 8 and the second heat exchanger 9.

More specifically, in FIG. 1bis, the bypass means 22 consist of a Y channel including an inlet E for heat transfer fluid FC, a first outlet S1 for heat transfer fluid FC and a second outlet S2 for heat transfer fluid FC. The inlet E is connected to the outlet point 21 of the third heat exchanger 14. The first outlet S1 is connected to the mid-point 26.

The second outlet S2 is connected to the intake point 23 of the fourth heat exchanger 15. The separation of the heat transfer fluid FC toward the first outlet S1 or toward the second outlet S2 is performed at a bypass point 22′. These arrangements are such that, at the outlet of the third heat exchanger 14, and more specifically at the bypass point 22′, the heat transfer fluid FC is either brought to the first heat exchanger 8 to be heated, or directed toward the fourth heat exchanger 15 in order to heat the air flow 3.

Inside the third heat exchanger 14, the heat transfer fluid FC circulates inside a secondary circulation channel 31, which extends from the intake point 23 toward a point of discharge 24 of the heat transfer fluid FC comprised by the third heat exchanger 14. The discharge point 24 of the third heat exchanger 14 is in communication with an inlet point 25 of the heat transfer fluid FC entering the second heat exchanger 9.

It results from these arrangements that the air flow 3 is capable of being heated in two stages, a first time when it is in contact with the main circulation channel and a second time when it is in contact with the secondary circulation channel 31. To optimize the exchange of heat between the heat transfer fluid FC and the air, the main circulation channel 30 comprises at least two passes, or even four or more passes. The number of passes of the main circulation channel 30 corresponds to the number of points of intersection between the main circulation channel 30 and the air flow 3 passing through the third heat exchanger 14. A restriction 42 is provided between the bypass point 22′ and the inlet point 23 so as to brake the passage of the heat transfer fluid and slow the flow rate thereof at the inlet of the fourth heat exchanger 15. Such a restriction 42 is, for example, provided in the form of a bottleneck, with a reduction in the diameter of a channel 43 connecting the bypass point 22′ and the inlet point 23 or the like.

The secondary loop 10 includes a main branch 29 that extends from the mid-point 26 to the bypass point 22′. The main branch 29 includes the first heat exchanger 8, the pump 13 and the main circulation channel 30. The main branch 29 comprises means for adjusting the flow rate of the heat transfer fluid FC between 120 l/h and 300 l/h.

At the bypass point 22′, the main branch 29 is divided into a first secondary branch 32 and a second secondary branch 33. The first secondary branch 32 connects the bypass point 22′ to the mid-point 26. The second secondary branch 33 includes the secondary circulation channel 31 and the second heat exchanger 9.

Inside the first secondary branch 32, the heat transfer fluid FC circulates at a flow rate of between 80 l/h and 180 l/h. These arrangements are designed to enable quick return of the heat transfer fluid FC to the first heat exchanger 8, for quick heating of the heat transfer fluid FC.

Inside the second secondary branch 33, the heat transfer fluid FC circulates at a flow rate of between 40 l/h and 120 l/h. These arrangements are designed to enable optimized heating of the air flow 3 in contact with the secondary circulation channel 31.

Finally, these arrangements result in a better compromise between quick heating of the heat transfer fluid FC, in particular inside the first heat exchanger 8, and quick cooling of the heat transfer fluid FC inside the third heat exchanger 14 and the fourth heat exchanger 15, for quick heating of the air flow 3.

All of these arrangements together are such that the exchange of heat between the coolant FR and the heat transfer fluid FC is optimized, while enabling a high “COP” to be obtained, for example between 3 and 4. In FIG. 2, which shows, in a Mollier diagram, a thermodynamic cycle to which the coolant FR is subjected inside the air conditioning loop 6, the isobaric cooling (AB) corresponds to the thermodynamic change to which the coolant FR is subjected first inside the first heat exchanger 8, then inside the second heat exchanger 9. The isobaric cooling (AB) is the sum of the first isobaric cooling (AC), which occurs inside the first heat exchanger 8 and the second isobaric cooling (CB), which occurs inside the second heat exchanger 9. At point A, namely at the inlet of the first heat exchanger 8, the coolant is at 110° C. At point B, namely between the outlet of the first heat exchanger 8 and the inlet of the second heat exchanger 9, the coolant is at 30° C. At point C, namely at the outlet of the second heat exchanger 9, the coolant is at 5° C. This result is achieved by the provisions of the present invention, on the basis of a reduction in the flow rate of the heat transfer fluid FC inside the second heat exchanger 9, in order to maximize the cooling of the coolant FR at the outlet of the second heat exchanger 9, i.e. at point B.

The provisions of the present invention enable such a high coefficient of performance to be obtained owing to a maximum reduction in the temperature of the coolant FR at the outlet of the second heat exchanger 9. The temperature of the coolant FR at the outlet of the second heat exchanger 9 is associated with the temperature of the heat transfer fluid FC at the inlet of the second heat exchanger 9, i.e. at the inlet point 25. The temperature of the heat transfer fluid FC at the inlet of the second heat exchanger 9 is limited by the temperature of the air flow 3 passing through the fourth heat exchanger 15. This invention enables the temperature of the coolant FR at the outlet of the second heat exchanger 9 to be reduced on the basis of a reduction in the flow rate of the heat transfer fluid FC inside the fourth heat exchanger 15.

The provisions of the present invention enable such a high coefficient of performance to be obtained also owing to the fact that the flow rate of the heat transfer fluid FC inside the third heat exchanger 14 is high, thereby enabling optimized heating of the air flow 3. This heating is possible in particular due to a high number of passes of the heat transfer fluid FC comprised by the main circulation channel 30, as well as a preheating of the heat transfer fluid FC by the fourth heat exchanger 15.

In FIGS. 3 and 4, the system 1 includes a first channel 35 and a second channel 39 forming the housing 2. The first channel 35 is equipped with an external air supply inlet 36 through which an external air flow 3a is admitted, coming from outside the vehicle. At the level of the external air supply inlet 36, the external air flow 3a has a temperature Tex, for example, on the order of −18° C. The second channel 39 is equipped with a recycling air supply inlet 40 through which a recycling air flow 3b is admitted, coming from the vehicle interior. At the level of the recycling air supply inlet 40, the recycling air flow 3b has a recycling temperature Tre, for example, on the order of 22° C. to 25° C.

The external air flow 3a circulates inside the first channel 35 so as to sequentially pass the fourth heat exchanger 15 and a first portion 37 of the third heat exchanger 14.

The recycling air flow 3b circulates inside the second channel 39 so as to pass through a second portion 38 of the fourth heat exchanger 15.

In FIG. 3, the second portion 38 of the first heat exchanger 14 is integral with the first portion 37 of the first heat exchanger 14.

In FIG. 4, the second portion 38 of the first heat exchanger 14 is separate from the first portion 37 of the first heat exchanger 14. The first portion 37 and the second portion 38 are placed in series, one with respect to the other, in which the second portion 38 is capable of being placed in a location of the vehicle where only recycling air passes through it, for example at the rear of the vehicle.

Claims

1. A heating, ventilation and/or air conditioning system (1) including an air conditioning loop (6) inside of which a coolant FR circulates, and a secondary loop (10) inside of which a heat transfer fluid FC circulates; said system (1) comprising a first heat exchanger (8) between the coolant FR and the heat transfer fluid FC, and a second heat exchanger (9) between the coolant FR and the heat transfer fluid FC; the secondary loop (10) includes a third heat exchanger (14) between the heat transfer fluid FC and the air, and a fourth heat exchanger (15) between the heat transfer fluid FC and the air, characterized in that the secondary loop (10) includes at least one bypass (22) of the heat transfer fluid FC from an outlet point (21) for the heat transfer fluid FC leaving the third heat exchanger (14) to an inlet point (23) for the heat transfer fluid FC entering the fourth heat exchanger (15).

2. A system (1) according to claim 1, characterized in that the outlet point (21) is connected to a mid-point (26) located on the secondary loop (10) between the first heat exchanger (8) and the second heat exchanger (9).

3. A system (1) according to claim 2, characterized in that the bypass (22) comprises a “Y” channel, including an inlet E for the heat transfer fluid FC, which is connected to the outlet point (21), a first outlet S1, which is connected to the mid-point (26) and a second outlet S2, which is connected to an inlet point (23) for the heat transfer fluid FC entering the fourth heat exchanger (15).

4. A system (1) according to claim 1, characterized in that the first heat exchanger (8) is arranged upstream of the second heat exchanger (9) according to a direction of circulation (11) of the coolant FR inside the air conditioning loop (6).

5. A system (1) according to claim 1, characterized in that the third heat exchanger (14) comprises an inlet point (19) for the heat transfer fluid FC, which is in fluidic communication with a discharge orifice (20) for the heat transfer fluid FC leaving the first heat exchanger (8).

6. A system (1) according to claim 5, further comprising first means for maintaining a first flow rate of the heat transfer fluid FC, between the inlet point (19) and the outlet point (21), at between 120 l/h and 300 l/h.

7. A system (1) according to claim 6, characterized in that the first maintenance means include an arrangement with at least two passes of a first circulation channel (30) of the heat transfer fluid FC inside the third heat exchanger (14).

8. A system (1) according to claim 7, characterized in that the first maintenance means include an arrangement with at least four passes of the first circulation channel (30).

9. A system (1) according to claim 6, characterized in that the first maintenance means include a restriction (42) of circulation of the heat transfer fluid FC, in which the restriction (42) is arranged upstream of the intake point (23).

10. A system (1) according to claim 3, further comprising second means for maintaining a second flow rate of the heat transfer fluid FC, between the intake point (23) and a discharge point (24) for the heat transfer fluid FC leaving the fourth heat exchanger (15), at between 40 l/h and 120 l/h.

11. A system (1) according to claim 1, further comprising a first channel (35) housing the fourth heat exchanger (15) and at least one first portion (37) of the third heat exchanger (14).

12. A system (1) according to claim 11, characterized in that the first channel comprises an external air supply inlet (36) in communication with the outside of a vehicle.

13. A system (1) according to claim 11, further comprising a second channel (39) comprising a recycling air supply inlet (43) in communication with a vehicle interior.

14. A system (1) according to 13, characterized in that the second channel (39) houses a second portion (38) of the third heat exchanger (14).

15. A system (1) according to claim 14, characterized in that the second portion (38) is indifferently separate from or integral with the first portion (37).