TRANSCRITICAL AIR CONDITIONING CIRCUIT WITH INTEGRATED EXPANSION VESSEL

Description

FIELD OF THE INVENTION

[0001] The present invention relates to the field of air conditioning and more particularly to air conditioning circuits with transcritical operation. BACKGROUND OF THE INVENTION

[0002] Vehicle cabin air conditioning systems are widely used, regardless of the vehicle's engine type. Typically, an air conditioning system operates on a subcritical vapor compression cycle using a fluid such as that produced under the reference R134a (1,1,1,2-tetrafluoroethane). A thermodynamic cycle is said to be subcritical when it operates below the fluid's critical temperature. The critical temperature of a fluid is its maximum temperature in the liquid phase, regardless of pressure, i.e., the temperature of its critical point.

[0003] The use of fluids such as R134a will soon be banned due to its significant greenhouse effect. Among the alternatives, carbon dioxide (CO 2 ), also known as R744, seems to be the most promising replacement for future air conditioning circuits. However, due to the low critical temperature (31 degrees Celsius) of CO 2 , an air conditioning circuit using CO 2 must adopt a transcritical operating cycle, i.e., involving temperatures / pressures higher than the critical temperature / pressure of the fluid. The equipment normally used for circuits with a subcritical operating cycle is not suitable for transcritical operating cycles and must therefore be redesigned.

[0004] Conventionally, a transcritical operating cycle air conditioning system comprises a rotary compressor driven, via a clutch, by a rotating element of the vehicle's engine. With reference to the figure 1 , this compressor 60 compresses a refrigerant fluid and directs it to a gas cooler 61 attached to a fan. The fan forces an air flow through the gas cooler 61 in order to evacuate a maximum of calories from the compressed fluid. The refrigerant fluid is then directed to the cold circuit of an internal exchanger 62 in which the refrigerant fluid still gives up its heat to a portion of the circuit corresponding to the hot circuit of the internal exchanger 62. The refrigerant fluid thus cooled is then directed to an expansion valve 63 which expands the refrigerant fluid and directs it to a “chiller” type exchanger (or water cooler in French) 64. The “chiller” type exchanger 64 is linked to a cooling circuit 65 in which a cooling fluid circulates in heat exchange with the refrigerant fluid._The cooling circuit also includes an expansion tank whose function is to provide an expansion volume absorbing variations in the volume of the cooling fluid.

[0005] The prior art solutions are disclosed in documents [WO 2007 / 088012 A1], [US 2012 / 151950 A1] and [US 2007 / 056720 A1].

[0006] As car manufacturers want to offer compact and as inexpensive vehicles as possible, there is a need for compact and economical transcritical duty cycle air conditioning systems. SUBJECT OF THE INVENTION

[0007] One aim of the invention is to reduce the size and manufacturing and assembly costs of an air conditioning circuit with a transcritical operating cycle. SUMMARY OF THE INVENTION

[0008] For this purpose, an air conditioning device with a transcritical operating cycle is provided, comprising a circuit conveying a refrigerant fluid and successively connecting: the outlet of a compressor; a gas cooler; the cold circuit of an intercooler; an expansion valve; a second exchanger of the air conditioning device having a circulation volume of a refrigerant fluid in heat exchange with the refrigerant fluid; the inlet of the hot circuit of the intercooler. The outlet of the hot circuit of the intercooler is connected to the inlet of the compressor.

[0009] According to the invention, the second exchanger comprises an expansion volume for the cooling fluid.

[0010] This reduces the size of the second exchanger and expansion tank assembly by merging these two components. The risk of fluid leakage is also reduced by reducing the number of pipes. Finally, manufacturing and assembly operations are simplified, resulting in a more reliable, more compact and less expensive device than previous solutions.

[0011] The invention also comprises a second exchanger for a transcritical air conditioning circuit, comprising a bundle of tubes for circulating a refrigerant fluid which extend into a circulation volume of a refrigerant fluid. The second exchanger comprises an expansion volume for the refrigerant fluid.

[0012] The circulation volume of the cooling fluid of such an exchanger is advantageously of substantially parallelepipedal shape and is delimited by a body comprising a first molded element and a second element attached by stapling to the first. This method of assembly is particularly economical and reliable.

[0013] According to a particular embodiment, the first element has a substantially parallelepiped shape and the second element is substantially planar.

[0014] Alternatively, the first element and the second element are both substantially parallelepipedal in shape.

[0015] Thus, it is possible to offer exchangers, for transcritical air conditioning circuits, having two different refrigerant circulation volumes and having a significant number of parts in common, which contributes to reducing the unit price of each exchanger.

[0016] Finally, at least one of the elements comprises at least one groove for receiving the sides of a collector of the bundle of tubes for circulating the refrigerant fluid.

[0017] This makes it easier to position the various components of the second exchanger relative to each other during assembly and thus reduces its manufacturing cost.

[0018] Other characteristics and advantages will emerge upon reading the following description of non-limiting embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Reference will be made to the attached drawings, including: there figure 1 is a schematic representation of a prior art transcritical air conditioning circuit; figure 2 is a schematic representation of a transcritical air conditioning circuit according to the invention; figure 3 is a perspective view of a first embodiment of a second exchanger according to the invention; the figure 4 is a perspective view of the interchange of the figure 3 after a 90° rotation; the figure 5 is an exploded perspective view of the interchange of the figure 4 ; there figure 6 is a section along a VI-VI plan of the interchange of the figure 4 ; there figure 7 is a perspective view of a second embodiment of a second exchanger according to the invention; figure 8 is a perspective view of the interchange of the figure 7 after a 90° rotation; the figure 9 is an exploded perspective view of the interchange of the figure 8 . DETAILED DESCRIPTION OF THE INVENTION

[0020] In reference to the figure 2 , the transcritical operating cycle air conditioning device, generally designated 1, is mounted in an engine compartment 2 of a vehicle 3 with an internal combustion engine (not shown).

[0021] The device 1 comprises a circuit 4 conveying a refrigerant fluid 5, here CO 2 , in a direction represented by the arrows. The circuit 4 successively connects: the outlet 6 of a compressor 7; a gas cooler 8; the cold circuit 9 of an intercooler 10; an expansion valve 11; a second exchanger 12 of the air conditioning device; and the inlet 13 of the hot circuit 14 of the intercooler 10.

[0022] The outlet 15 of the hot circuit 14 of the intercooler 10 is connected to the inlet 16 of the compressor 7.

[0023] A cooling circuit 20 conveys a cooling fluid 21, here glycolated water, by means of a circulation pump 22. The circuit 20 comprises a fluid / air heat exchanger 23 through which a fan 24 forces a flow of air intended for the passenger compartment of the vehicle 3. The cooling fluid 21 enters the second exchanger 12 in order to lose calories absorbed by the change of state of the refrigerant fluid 5 in the second exchanger 12.

[0024] The second exchanger 12 may be used as a "chiller" type exchanger or water cooler in French. In such use, this type of exchanger functions as an exchanger capable of creating cold for an exchange with a cooling fluid of another circuit of the motor vehicle, in particular when the latter includes batteries.

[0025] The second heat exchanger can also be used as a condenser type exchanger or as a gas cooler type exchanger cooled with a cooling fluid (such as glycol water).

[0026] A first embodiment of the second exchanger 12 will now be described with reference to the figures 3 à 5 .

[0027] The second exchanger 12 comprises a body 30 of substantially parallelepipedal shape delimiting an interior volume 31 containing a tube bundle 50. The body 30 comprises a first molded element 32 of substantially parallelepipedal shape on which is attached a second substantially planar element 33. The elements 32 and 33 are secured to each other by a plurality of clips 34 integrated into the second element 33. The first element 32 has an open face 35 and is provided with a plurality of external ribs 36 reinforcing its resistance to pressure. The first element 32 comprises a first internal peripheral groove 37 and a second identical groove 38. The grooves 37 and 38 are respectively located at the upper end 39 and at the lower end 40 of the first element 32.The first element 32 also comprises a first and a second tubular connector 41 and 42 opening respectively into an upper and lower portion of the internal volume 31. As visible in the figures, the connectors 41 and 42 project from two opposite faces of the first element 32, one near the upper end 39 and the other near the lower end 40. A portion 43 of substantially parallelepipedal shape is connected by its base to the upper end 39 of the first element 32. The portion 43 is in fluid connection with the volume 31 because its base is hollowed out. A plug 44 located on the face opposite the base of the portion 43 allows access to the internal volume 43.1 of the portion 43.

[0028] The second element 33 comprises a first tubular connection 45 and a second tubular connection 46 opening into the volume 31 respectively facing the grooves 37 and 38.

[0029] The tubular bundle 50 comprises, here, seven tubes 51 parallel to each other and of rectangular section. The tubes 51 comprise notches 51.1 which increase the exchange surface of the tubes with the medium in which they extend. The tubes 51 extend in the volume 31 from an inlet manifold 52 to an outlet manifold 53. Each manifold 52 and 53 has a substantially parallelepiped shape and has respectively a sealing element 54 and 55 which respectively fit into the tubular part of the connectors 46 and 45.

[0030] During the manufacture of the second exchanger 12, the sides of the collectors 53 and 54 of the tube bundle 50 are respectively placed in the grooves 38 and 37 of the first element 32. The second element 33 is then presented so that the sealing elements 54 and 55 engage respectively in the tubular parts of the connectors 46 and 45. The second element 33 is then brought into contact with the first element 32 and the elements 32 and 33 are secured using the clips 34. The second exchanger 12 thus formed therefore comprises a tube bundle 50 extending in an interior volume 31 between the two collectors 52 and 53. The second exchanger 12 also comprises the internal volume 43.1 of the portion 43 in fluid connection with the volume 31.

[0031] The second exchanger 12 is connected to the air conditioning device 1 so that the refrigerant 5 at the outlet of the expansion valve 11 enters the inlet manifold 52 via the connection 46 and leaves the outlet manifold 53 via the connection 45. The inlet of the exchanger 23 is connected to the connection 42 and the outlet of the exchanger 23 is connected to the connection 41. In operation, the expanded refrigerant 5 evaporates in the tubes 51 of the tube bundle 50 and cools the cooling fluid 21 circulating in the interior volume 31 under the effect of the circulation pump 22. In the event of a variation in the volume of cooling fluid 21 caused by a change in ambient pressure or significant heat to be evacuated, the volume 43.1 allows the expansion of the cooling fluid 21. Indeed, the volume 43.1 being located above the connection 41 of the cooling fluid outlet 21, the latter is little or not occupied by the cooling fluid 21 and forms an expansion volume of the latter.

[0032] Elements identical or analogous to those previously described will bear a numerical reference identical to these in the following description of a second embodiment of the invention with reference to figures 7 à 9 .

[0033] The body 30 of the second exchanger 12 is of substantially parallelepipedal shape and comprises a first molded element 32 of substantially parallelepipedal shape, open on one of its faces. A second element 70, also substantially parallelepipedal, comprises an open face on which the open face of the element 32 is attached. The bodies 32 and 70 thus define an internal volume 71 for circulation of the cooling fluid 21. The elements 32 and 70 are secured to each other by a plurality of clips 34. The connection between the two elements 32 and 70 can be achieved by clips, screws, or by induction welding or by vibration. The second element 70 is provided with a plurality of external ribs 36 reinforcing its resistance to pressure; as well as a first internal peripheral groove 72 and a second internal peripheral groove 73 identical to the groove 72.The grooves 72 and 73 are respectively located at the upper end 74 and at the lower end 75 of the second element 70. The second element 70 comprises a first tubular connection 45 and a second tubular connection 46 opening into the volume 71 respectively facing the grooves 72 and 73.

[0034] The tube bundle 80 comprises, here, fourteen tubes 51 extending in the volume 71 from the inlet manifold 52 to the outlet manifold 53.

[0035] During the manufacture of the second exchanger 12, the sides of the collectors 53 and 54 of the tube bundle 80 are respectively placed in the grooves 38 and 37 of the first element 32. The second element 70 is then presented so that the grooves 73 and 72 face the sides of the collectors 53 and 54. In this position, the sealing elements 54 and 55 engage respectively in the tubular parts of the connectors 46 and 45. The second element 70 is then brought into contact with the first element 32 and the elements are secured by stapling. The second exchanger 12 thus formed therefore comprises a tube bundle 80 providing an exchange surface of fourteen tubes 51. The manufacture of the second exchanger according to this second embodiment uses a significant proportion of elements common or identical with the first embodiment, resulting in reduced manufacturing and tooling costs.

[0036] Of course, the invention is not limited to the embodiments described but encompasses all the variants falling within the scope of the invention as defined by the claims.

[0037] Especially : although here the circuit directly connects the different components of the air conditioning device, the invention also applies to components connected to each other via other components such as for example a desiccator, control or regulation members, valves or others; although here the refrigerant fluid is CO 2 , the invention also applies to other types of refrigerant fluids suitable for operation in a transcritical cycle; although here the cooling fluid is glycolated water, the invention also applies to other types of refrigerant fluids such as for example alcohol, salt water, ammonia or ammonium chloride; although here the elements constituting the body of the second exchanger are made by molding, the invention also applies to other embodiments of the elements such as for example stamping, forming, mechanical welding or machining;although here the elements of the body are connected to each other by stapling, the invention also applies to elements connected to each other by other assembly means such as welding, screwing, gluing; although here the connections attached to the body of the second exchanger are tubular, the invention also applies to other types of connections such as bayonet connections or cartridge-type connections; although here the tubes of the tube bundle are crenellated and number seven or fourteen, the invention also applies to tubes of any shape in different numbers, such as smooth tubes.;

Claims

1. Air conditioning device (1) of an engine compartment (2) of a vehicle (3) with an engine, the device (1) with a transcritical operating cycle, the device comprising a circuit (4) conveying a refrigerant (5) and successively connecting - the outlet (6) of a compressor (7); - a gas cooler (8); - the cold circuit (9) of an intermediate cooler (10); - an expansion valve (11); - a second exchanger (12) having a volume (31, 71) for circulation of a coolant (21) in heat exchange with the refrigerant (5); - the inlet (13) of the hot circuit (14) of the intermediate cooler (10), the outlet (15) of the hot circuit (14) of the intermediate cooler (10) being connected to the inlet (16) of the compressor (7), the air conditioning device (1) being characterized in that the second exchanger (12) comprises a volume (43.1) for expansion of the coolant (21), said exchanger (12) comprising a body (30) of substantially parallelepipedal shape delimiting an interior volume (31) containing a tubular bundle (50), the body (30) comprises a first moulded element (32) of substantially parallelepipedal shape to which is attached a substantially planar second element (33), wherein the first element (32) comprises a first internal peripheral groove (37) and an identical second groove (38), wherein the grooves (37) and (38) are respectively situated at the upper end (39) and at the lower end (40) of the first element (32), wherein the second element (33) comprises a first tubular connector (45) and a second tubular connector (46) leading into the volume (31) respectively facing the grooves (37, 38), wherein the flanks of the manifolds (53) and (54) of the tubular bundle (50) are respectively placed in the grooves (38) and (37) of the first element (32).

2. Device (1) according to Claim 1, wherein the expansion volume (43.1) of the second exchanger (12) also comprises an access plug (44).

3. Exchanger (12) for an air conditioning device (1) with transcritical operation, comprising a bundle (50) of tubes (51) for circulation of a refrigerant (5) that extend in a volume (31, 71) for circulation of a coolant (21), said exchanger (12) comprising a volume (43.1) for expansion of the coolant (21), said exchanger (12) comprising a body (30) of substantially parallelepipedal shape delimiting an interior volume (31) containing a tubular bundle (50), the body (30) comprises a first moulded element (32) of substantially parallelepipedal shape to which is attached a substantially planar second element (33), wherein the second element (33) comprises a first tubular connector (45) and a second tubular connector (46) leading into the volume (31) respectively facing the grooves (37, 38), wherein the flanks of the manifolds (53) and (54) of the tubular bundle (50) are respectively placed in the grooves (38) and (37) of the first element (32).

4. Exchanger (12) according to Claim 3, comprising a plug (44) for access to the volume (43.1) for expansion of the coolant (21).

5. Exchanger (12) according to Claim 3, wherein the volume (31, 71) for circulation of the coolant (21) is of substantially parallelepipedal shape and is delimited by a body (30) comprising a first element (32) and a second element (33, 70) attached by clipping to the first element (32).

6. Exchanger (12) according to Claim 5, wherein the first element (32) and the second element (70) are of substantially parallelepipedal shape.

7. Exchanger (12) according to Claim 5, wherein at least one of the elements (32, 70) comprises at least one groove (37, 38, 72, 73) for receiving the flanks of a manifold (52, 53) of the bundle (50) of tubes (51) for circulation of the refrigerant (5).