FR2906357A1 - LIQUID / GAS TYPE HEAT EXCHANGER, IN PARTICULAR FOR A MOTOR VEHICLE AIR CONDITIONING EQUIPMENT USING A SUPERCRITICAL OPERATING REFRIGERANT FLUID SUCH AS CO2 - Google Patents

Abstract

The exchanger (WGC2; WGC3) comprises at least two adjacent coolers (30, 40; 30 ', 40'), each having a bundle (34) of elongate multichannel tubes traversed by the refrigerant gas, joined by collector boxes. end (36, 38) connected to a refrigerant gas circuit of the air conditioning equipment. A housing (50) encloses the tube bundle and forms an interior space with an inlet and a coolant outlet to allow it to flow between the tubes of the bundle. The two casings have a common wall (52) having at least one orifice (60) for placing the two inner volumes in communication. It is thus possible to produce a compact gas cooler incorporating in the same block two water / gas exchange stages (WGC2, WGC3), as well as possibly an internal gas / gas exchanger of the air conditioning circuit.

Description

1 Liquid / gas heat exchanger, especially for equipment

  The invention relates to liquid / gas-type heat exchangers, in particular for air-conditioning equipment for a motor vehicle. It relates more particularly (but without limitation) heat exchangers for air conditioning circuits using a refrigerant such as carbon dioxide (CO2) operating in the supercritical state, that is to say where the fluid remains most of the time in the gaseous state in the air conditioning circuit. Such a circuit essentially comprises a compressor, a gas cooler, an internal heat exchanger, a pressure reducer, an evaporator and an accumulator. The gas cooler, which replaces the condenser of conventional air conditioning circuits, is arranged to cool the gaseous refrigerant by heat exchange with either the ambient air (air / gas type heat exchanger) or engine cooling (liquid / gas heat exchanger). The invention relates more precisely to the liquid / gas type heat exchangers, also called "water / gas exchanger" or Water / Gas Cooler ("WGC"), equipping such circuits. Such an exchanger is described in particular in the publication FR-A-2 852 383 (Valeo Motor Thermal). Due to the high temperatures reached by the refrigerant gas, which can reach 80 to 100 C in the case of CO2, as well as the large temperature difference encountered in the gas cooler (in the case of CO2, 5 it can be cooled to temperatures as low as 30 to 60 ° C), the cooling of the gas is generally operated on several stages, with each a specific liquid / gas heat exchanger.

  Publication FR-A-2 875 743 (Valeo Thermal Systems) thus describes an air-conditioning circuit in which a gaseous refrigerant such as CO2 is cooled by a succession of three exchangers operating respectively at high temperature (80 to 100 ° C., typically 90 ° C. ), low temperature (50 to 70 C, typically 60 C) and very low temperature (30 to 60 C, typically 50 C). These three heat exchangers are supplied with heat transfer liquid by different fluid circulation loops, with specific temperatures and flow rates at each stage of the gas cooler. The use of several exchangers for cooling the gas significantly improves the efficiency of the heat exchange, but on the other hand induces an increase in the size of the gas cooler, which complicates its implementation in the vehicles, given the multiplicity of architectures of engines and their cooling and air conditioning systems.

  Furthermore, air conditioning circuits using CO2 as a cooling fluid are more complex to achieve, especially in terms of mechanical strength, given the fluid pressures that can reach values up to 450 bar, much higher than the pressures usually encountered in conventional air conditioning systems using phase change fluids such as fluorinated compounds. These pressure constraints impose particular mechanical and technological solutions, to meet the very strict requirements of reliability and tightness. The problem that the invention aims to solve is that of reducing the size of the liquid / gas heat exchanger, to make it easier to install the gas cooler under the hood of the vehicle in a maximum of architectures. which may be encountered, in particular to bring the gas cooler closer to the compressor or the evaporator, and to reduce the lengths of gas pipes. The object of the invention is also to make it possible to fix the exchanger on the engine or on the compressor, a configuration which has the particular advantage of allowing the use of rigid tubes in the most heat-treated zone. , between compressor and gas cooler.

Another object of the invention is to allow the integration in the same functional block not only of the liquid / gas heat exchanger ("WGC") cooling the gas output compressor, but also the internal gas / gas heat exchanger of the cooling circuit. This internal heat exchanger, also known as "IHX" (Interchange Heat eXchanger) is in fact arranged in the circulation loop of the refrigerant gas just downstream of the cooler WGC (hot circuit) and upstream of the compressor 2906357 4 (cold circuit ), so that it would be advantageous to mechanically and functionally combine the gas cooler WGC and the internal heat exchanger IHX so as to eliminate the lengths of connections between the exchangers and to minimize the length of connection to the compressor. Yet another object of the invention is to provide a liquid / gas heat exchanger which is, in practice, as compact and provides the same performance as an air / heat exchanger. gas. The liquid / gas exchangers proposed up to now were indeed, at equal performance, generally more bulky than an air / gas exchanger, which made them prefer despite their disadvantages, in particular the need for 15 long lengths of gas tubes. high pressure to connect to the rest of the circuit the air / gas exchanger mounted on the front of the vehicle (to allow satisfactory cooling). In the case of rigid tubes, these connections are expensive and difficult to decouple from the engine; in the case of flexible connectors, these are very thermally and mechanically stressed. In contrast, a liquid / gas type exchanger does not need to be mounted on the front face and can therefore be fastened close to the engine or the compressor, with rigid pipes in the most stressed zones. thermally and mechanically. The invention proposes a heat exchanger between a first fluid and a second fluid of the known type described in FR-A-2 852 383 mentioned above, that is to say comprising an interior space and a tube bundle. provided in said interior space, wherein the first fluid flows and is cooled by the second fluid, and wherein the second fluid is introduced into the heat exchanger through an inlet manifold and discharged through an outlet manifold. and occupies the interior space of the exchanger ("internal space of the exchanger" is understood to mean the space between, on the one hand, the tubes serving to convey the first fluid and, on the other hand, the outer walls or the heat exchanger shell).

According to a first aspect of the invention, it relates to such a heat exchanger considered as such, which does not intrinsically include the collector box (s) conventionally serving as an inlet and outlet chamber for one of the fluids.

In a characteristic manner of the invention, the heat exchanger defines at least two passes for the second fluid ("pass" means the path of a fluid in one direction).

Thus, with two passes the fluid circulates within the heat exchanger (which generally extends in one plane) in two directions and along two distinct paths, these two directions of circulation being usually - but not necessarily - opposed. to one another. In the example of three passes, the fluid flows in the plane defined by the exchanger with two directions of circulation and three paths. In other words, the number of passes is related to the number of changes in fluid flow direction. Thus, a two-pass fluid has a change of direction while a three-pass fluid has two changes in direction of flow.

The heat exchanger can further define at least two passes also for the first fluid. When the first fluid is a gas and the second fluid is a liquid, a liquid / gas heat exchanger ("WGC") is available which overcomes the disadvantages of the prior art by separating the liquid flow into two different circuits. each fed with a temperature-matched heat sink source with one or more countercurrent passes over the gas. It thus becomes possible to produce a very compact heat exchanger, of substantially parallelepipedal shape, and of performances comparable to those of an air / gas type exchanger.

In a particular embodiment, the interior space comprises at least two housings, each of the housings enclosing a plurality of tubes and delimiting a passage for the first fluid ("housing" means an outer envelope for the heat exchanger, the walls of this envelope may be formed in part by one or collector box walls (s) attached (s) to the heat exchanger).

In the latter case, the two housings may have a common wall, in particular parallel to the tube bundle, which comprises at least one orifice for placing the inner space of the two housings in communication.

Furthermore, the heat exchanger may comprise collecting boxes, disposed at the ends of the bundle, capable of assembling and placing the tubes of the bundle in communication at their ends, these manifolds being able to be otherwise connected to a circulation circuit of the first fluid. In the latter case, and according to a second aspect of the invention, it also relates to a heat exchange module comprising at least two adjacent heat exchangers as defined above according to the first aspect of the invention. invention, with a first heat exchanger and a second heat exchanger. One of the heat exchangers 10 is connected to an inlet pipe and the other heat exchanger is connected to an outlet pipe, these two pipes being able to be placed in communication with a circuit of the second fluid. The two heat exchangers have a common wall extending parallel to the tube bundle and having at least one port for communicating the interior space of the first heat exchanger with the interior space of the second heat exchanger. In a preferred embodiment, the fluid inlet and outlet manifolds are disposed at the same respective end of the first heat exchanger and the second heat exchanger, the port (s) being placed ( s) in the region of the opposite end of the first heat exchanger and the second heat exchanger. Very advantageously, each heat exchanger comprises a casing with two opposite side walls between which the bundle of tubes extends transversely, and in that the transverse dimension separating these walls is substantially the same as that of the bundle. of tubes, with the exception of enlarged lateral regions located in the vicinity of the tubing and of the port (s) of communication. The side walls and the bundle of tubes may then be: brazed together in the region where the transverse dimension separating these walls is substantially the same as that of the bundle of tubes. In a preferred embodiment, the collector boxes are formed of a superposition of plates alternately forming fluid passage and spacer for the selective distribution of the first fluid in the various tubes of the bundle, and the wall common to both exchangers comprises longitudinal extension extending into the superposition of plates constituting the manifolds, this extension forming a partition for the circulation of the first fluid in the manifolds located on either side of this partition.

In a dual heat exchanger configuration, said at least two adjacent heat exchanger modules are two main heat exchangers forming a first heat exchanger stage, and at least two adjoining auxiliary heat exchangers forming a second heat exchanger stage are provided, distinct from the first stage exchanger and mounted adjacent thereto. The collector boxes of the first and second exchanger stages are interconnected successively in series so as to allow the circulation of the first fluid successively in the first and the second exchanger stage.

In this case, advantageously: the module comprises a wall common to the two exchanger stages, devoid of a communication opening port 5 of the respective interior volumes of the heat exchanger casings located on either side of this common wall. ; the module comprises between the two heat exchangers a spacer element interposed so as to define an interval between the heat exchangers vis-à-vis the first exchanger stage and the second exchanger stage; the outlet pipe of the first exchanger stage is connected to the inlet pipe of the second exchanger stage so as to allow the circulation of the second fluid successively in the first and then the second exchanger stage. In a particularly advantageous embodiment, the device of the invention further includes an internal heat exchanger stage. This comprises a stack of elongate multichannel tubes, these tubes being contiguous and stacked alternately in two series of nested tubes, with a first series of tubes connected to the outlet of the heat exchanger (s). heat so as to be run-through by the first high pressure fluid delivered by this (these) heat exchanger (s), and a second series of tubes adapted to be connected to a low pressure branch of the first fluid circuit so to be traversed by 30 the first cold fluid circulating in this branch.

The internal heat exchanger stage may advantageously be contiguous to the assembly formed by the first and second heat exchanger stages.

This internal exchanger stage can in particular comprise collecting boxes arranged at the opposite ends of the stack of tubes, able to join and connect at their ends the respective tubes of the two series of tubes and to selectively distribute the first fluid therein, these collector boxes further comprising means for connecting the circuit of the first fluid. These manifolds are preferably arranged in alignment with the heat exchanger boxes of heat exchangers of the first and second heat exchanger stages. They can also be connected in series with the collector boxes of the heat exchangers of the first and second heat exchanger stages so as to allow the supply of the internal exchanger stage by the hot fluid at high pressure delivered directly by the heat exchangers. first and second stages heat exchangers. According to a third aspect of the invention, it relates to an air conditioning equipment for a motor vehicle comprising a heat exchanger, or a heat exchange module, as defined above. An embodiment of the device of the invention will now be described with reference to the appended drawings in which the same reference numerals designate elements that are identical or functionally similar from one figure to another.

FIG. 1 is a diagram showing the various elements of a motor vehicle air-conditioning circuit using a refrigerant fluid operating in the supercritical state such as CO 2. Figure 2 is a perspective view of a double liquid / gas heat exchanger according to the invention.

FIG. 3 is a front view of the exchanger of FIG. 2, illustrating in particular the flow directions of the gas and liquid circuits. FIG. 4 is an exploded perspective view of the exchanger 15 of FIG. 2. FIG. 5 is a sectional side view, along VV of FIG. 3, at the level of the communication passages of the water circuits of FIGS. different modules. Figure 6 is a perspective view of a double liquid / gas heat exchanger of the type illustrated in Figure 2, further associated with an internal heat exchanger disposed in the same functional unit.

FIG. 7 is an exploded perspective view of the internal heat exchanger of the assembly of FIG. 6. FIG. 8 is a cross-sectional plan view of the heat exchanger at the elevated warm circuit. pressure. Figure 9 is a plan view, in section, of the heat exchanger at the low pressure cold circuit.

FIG. 1 illustrates a motor vehicle air-conditioning circuit using a refrigerant fluid operating in the supercritical state such as CO2, where the temperature of the coolant is lowered by heat exchange with the engine coolant. . The circuit comprises a compressor 10, for example an externally controlled compressor controlled by a control electronics 12. Compressed refrigerant gas G then passes through a gas cooler 14 comprising one or more successive exchangers, namely three exchangers WGC1, WGC2 and WGC3 mounted in series in the example shown. At the outlet of the cooler 14, the refrigerant gas G passes through an internal exchanger IHX referenced 16, then is expanded in a pressure reducer 18, for example an expansion valve controlled also by the control electronics 12. The gas thus expanded is conducted to an exchanger 20 providing the same function as the evaporator of a conventional refrigerant phase change circuit, then to an accumulator 22 and the internal exchanger 16, before being recycled to the compressor 10. The gas cooler 14 comprises, for example, as illustrated in FIG. 1, a series of three exchangers WGC1, WGC2 and WGC3 operating respectively at high temperature, low temperature and very low temperature. The first heat exchanger WGC1 is a water / gas heat exchanger using as coolant the engine coolant, which here constitutes the heat transfer liquid L flowing in the water-side exchanger. This liquid is usually water with an antifreeze (brine) or similar liquid. The low temperature heat exchanger WGC2 also uses as coolant source the engine coolant L, via a separate loop of the loop feeding the exchanger WGC1. The very low temperature heat exchanger WGC3 5 can also use as coolant the coolant of the engine L, via a separate loop of the loop feeding the heat exchanger WGC1, or operate by contact with ambient air taken outside. of the vehicle. In simplified embodiments, the third stage WGC3 of the cooler can be omitted, the coolant then simply being cooled by two exchangers both traversed by the engine coolant.

The high temperature is usually of the order of 80 to 100 C (typically 90 C), the low temperature of the order of the order 50 to 70 C (typically 60 C), and the very low temperature of the 30 to 60 ° C. (typically 50 ° C.) in the case of a water / gas exchanger using the engine coolant, or a temperature depending on the ambient air in the case of an air / gas exchanger (the temperature "being understood as the temperature of the heat-carrier liquid circulating in the water / gas exchanger).

The invention relates more particularly to the mechanical production of low temperature exchangers WGC2 and / or very low temperature WGC3. Next, a particularly advantageous embodiment will be described in which the two exchangers WGC2 and WGC3 are combined in one and the same block, but this embodiment is not limiting and the invention is also applicable to the isolated embodiment of FIG. one of the exchangers WGC2 or WGC3, 2906357 14 or to the realization of another exchanger of the liquid / gas type. Furthermore, the exchanger block of the invention can also be integrated into an assembly comprising other members of the circuit of the air conditioning equipment. It can in particular be grouped with the internal heat exchanger 16, insofar as it is mounted directly downstream of the exchangers WGC2 and WGC3 in the air conditioning circuit. This last variant embodiment will be described in more detail with reference to FIGS. 6 to 9.

In FIG. 2, the reference 24 generally denotes a unitary unit grouping together the two exchangers WGC2 and WGC3 operating respectively at low and very low temperatures.

This unit block 24 comprises a gas inlet 26 receiving the refrigerant gas G after it has been cooled by the very high temperature exchanger WGC1, and a gas outlet 28 delivering the gas cooled by the exchangers WGC2 and WGC3 to the internal exchanger 16 for expansion and recycling 25 to the compressor. The low temperature heat exchanger WGC2 consists of two superposed cooler modules 30, 40, of similar external dimensions. The upper module 30 is provided with a pipe 32 for the outlet of the heat-transfer liquid L, and the lower module 40 for a pipe 42 for the admission of the coolant L.

The very low temperature heat exchanger WGC3 consists of two superposed cooler modules 30 ', 40', of external dimensions similar to each other and similar to those of the modules 30 and 40. The upper module 30 'is provided with a tube 32 'for the outlet of the coolant L, and the lower module 40' for a tube 42 'for the admission of the coolant L. As illustrated in FIGS. 3 to 5, each of the modules 10 comprises a bundle of flat elongated multichannel tubes traversed by the refrigerant gas. The upper module 30 of the exchanger WGC2 thus includes a beam referenced 34, and the lower module 40, a beam referenced 44. The modules 30 'and 40' of the exchanger WGC2 have an identical structure. The tubes of the bundles 34, 44 are of the multichannel type, pierced internally by a multiplicity of parallel channels traversed by the refrigerant gas under pressure. The various multichannel tubes of the bundle extend parallel to each other in the longitudinal direction (i.e. the direction of the largest dimension of the modules 30, 40) and are spaced apart from each other so as to allow the circulation of the coolant between the tubes, and therefore on each of the faces of the flat tubes internally traversed by the gas to be cooled. The different tubes of the bundle are joined at their ends by manifold boxes 36, 38 (likewise 46, 48 for the bundle 44 of the module 40). The manifolds 36, 38 consist of an alternating stack of hollow plates allowing the circulation and distribution of the refrigerant gas, and spacer plates for defining the interval between the successive tubes of the bundle. Reference can be made to the aforementioned FR-A-2 852 383 for the detailed description of various embodiments of such a bundle of tubes provided with its end collector boxes. As can be seen in particular in FIGS. 3 and 4, the refrigerant gas introduced through the inlet 26 is distributed by the manifold 36 so as to distribute the circulation of this gas under high pressure in the various channels of the various Beam tubes 34. At the opposite end, the manifold 38 connects the different channels of the different tubes to direct the flow of gas to the manifold 48 of the lower module 40 immediately below the manifold 38. The gas then flows through the bundle of tubes 44 of the lower module 40 in the opposite direction from the one in which it was circulating in the bundle 34 of the upper module, and this until the opposite end, to reach the header box 46. The flow gas is then directed from the manifold 46 to the manifold 36 'of the upper module of the exchanger WGC3, where it will follow a circuit comparable to that which it followed in the sample. Beur WGC2, that is to say via the manifold 36 ', the bundle of tubes of the upper module 30', the collector boxes 38 'and 48', the bundle of tubes of the lower module 40 ', then the collector box 46 'before reaching the gas outlet 28.

The circuit traversed by the coolant coolant in the exchanger WGC2 will now be described.

The liquid is admitted through the inlet pipe 42 located at one end of the lower module 40 of the exchanger WGC2. The liquid will flow to the other end of the same module, countercurrent to the direction of flow of the gas (see in particular Figure 3), passing between the tubes of the beam. Disruptive elements of the exchanger may be provided, in a manner known per se, to increase the turbulence of the liquid flow and thus promote heat exchange with the tubes of the beam with which this fluid is in contact. contact. Once arrived at the opposite end of that where the intake manifold 42 is located, the heat-transfer liquid is placed in communication (by means that will be explained below) with the upper module 30, where it will be able to circulate to the opposite extremity: Lte, always against the current with the gas flowing in this module 30, until reaching the outlet pipe 32. The circulation of the coolant liquid is similar in the modules 30 'and 40' of the very low temperature exchanger WGC3. Thus, the gas circulating in the successive tube bundles of the exchangers WGC2 and WGC3 will be able to be cooled, from one module to another, by the circulation of the coolant, always against the current with the gas. We will now describe the manner in which the casings enclosing the bundles of tubes of the different modules are made. The structure of the housing of the module 30 will be described more precisely, that of the modules 40, 30 'and 40' being comparable, with the differences that will be indicated.

The housing of the module 30 consists of a U-shaped element 50 comprising a bottom wall 52 extending parallel to the bundle of tubes 34, below and at a distance from it, with two side walls 54, 56 The assembly is formed by a flat top member 58 forming a cover. The bottom wall 52 also constitutes the upper wall of the casing of the lower module 40, acting as a cover for the latter.

The manifolds 36 and 38 are brazed to the walls 52, 54, 56 and 58 so as to seal the housing there. The tubes of the bundle 34 are, moreover, brazed to the lateral walls 54, 56, at least on the central part of these walls, so as to mechanically stiffen the bundle of tubes and enable it to withstand the very high pressures of the refrigerant gas. .

At the opposite end of the tubing 32, the bottom wall 52 of the casing 50 is provided with orifices 60 allowing the heat transfer fluid to pass through this wall in order to put in communication the internal volume of this upper module. 30 with the interior volume of the lower module 40.

Furthermore, in line with these orifices 60, the lateral walls 54, 56 have enlarged regions 62 making it possible, as can be seen in the section of FIG. 5, to ensure the circulation of the coolant liquid over any the height of the bundle of tubes 34, so as to supply 30 by the coolant flow all the intervals between the different tubes of the bundle. It will be noted that the tubes of the bundle are situated at a distance from the side wall 54, 56 in this enlarged region 62, and are not in contact with this wall, while they are in contact and brazed with the wall in the crankcase area beyond enlarged regions 62.

In a comparable manner, at the opposite end are provided enlarged regions 64 in the vicinity of the outlet pipe 32, so as to allow the communication of all the intervals between the different tubes of the bundle 34 with this outlet pipe. 32. Here again, the tube bundle is located away from the side wall 54, 56 in the enlarged regions 64, the solder connection between the tubes and the wall being established only beyond this enlarged region. 64 (therefore in the part of the walls 54, 56 located between the enlarged regions 62, 64, except 15 of these regions). On the side in the vicinity of the tubing 32, the bottom wall 52 is devoid of a communication port such as 60, so as to prevent any communication at this point between the upper module 30 and the lower module 40, and thus force the liquid admitted by the inlet pipe 42 to traverse the module 40 over its entire length, then via the orifices 60, the module 30 over its entire length to the outlet pipe 32.

With regard to the circulation of the gas, the bottom wall 52 is provided, on the side of the manifolds 36 and 46, with an extension 66 coming to interpose between these two manifolds and prohibiting the communication between them. respective conduits 60, 70 of gas circulation. At the opposite end, the bottom wall is provided with a similar extension 72 which is interposed between the manifolds 38 and 48. This extension 72 is recessed with an orifice 74 for communication of the respective conduits 76, 78 of these two manifolds 38 and 48. the conformation of these elements makes it possible to force the flow of the gas arriving through the inlet 26 into the collector box 36, so that it traverses the beam of the tubes 34, then the manifolds 38 and 48 through the orifice 74, then the bundle of tubes 44 of the lower module 40, to the manifold 46. In general, the configuration that described above makes it possible to ensure a countercurrent flow of water and gas flows, within each of the modules 30 and 40 and from one module to another, thanks to a simple structure of the bottom wall 52, which on one side (that of the manifolds 38 and 48) is provided with liquid passages 60 and gas 74, and on the other side (that of manifolds 36 and 46 and manifolds 32 and 42) is devoid of liquid and gas passages. Mechanically, the extensions 66, 72 constitute a single additional layer of the stack of laminations of the manifolds: 36, 46, allowing easy assembly and soldering of the various elements.

If necessary, in particular to avoid thermal shocks, a spacer may be provided between the two exchangers WGC2 and WGC3, more precisely between the lower module 40 of the exchanger WGC2 and the upper module 30 'of the sample WGC3 , so as to mechanically separate these two bodies from the gas cooler.

FIGS. 6 to 9 illustrate an alternative embodiment in which the device of the invention incorporates in a single functional unit not only the gas cooler WGC (more precisely, the liquid / gas stages WGC2 and WGC3), but also the internal gas / gas exchanger IHX (referenced 16 in FIG. 1). This IHX internal exchanger is in fact mounted in the refrigerant gas circulation loop directly out of the gas cooler 14, downstream of the stage WGC3, and crosses the gas circuit delivered at the outlet of the evaporator 20. Its function is to cool the high-pressure gas leaving the gas cooler 14 by the low-pressure gas leaving the evaporator 20.

It is therefore advantageous to group these elements so as to have a more compact device and to minimize the lengths of the connecting pipes.

FIG. 6 shows a unitary assembly comprising the two exchangers WGC2 and WGC3, each formed of two modules 30, 40 and 30 ', 40' configured as described with reference to FIGS. 2 to 5. The unitary assembly also incorporates the exchanger The IHX gas / gas internal heat exchanger, generally designated 80. This internal gas / gas exchanger IHX has substantially the same overall length and width as the WGC2 and WGC3 heat exchangers. to constitute a homogeneous block grouping in the vicinity of the compressor the maximum of elements contributing to the heat exchange and cooling of the gas.

This configuration is however not limiting. The length of the IHX internal heat exchanger is not related to that of the WGC gas cooler; the internal heat exchanger IHX may be more or less long, since the output connection 5 of the gas cooler WGC3 is common to the inlet of the internal heat exchanger IHX. Figures 7 to 9 illustrate more precisely the structure of the IHX internal heat exchanger 80. This is formed of a stack of flat elements 82, 84 mounted alternately. The flat elements 82 (shown in plan in FIG. 8) are intended to be traversed by the high-pressure hot gas delivered at the outlet of the exchanger WGC3. They each comprise a multichannel tube 86 of the same nature as the multichannel tubes described above tube bundles liquid / gas exchangers WGC2 and WGC3. The channels of each tube are communicated at their ends by a nozzle 88 or 90, respectively, forming a collector. The flat elements 84 are intended to be traversed by the cold gas at low pressure from the evaporator and returning to the compressor. The structure of these flat elements 84 (illustrated in Figure 9) and similar to that of the flat elements 82, with a multichannel tube 92 provided at each end of a nozzle 94 or 96, respectively, forming collector.

The tubes 86, 92 tubes are stacked alternately to form two sets of nested tubes, where the hot gas under high pressure and the cold gas under low pressure circulate countercurrently in successive layers of stacking. The adjacent tubes 86 and 92 of each series of tubes are in mutual contact, so as to allow heat exchange by conduction between the tubes.

The number of tubes 86, 92 whose stack comprises the IHX internal heat exchanger depends on the length and the hydraulic diameter of the low pressure circuit and the high pressure circuit, and will be adapted according to the circumstances. The end collector tips 88, 90 and 94, 96 are respectively configured to stack end collector boxes to selectively dispense the refrigerant gas for both high pressure and low pressure circuits. the various tubes of the stack. Thus, the cold gas at low pressure passes through an orifice 98 of the nozzle 88, without communication with the tube 86 which is part of the high pressure circuit, while on the opposite side, the high pressure fluid circulating in this tube 86 is collected by an enlarged opening 100 allowing communication with the rest of the high pressure circuit. In the same way, the nozzle 94 comprises an enlarged opening 102 allowing communication with the low pressure circuit, and in communication with the orifice 98. In contrast, the tip 96 comprises an isolated orifice 104 allowing the crossing high pressure hot fluid without communication with the tube 92 traversed by the low pressure fluid. At the lower end of the stack, elements 106, 108 make it possible to connect the remainder of the low pressure side refrigerant circuit 2906357 24, that is to say from the evaporator 20 to compressor 10 (Figure 1).

In the upper part of the stack, the high pressure refrigerant gas is directly admitted from the collector box 46 'of the module 40' of the exchanger WGC3 (FIG. 6), thanks to a suitable dimensioning of the end pieces forming the respective manifolds of the IHX internal heat exchanger and the WGC2 and WGC3 liquid / gas heat exchangers. In other words, the stacking of the elements that form the manifolds is sufficient to ensure the direct communication of the outlet of the exchanger WGC3 with the inlet of the exchanger IHX, in the same way as was performed the direct communication of the output of the exchanger WGC2 with the inlet of the exchanger WGC3. Heretofore, the different technologies employed for making WGC exchangers and IHX exchangers, respectively, made it difficult or impossible to integrate them into one and the same element consisting of two exchange zones. It was then necessary to provide for the assembly and connection of these elements at least four connection flanges, with their screws and seals, and a hose resistant to the very high pressure of the gas. The advantageous solution of the invention makes it possible to mechanically and functionally combine the gas cooler WGC and the internal exchanger IHX. This allows, in addition to the removal of the flanges, screws, joints and high pressure pipes (thereby reducing the risk of leakage), to minimize the length of the connections of these exchangers to the compressor. An advantage which results therefrom is the reduction of the refrigerant gas volume in the circuit, with correspondingly a reduction in the size of the gas accumulator 22 which, according to the architecture of the circuit, can furthermore contribute to a better distribution. volumes of the refrigerant gas in the loop.

Yet another advantage of integrating the IHX internal heat exchanger with the WGC2 / WGC3 gas cooler is the improvement of the overall thermal performance of the circuit under difficult operating conditions, especially at high ambient temperatures. Finally, from the technological point of view, in addition to the removal of the flanges, screws, joints and high-pressure pipes, the structure that has been described allows a common and simultaneous brazing of housings, bundles of tubes and collector boxes. three exchangers WGC2, WGC3 and IHX.

Claims (23)

claims   1. Heat exchanger (30, 40; 30 ', 40') between a first fluid and a second fluid, said heat exchanger comprising an interior space and a bundle of tubes (34, 44), provided in said interior space, wherein the first fluid circulates and is cooled by the second fluid, and wherein the second fluid is introduced into the heat exchanger through an inlet manifold and discharged through an outlet manifold and occupies said interior space of the exchanger of heat, characterized in that it defines at least two passes for the second fluid.   2. Heat exchanger according to claim 1, characterized in that it defines at least two passes for the first fluid.   3. Heat exchanger according to claim 1, characterized in that the first fluid is a gas.   4. Heat exchanger according to claim 1 or 2, characterized in that the second fluid is a liquid. 25   5. Heat exchanger according to one of claims 1 to 4, characterized in that said interior space comprises at least two casings, each of said casings enclosing a plurality of tubes (34; 44) and delimiting a pass for the first fluid. 30   6. Heat exchanger according to claim 5, characterized in that the two casings have a common wall (52) comprising at least one orifice (60) for placing in communication the interior space of said two casings.   7. Heat exchanger according to claim 6, caracté-5 5 ized in that the common wall (52) extends parallel to the bundle of tubes (34; 44).   8. Heat exchanger according to one of claims 1 to 7, characterized in that it comprises manifolds 10 (36, 38), arranged at the ends of the beam (34, 44), able to collect and put in communication the tubes of the bundle (34 and 44) at their ends, these manifold boxes (36, 38) being able to be furthermore connected to a circulation circuit of the first fluid. 15   9. Heat exchange module (WGC2; WGC3), characterized in that it comprises at least two adjacent heat exchangers according to claim 8, with a first heat exchanger (30) and a second heat exchanger. their (40), one of the heat exchangers (40) is connected to an inlet mouth (42) and the other heat exchanger (30) is connected to an outlet pipe (32), these two pipes being capable of being placed in communication with a circuit of the second fluid, and the two heat exchangers have a common wall (52) extending parallel to the tube bundle and comprising at least one orifice (60) for communicating the interior space of the first heat exchanger with the interior space of the second heat exchanger. 2906357 28   10. Heat exchange module according to claim 9, characterized in that the fluid inlet and outlet pipes (32, 42) are disposed at the same respective end of the first heat exchanger and the second heat exchanger. Wherein the heat exchange port (s) (60) are disposed in the region of the opposite end of the first heat exchanger and the second heat exchanger. 10   11. Heat exchange module according to claim 9, characterized in that each heat exchanger comprises a housing (50) with two side walls vis-à-vis (54, 56) between which extends transversely the beam of the tubes (34), and in that the transverse dimension separating these walls is substantially the same as that of the tube bundle, with the exception of enlarged lateral regions (62, 64) situated in the vicinity of the tubing ( 32) and (s) 1 '(or) orifice (s) of communication (60). 20   12. Heat exchange module according to claim 11, characterized in that the side walls (54, 56) and the bundle of tubes (34) are brazed together in the region where the transverse dimension separating these walls is substantially the same. than that of the tube bundle.   13. Heat exchange module according to claim 9, characterized in that: the manifolds (36, 38; 46, 48) are formed of a superposition of plates forming alternately fluid passage and spacer for selective distribution the first fluid in the various tubes of the bundle, and the wall (52) common to the two heat exchangers comprises in the longitudinal direction an extension (66) extending into the superposition of plates forming the manifolds, this extension forming a partition 5 for the circulation of the first fluid in the manifolds (36, 46) located on either side of this partition.   14. Heat exchange module according to claim 9, characterized in that: said at least two adjacent heat exchangers (30, 40) are two main heat exchangers forming a first heat exchanger stage (WGC2) at least two adjoining auxiliary heat exchangers (30 ', 40') forming a second exchanger stage (WGC3), separate from and connected with the first exchanger stage, and the collector boxes are provided; first and second exchanger stages are interconnected successively in series so as to allow the circulation of the first fluid successively in the first and the second exchanger stage.   15. The heat exchange module as claimed in claim 14, characterized in that it comprises a wall common to the two exchanger stages, devoid of a communication orifice of the respective interior volumes of the heat exchanger casings located on the one side. and other of this common wall. 30   16. Heat exchange module according to claim 14, characterized in that it comprises between the two heat exchangers a spacer element interposed by mat 30635 30 to define a gap between the heat exchangers vis-à-vis -vis the first stage exchanger and second stage exchanger. 5   17. Heat exchange module according to claim 14, characterized in that the outlet pipe of the first exchanger stage is connected to the inlet pipe of the second exchanger stage so as to allow the circulation of the second fluid successively in the first stage. then the second exchanger stage.   18. Heat exchange module according to claim 9, characterized in that it further comprises an internal heat exchanger stage (IHX) comprising a stack of elongated multichannel tubes (86, 92), these tubes being contiguous and alternately stacked in two sets of nested tubes, with a first series of tubes (86) connected to the outlet (s) of the heat exchanger (s) so as to be traversed by the first fluid at high pressure (HP) deli 20 vre by this (these) heat exchanger (s), and a second series of tubes (92) adapted to be connected to a low pressure branch (BP) of the circuit of the first fluid so as to be traversed by the first cold fluid circulating in this branch. 25   19. Heat exchange module according to claim 18, characterized in that the internal exchanger stage (IHX) is configured adjacent to the assembly formed by the first and second heat exchange stages (WGC2, WGC3).   20. Heat exchange module according to claim 18, characterized in that the internal exchanger stage (IHX) comprises manifolds (88, 90, 94, 96) disposed at opposite ends of the stack of tubes, capable of assembling and communicating at their ends the respective tubes (86, 92) of the two series of tubes and selectively distributing the first fluid, these collector boxes further comprising means (106, 108). connecting to the first fluid circuit.   21. Heat exchange module according to claim 20, characterized in that the manifolds (88, 90, 94, 96) of the internal exchanger stage (IHX) are arranged in the alignment of the manifolds (36). , 38, 46, 48) heat exchangers (30, 40, 30 ', 40') of the first and second heat exchanger stages (WGC2, WGC3). 15   22. Heat exchange module according to claim 21, characterized in that the manifolds (88, 90, 94, 96) of the internal exchanger stage (IHX) connected to the first series of tubes (86) are connected. in series with the manifolds (36, 38, 46, 48) of the heat exchangers (30, 40, 30 ', 40') of the first and second heat exchanger stages (WGC2, WGC3) so as to allow the supply of the internal exchanger stage by the high pressure hot fluid delivered directly by the first and second heat exchanger stages. 25   23. Air conditioning equipment for a motor vehicle, characterized in that it comprises a heat exchanger according to one of claims 1 to 8, or a heat exchange module according to one of claims 9 to 22.