FR2906353A1 - Internal heat exchanger for motor vehicle, has flat tubes supplying low pressure outlet so as to form high pressure and low pressure outlets at same end of exchanger, where tubes provide reverse circulation of low pressure refrigerant - Google Patents

Abstract

The exchanger (16) has flat tubes (56) for circulating high pressure refrigerant e.g. carbon dioxide, and flat tubes (58), which alternates with the tubes (56), for reverse circulation of low pressure refrigerant. The tubes (56) supply a return tube (56R) to parallely circulate the high pressure refrigerant with low pressure refrigerant, and a high pressure outlet (26). The tubes (58) supply a low pressure outlet (30) so as to form the high pressure and low pressure outlets at a same end of the exchanger. An independent claim is also included for an integrated assembly for gaseous coolant circuit, comprising a gas cooler.

Description

1 Internal heat exchanger for refrigerant circuit

  The invention relates to the field of heat exchangers, particularly for motor vehicles. It relates more particularly to an internal heat exchanger for a refrigerant circuit, comprising a first collector and a second collector, first tubes for the circulation of the high-pressure refrigerant and second tubes alternating with the first tubes for circulation at countercurrent of the refrigerant fluid at low pressure.

  It applies in particular to gaseous refrigerant circuits, in particular of the CO2 type. In a circuit of this type, the cooling fluid remains essentially in the gaseous state and under a very high pressure which is usually between 100 and 150 bar. Such a circuit is advantageously made in the form of a motor vehicle air conditioning circuit.

  A circuit of this type essentially comprises a compressor, a gas cooler, an internal heat exchanger of the aforementioned type, an expander and an accumulator, as well as connecting ducts. The high pressure coolant from the compressor is cooled in the gas cooler, then passes into a first portion of the internal heat exchanger, and is expanded by the expander. The low pressure fluid leaving the expander then passes through the evaporator, the accumulator and into a second portion of the internal exchanger before returning to the compressor. The internal heat exchanger is mounted at the outlet of the gas cooler and the evaporator, its function being to sub-cool the high-pressure coolant exiting the gas cooler by the low-pressure coolant exiting the evaporator. Such an internal exchanger makes it possible to improve performance under difficult operating conditions, especially at high ambient temperatures. Examples of internal exchangers of the prior art are described in JP Patent Publications 2003 2003 279276, US 6 434 972, JP 2003 121086, JP 2001 153571, JP 2004 347258 and JP 2003 202197. In known internal exchangers, the Flow of the fluid in the two parts of the exchanger is carried out in countercurrent resulting that the inputs and outputs are located at both ends of the exchanger, which does not facilitate their connection to a chiller. gas. In particular, this connection requires additional tubing of the gas cooler outlet at the inlet of the internal heat exchanger to provide countercurrent flow for the fluids. In addition, it is most often desired to provide an integrated assembly comprising the gas cooler, the internal heat exchanger and the refrigerant accumulator, also called a bottle. An additional difficulty lies in the fact that the accumulator must be equipped with a support, or an additional tubing, for its connection to the internal heat exchanger. The object of the invention is in particular to overcome the disadvantages of the prior art. It aims essentially to provide an internal heat exchanger of the type mentioned in the introduction which facilitates the connection and reduce the number of connections 10 of the air conditioning circuit in which it is provided. The invention proposes for this purpose an internal heat exchanger, of the type mentioned above, wherein the first 15 tubes feed a return tube adapted to circulate the high-pressure refrigerant cocurrent with the refrigerant fluid at low pressure and feeding a high pressure outlet, while the second tubes supply a low pressure outlet.

Due to the presence of this return tube, the high pressure outlet and the low pressure outlet may be located at the same end of the heat exchanger to facilitate connections, in particular with the gas cooler. Thus, the return of the refrigerant fluid at high pressure is integrated in the internal heat exchanger and this return tube is advantageously used as a heat exchange surface, thus contributing to improving the thermal performance of the internal heat exchanger .

Further characteristics of the internal heat exchanger are indicated below: a first manifold defines an inlet chamber for the high pressure refrigerant which supplies the first tubes and an outlet chamber for the fluid low pressure refrigerant which is fed by the second tubes and feeds the low pressure outlet, while a second manifold defines an inlet chamber for the low pressure refrigerant which feeds the second tubes and an outlet chamber for the high pressure refrigerant which is fed by the first tubes and feeds the return tube, said return tube supplying the high pressure outlet formed in the first manifold. The first tubes and the second tubes are flat tubes stacked so as to form a bundle opening into the first collector on a first face of the bundle and opening into the second collector on a second face of the bundle. The ends of the first tubes and the ends of the second tubes are offset in the longitudinal direction of the tubes. The inlet chamber of the first manifold associated with the first tubes is limited in the stacking direction by faces of the first manifold and the outlet chamber of the first manifold associated with the second tubes is limited in the stacking direction by faces of first adjacent tubes. The inlet chamber of the second manifold associated with the second tubes is limited in the stacking direction by faces of the second manifold and the outlet chamber of the second manifold associated with the first tubes is limited in the stacking direction. by faces of second adjacent tubes. The first collector consists of mutually stacked plates, the faces of each plate of the collector being located substantially in the same plane as the faces of the associated tube. The second collector consists of mutually stacked plates, the faces of each plate of the collector being located substantially in the same plane as the faces of the associated tube. The first manifold has an inlet for the high pressure refrigerant fluid which extends in the stacking direction and the second manifold has an inlet for the low pressure refrigerant fluid which extends in the stacking direction. Said first manifold inlet is formed in a first end flange arranged to be connected to a gas cooler, and said second manifold inlet is formed in a second end flange forming a support flange for a fluid accumulator. . The first manifold further comprises, opposite the first end flange, an outlet flange having two pipes respectively corresponding to the high pressure outlet and the low pressure outlet. 2906353 6 - The return tube is one of the first tubes. In another aspect, the invention relates to an integrated assembly for a gaseous refrigerant circuit, in particular of the CO 2 type, which comprises a gas cooler, a fluid accumulator and an internal heat exchanger as defined above. Other features of this integrated assembly are indicated below: The gas cooler comprises at least two tubular manifolds respectively surmounting the first manifold and the second manifold of the internal heat exchanger, and between which is mounted a heat exchange beam. A first tubular manifold box surmounting the first manifold has an inlet for the high pressure refrigerant fluid. The heat exchange bundle of the gas cooler comprises two plies, one of which is mounted between said first tubular collecting box and at least one intermediate collecting box surmounting the second collector and the other of which is mounted between the collecting box; intermediate and a second header which is adjacent to the first manifold and whose lower end feeds the first manifold high pressure refrigerant. - The fluid accumulator is fixed on a support flange from the second collector of the internal heat exchanger.

In the description which follows, given by way of example only, reference is made to the accompanying drawings, in which: FIG. 1 represents a diagram of an air-conditioning circuit operating with a gaseous refrigerant fluid of the CO2 type and comprising an internal heat exchanger; FIG. 2 is a front view of an integrated assembly according to the invention, comprising a gas cooler, an internal heat exchanger and an accumulator; FIG. 3 is a side view of the integrated assembly of FIG. 2; Figure 4 is a top view of the integrated assembly of Figure 2; FIG. 5 is a perspective view of the integrated assembly of FIGS. 2 to 4, the connections of which have been shown with the other components of the circuit; FIG. 6 is an exploded perspective view of the internal heat exchanger and the accumulator; Figure 7 is a cut-away perspective view of the internal heat exchanger and the accumulator in the assembled state; Figure 8 is an enlarged detail of Figure 7; and FIG. 9 is another enlarged detail of FIG. 7. Referring to FIG. 1, there is shown an air conditioning circuit 10 operating with a supercritical refrigerant, for example carbon dioxide (CO2), remaining essentially in the gaseous state. The circuit 10 comprises a compressor 12, a gas cooler 14, an internal heat exchanger 16 having a first portion or channel 161 (high pressure path) and a second portion or path 162 (low pressure path), a pressure reducer 18, a Evaporator 20 and a refrigerant accumulator 22. The circulation of the high-pressure refrigerant is represented by triangular arrows and that of the low-pressure refrigerant by V-shaped arrows.

The hot and high pressure coolant from the compressor 12 is cooled in the gas cooler 14 by heat exchange with a flow of air. At its outlet from the gas cooler, the hot and high-pressure refrigerant circulates in the first part 161 of the internal heat exchanger where it exchanges heat with the same cold and low-pressure refrigerant circulating in the second heat exchanger. Part 162. The fluid is then expanded in the expander 22 and brought to low pressure, it then passes through the evaporator 20 and the accumulator 22 and finally the second portion 162 of the internal heat exchanger 16, as already indicated, before returning to the compressor 12.

The internal heat exchanger 16 has a high pressure inlet 24 and a high pressure outlet 26, as well as a low pressure inlet 28 and a low pressure outlet 30.

Since the coolant circulates countercurrently in the portions 161 and 162 of the internal heat exchanger 16, the high pressure inlet 26 and the low pressure outlet 30 are at a first end of the heat exchanger, while the low pressure inlet 28 and the high pressure outlet 26 are at another end of the heat exchanger. In particular, it can be seen that the high pressure outlet 26 and the low pressure outlet 30 of the internal exchanger 16 are located at opposite ends thereof, which does not allow easy connection with the other components of the circuit, such as already indicated. The invention overcomes this disadvantage by designing an internal heat exchanger in which the low pressure outlet and the high pressure outlet are located at the same end of the internal heat exchanger. 2 to 5 which show different views of an integrated assembly comprising a gas cooler 14, an internal heat exchanger 16 according to the invention and an accumulator 22. FIG. 5 to which reference will be made mainly shows the same integrated assembly seen in perspective with its connections to the other 30 components of the circuit. In the exemplary embodiment, the gas cooler comprises two plies 32 and 34 respectively forming two 2906353 10 circulation passes. The first ply 32 is mounted between a first tubular collecting box 36 having a high pressure inlet 38 for the gaseous refrigerant fluid and at high pressure from the compressor 12. The ply 32 opens at its other end into an intermediate tubular collecting box 40 which feeds another intermediate header 42 located adjacent. The latter feeds the sheet 34 which in turn feeds a second tubular box 44 located adjacent to the tubular box 36. In the example shown, the internal heat exchanger 14 is arranged in a generally vertical manner, the manifolds 36, 40, 42 and 44 being vertical and in generally parallel directions. The two layers 32 and 34 which constitute the heat exchange bundle of the gas cooler 14 are located in planes parallel to each other and generally vertical.

The gas cooler 14 is located above the internal heat exchanger 16, the latter including a first manifold 46, a second manifold 48 and a bundle of tubes 50 extending between the manifolds 46 and 48. The manifolds 36 and 44 surmount the first manifold 46, while the manifolds 40 and 42 surmount the second manifold 48. The manifold 44 has a high pressure outlet 51, located in the lower part and directly supplying the internal exchanger 30 16. The first manifold 46 comprises a high pressure outlet 26 and a low pressure outlet 30 which are thus grouped 2906353 11 at the same end of the internal heat exchanger 16, unlike the configuration shown in FIG. 48 is provided with a support flange 52, or base, on which is mounted the accumulator 22, which is in the form of a bottle disposed generally verteme nt. This accumulator comprises a low-pressure inlet 54. The support flange 52 defines fixing means for the accumulator 22 as well as circulation means for the low-pressure refrigerant, as will be explained later. Also shown in FIG. 5 is the compressor 12 which is mounted between the low pressure outlet 30 of the internal heat exchanger and the high pressure inlet 38 of the gas cooler. Furthermore, the high pressure outlet 26 of the internal exchanger is connected to the expander 18, which is then connected to the evaporator 20 which, at the output, is connected to the low pressure inlet 54 of the accumulator 22. see from the arrows that the high pressure fluid entering through the inlet 38 of the gas cooler 14 flows successively in the plies 32 and 34 before leaving the gas cooler 14 through the outlet 51 to open into the first manifold 25 46 of the internal heat exchanger 16. In the exchanger 16, the high-pressure refrigerant circulates in a first part of the bundle (arrow F1) where it exchanges heat with the low-pressure coolant (arrow F3) which comes from the accumulator 22 to gain the low pressure output 30. However, the high pressure gaseous coolant leaves the manifold 48 to form a return (arrow F2) 2906353 12 circulating in co-current with the fluid e at low pressure (arrow F3) and gain the low pressure outlet 30 of the collector 46. This return of the high pressure refrigerant (arrow F3) is achieved by a particular arrangement 5 of the internal heat exchanger, as we will see now in FIG. 6. The internal heat exchanger 16 comprises a bundle of tubes formed by an alternating stack of first tubes 56 (in the example four in number) and second tubes 58 (in the example to the number of five). In the first three tubes 56, the circulation of the high-pressure fluid from the gas cooler 14 is from left to right in the drawing, as shown by the three arrows F1. On the other hand, the circulation of the fluid in the first tube located at the bottom (referred to as the return tube 56R) is effected in the opposite direction as shown by the arrow F3 for supplying the high-pressure outlet 26. On the other hand, the circulation of the Low pressure fluid from the accumulator 28 is made in the five tubes 58 in the direction of the five arrows F2, that is from right to left in the drawing. In other words, this circulation is carried out against the current with respect to the circulation in the first three tubes 56.

The circulation of the high pressure fluid in the return tube 56R is co-current with the circulation of the low pressure fluid in the tubes 58, while nevertheless providing a heat exchange. The first tubes 56 and the second tubes 58 are flat tubes stacked so as to form a beam opening into the first collector 46 on a first face of the bundle and opening into the second collector 48 on a second face of the bundle. The first tubes 56 and the second tubes 58 are of the same length, the ends of the first tubes and the ends of the second tubes being offset in the longitudinal directions of the tubes, as can be seen in particular in FIG. 6. Each tube 56 or 58 has a multiplicity of parallel channels 60 (Figure 9) for the flow of fluid which extend parallel to the longitudinal direction, here horizontal, the tube and opening at both ends thereof. At the respective ends of each first tube 56 are associated a plate 62 and a plate 64 and at the respective ends of each second tube 58 are associated a plate 66 and a plate 68. The plates 62 and 64 associated with a first tube 56 have main faces located in the same planes as the two main faces 20 of this tube, and therefore have the same thickness as this one. Likewise, the plates 64 and 68 associated with a second tube 58 have principal faces located in the same planes as the two main faces of this tube, and therefore have the same thickness as this one. In the illustrated example, this thickness is the same for the tubes 56 and for the tubes 58. Each of the plates 62, 64, 66 and 68 comprises a main part 70 extending opposite the end of the tube 30 over any the width thereof, and two lateral flanges 72 and 74 coming into sealing contact, after soldering, respectively with two opposite longitudinal edges of the tube, in the vicinity of its end. Between the main portion 70 of each plate and the corresponding tube end is a fluid collection space 76 into which all channels of the tube open.

As can be seen more particularly in FIGS. 6 and 7, the assembly formed by a first tube 56 and its associated plates 62 and 64, as well as the assembly formed by a second tube 58 and its associated plates 66 and 68 have the same outline, and these sets are mutually stacked to form a cylindrical block which constitutes either the first manifold 46 or the second manifold 48. On the other hand, although the tubes 56 and 58 are the same length, their ends are not located in the same plans. The collection spaces 76, adjacent to the ends of the tubes, also have a mutual vertical offset, this offset being such that: the recess of a plate 62 associated with a first tube 56 is delimited in the stacking direction by the two adjacent plates 66 associated with respective second tubes 58, the recess of a plate 64 associated with a first tube 56 is delimited in the stacking direction by the plane faces of the two adjacent second tubes 58, the recess of a plate 66 associated with a second tube 58 is delimited in the stacking direction by the plane faces of the two first tubes 56 adjacent, - the recess of a plate 68 associated with a second tube 58 is delimited in the stacking direction by the two neighboring plates associated with respective first tubes 56. The recesses associated with the end tubes, that is to say the second tube 58 located in the upper part and the second tube 58 located in the lower part, are formed by particular outer plates which have the same outer contour as the plates 62. to 68 previously described.

Thus, the first collector 46 is closed in the upper part by a solid plate 78 (FIGS. 6, 7 and 9) provided with a collar 80 defining an opening for introduction of the high-pressure refrigerant 15 coming from the gas cooler. 14. This first plate 78 constitutes an end flange arranged to be connected to the gas cooler. The high pressure inlet delimited by the collar 80 is aligned with circular holes 82 (FIG. 6) formed in the plates 66 associated with the second tubes 58, these holes also opening into collection spaces associated with the first three tubes 58. Thus, the high-pressure fluid can feed the first three tubes 58. It should be noted that the penultimate plate 66, from the top, is devoid of orifice 82.

On the other hand, the one immediately below is again provided with such an orifice (FIG. 6). The end plates 64 associated with the first tubes 58 are also each provided with a similar hole 84.

The uppermost plate 68 has an extension and is called 68P (FIGS. 6, 7 and 8). It is surmounted by two other plates 86 and 88, these three plates jointly forming the support flange 25 supporting the accumulator 22. It will be noted that the intermediate plate 86 has a cutout 90 communicating with a hole 92 of the plate 88 and further communicating directly with the collection space that the plate 68P houses. Hole 92 forms an entrance in the stacking direction. The cutout 90 and the hole 92 form the fluid flow means at low pressure defined by the support flange 52, as mentioned above.

Thus, the low pressure fluid from the accumulator 22 can feed the second tubes 58. The plates 68P, 86 and 88 are provided with aligned holes 94 and 96 for fixing the accumulator 28 by means of screws 98 (FIG. 6) which engage in a bottom wall of the accumulator. In the lower part, the first collector 46 is closed by a flange 100 comprising two pipes respectively defining the high pressure outlet 26 and the low pressure outlet 30 (FIGS. 6, 7 and 9). For its part, the second collector 48 is closed by an end plate 102 which is solid (FIGS. 6, 7 and 8). With this arrangement, the high-pressure fluid 25 returns to the outlet pipe 26 through the return pipe 56R, circulating in co-current with the low pressure tube which passes through the second tubes 58. The flange 100 has two orifices, a port 104 for supplying the tubing of the high pressure outlet 26 and an orifice 106 for supplying the tubing of the low pressure outlet 30 (FIGS. 6 and 9).

It is thus possible to provide an integrated assembly comprising the gas cooler, the internal heat exchanger and the fluid accumulator by reducing the number of connections and thus simplifying the production. The invention finds particular application to air conditioning systems for motor vehicles.

Claims (17)

claims   1. Internal heat exchanger for a refrigerant circuit, comprising at least first tubes (56) for the circulation of the high pressure refrigerant and second tubes (58) alternating with the first tubes for the countercurrent circulation refrigerant fluid at low pressure, characterized in that the first tubes (56) feed a return tube (56R) adapted to circulate the high pressure refrigerant fluid co-current with the refrigerant fluid at low pressure and supplying an outlet high pressure (26), while the second tubes (58) feed a low pressure outlet (30), thereby forming the high pressure outlet (26) and the low pressure outlet (30) at the same end of the internal heat exchanger (16).   2. Internal heat exchanger according to claim 1, characterized in that a first manifold (46) defines an inlet chamber for the high pressure refrigerant which feeds the first tubes (56) and an outlet chamber for the low pressure refrigerant which is fed by the second tubes (58) and feeds the low pressure outlet (30), while a second manifold (48) defines an inlet chamber for the low pressure refrigerant which feeds the second tubes (58) and an outlet chamber for the high pressure refrigerant fluid which is fed by the first tubes (56) and which feeds the return tube (56F :), said return tube supplying the high pressure outlet ( 26) formed in the first manifold (46). 18 2906353 19   3. Internal heat exchanger according to one of claims 1 and 2, characterized in that the first tubes (56) and the second tubes (58) are flat tubes 5 stacked to form a beam opening into the first collector (46) on a first face of the beam and opening into the second collector (48) on a second face of the beam. 10   4. Internal heat exchanger according to one of claims 1 to 3, characterized in that the ends of the first tubes (56) and the ends of the second tubes (58) are offset in the longitudinal direction of the tubes. 15   5. Internal heat exchanger according to one of claims 2 to 4, characterized in that the inlet chamber of the first collector (46) associated with the first tubes (56) is limited in the direction of stacking by 20 faces of the first manifold and that the outlet chamber of the first manifold associated with the second tubes (58) is limited in the stacking direction by faces of adjacent first tubes. 25   6. Internal heat exchanger according to one of claims 2 to 5, characterized in that the inlet chamber of the second collector (48) associated with the second tubes (58) is limited in the stacking direction by faces of the second collector (48) and the output chamber of the second collector associated with the first tubes (56) is limited in the stacking direction by adjacent second tube faces. 2906353 20   7. Internal heat exchanger according to one of claims 3 to 6, characterized in that the first collector (46) consists of plates (62, 66) mutually stacked, the faces of each plate of the collector being located substantially in the same planes as the faces of the associated tube.   8. Internal heat exchanger according to one of claims 3 to 7, characterized in that the second collector (48) consists of mutually stacked plates (64, 68), the faces of each collector plate being located substantially in the same planes as the faces of the associated tube. 15   9. Internal heat exchanger according to one of claims 3 to 8, characterized in that the first collector (46) has an inlet (80) for the high pressure refrigerant fluid which extends in the stacking direction and that the second manifold (48) has an inlet (92) for the low pressure coolant which extends in the stacking direction.   An internal heat exchanger according to claim 9, characterized in that said inlet (80) of the first manifold (46) is formed in a first end flange (78) arranged to be connected to a gas cooler (14). ), and said inlet (92) of the second manifold (48) is formed in a second end flange (52) forming a support flange for a fluid accumulator (22).   An internal heat exchanger according to claim 10, characterized in that the first manifold (46) further comprises, opposite the first end flange (78), an outlet flange (100) having two pipes respectively corresponding to the high pressure outlet (26) and the low pressure outlet (30). 5   12. Internal heat exchanger according to one of claims 1 to 11, characterized in that the return tube (56R) is one of the first tubes.   13. Integrated assembly for a gaseous refrigerant circuit, in particular of the CO2 type, characterized in that it comprises a gas cooler (14), a fluid accumulator (22) and an internal heat exchanger (16). according to one of claims 1 to 12. 15   14. Integrated assembly according to claim 13, characterized in that the gas cooler (14) comprises at least two tubular manifolds (36, 44; 40, 42) respectively overlying the first manifold (46) and the second manifold (48). ) of the internal heat exchanger 20 (16), and between which is mounted a heat exchange beam (50).   15. Integrated assembly according to claim 14, characterized in that a first tubular manifold 25 (36) surmounting the first manifold (46) has an inlet (38) for the high pressure refrigerant.   16. Integrated assembly according to claim 15, characterized in that the heat exchange bundle (50) of the gas cooler (14) comprises two plies (32, 34) one of which (32) is mounted between said first tubular manifold (36) and at least one intermediate manifold (40, 42) surmounting the second manifold (48) and the other (34) of which is mounted between the intermediate manifold (40, 42) and a manifold second manifold (44) which is adjacent to the first manifold (36) and whose lower end feeds the first manifold (46) with high pressure refrigerant.   17. Integrated assembly according to one of claims 13 to 14, characterized in that the fluid accumulator (22) is fixed on a support flange (52) from the second collector (48) of the heat exchanger internal (16).