WO2008061918A1

WO2008061918A1 - Internal heat exchanger for cooling fluid circuit

Info

Publication number: WO2008061918A1
Application number: PCT/EP2007/062287
Authority: WO
Inventors: Carlos Martins; Anne-Sylvie Magnier-Cathenod
Original assignee: Valeo Systemes Thermiques
Priority date: 2006-11-21
Filing date: 2007-11-13
Publication date: 2008-05-29
Also published as: FR2908871B1; EP2097704A1; FR2908871A1

Abstract

The invention relates to an internal heat exchanger (3) for a cooling fluid circuit, including at least first tubes (4) for circulating the high-pressure cooling fluid and means alternating with the first tubes (4) for circulating the low-pressure cooling fluid, characterised in that said means include at least one disturber (5).

Description

Internal heat exchanger for refrigerant circuit

The invention relates to the field of heat exchangers, particularly for motor vehicles.

An internal heat exchanger is generally used for the gaseous refrigerant circuits, in particular of the CO ₂ type

In a circuit of this type, the coolant 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, an expander, an evaporator and an accumulator, as well as connecting ducts. The high pressure refrigerant fluid from the compressor is cooled in the gas cooler, then passes into a first portion of the internal heat exchanger, the portion comprising the high pressure conduits / passes and is then 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 heat exchanger, the portion comprising the low pressure conduits / passes, 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 refrigerant coming out of the gas cooler by the low pressure refrigerant exiting the evaporator. Such an internal exchanger makes it possible to improve the performance under difficult operating conditions, in particular for high ambient temperatures.

Conventionally, an internal heat exchanger for a refrigerant circuit comprises a first header and a second header, first tubes for the circulation of the high-pressure refrigerant and second tubes alternating with the first tubes for circulation against -current refrigerant fluid at low pressure.

Examples of prior art internal exchangers are disclosed in JP 2003 279276, US 6,434,972, JP 2003 121086, JP 2001 153571, JP 2004 347258 and JP 2003 202197.

In known internal heat exchangers, the use of tubes for low pressure circulation is not optimal for several reasons.

First, the micro-channel tubes generate a lot of pressure losses, which has a direct and harmful influence on the heat exchange between the fluid at two different pressures / temperatures.

Furthermore, the brazing between the channels, high pressure and low pressure, is particularly difficult and never completely satisfactory in the long term (porosity between the high and low pressure tubes) Finally, for reasons of industrialization of the current internal exchangers, the high and low pressure tubes, obtained by extrusion, are identical so that the thickness of the low pressure tubes is oversized with respect to its necessary pressure resistance.

The object of the invention is in particular to overcome the disadvantages of the prior art mentioned above,

It aims essentially to provide an internal heat exchanger that mainly, but not exclusively, to reduce the pressure drop through the increase of the passage section.

The invention proposes for this purpose an internal heat exchanger for a refrigerant circuit, comprising at least first tubes for the circulation of the high-pressure refrigerant and means alternating with the first tubes for the circulation of the coolant at low temperatures. pressure, characterized in that said means comprise at least one disrupter.

More specifically, it will be possible to define the internal heat exchanger according to the invention in that the said means consist of a plurality of disrupters.

Of course, the distinction between high and low pressure ducts / passes is totally related to the nature and the state of the fluid considered, generally here a supercritical fluid, but the high pressure, or the conduits / passes conveying it, is always present. a pressure higher than the low pressure, or the conduits / passes conveying it.

The term "disrupter" is understood to mean in particular the representations illustrated in FIGS. 5a, 5b and 5c. Thus, the disrupters of the invention may consist of a folded sheet which optionally ensures the sealing of the low pressure pass and being in contact with the adjacent high pressure tubes. The disturbers may consist of a corrugated sheet in its length and their profiles may have interruptions in its undulations except the side walls or have embossed or cut. The disrupters may consist of a grid, that is to say, corrugations or crenellations having different ranks offset relative to each other, this realization being well known to those skilled in the art.

The disrupters are distinguished from the tubes essentially in that they consist of a sheet or the like folded (s) open at least partially, that is to say that this sheet does not close on itself to form intrinsically one or conduit (s) or channel (ux).

The disrupter of the internal exchanger according to the invention makes it possible to bring the plating to facilitate brazing with the extruded tubes and the blade heads. This is a very important advantage over the stack of extruded tubes of internal exchangers of the prior art, on which it is necessary to report active flux. The porosity problem is due to an excessive tube / tube contact surface which degrades the thermal conduction. Furthermore, the internal heat exchanger according to the invention, by the use of disrupters to replace the tubes, allows significant weight savings and cost reductions.

Finally, the disturbers offer a great flexibility from a geometrical point of view, and thus a setting up and an easy assembly.

Other features of the internal heat exchanger are shown below.

According to a possibility offered by the invention, the disturbers will present lateral closure means. In this way, the disrupters of the invention form the housing or the closure envelope between the high pressure tubes.

Advantageously, these closing means will consist of raised side portions extending said disturbers. These raised lateral parts ideally have a C-profile.

Alternatively or in addition to the aforesaid means for closing disrupters, it may be provided an insert housing, intended in particular to (in) sideways close the ducts / low pressure passes.

Advantageously, the upper and lower walls of a passage through which the low-pressure refrigerant circulates are formed by an outer wall of two contiguous tubes. The present invention relates to an integrated assembly of heat exchangers comprising at least one heat exchanger for cooling a refrigerant, characterized in that it comprises an internal exchanger as described above also for cooling said refrigerant.

In the description which follows, made only by way of example, reference is made to the appended drawings, in which:

- Figure 1 is a front view of an integrated assembly according to the invention, comprising a gas cooler and the internal heat exchanger of the invention;

- Figure 2 is an exploded view of the internal heat exchanger according to the invention without housing;

Figure 3 is a schematic side view of an internal heat exchanger according to the invention with housing;

Figure 4 is a side view of the longitudinal section, cut purely to illustrate the ends, of the internal heat exchanger according to the invention;

- Figures 5a, 5b and 5c each show an example of a disrupter inserted in the internal heat exchanger according to the invention.

The invention finds particular application to air conditioning systems for motor vehicles. FIG. 1 shows an integrated assembly 1 comprising a gas cooler 2 and an internal exchanger 3 having a first portion or high pressure path and a second portion or low pressure path. A complete air conditioning circuit, in which is included the internal heat exchanger 3 and / or the integrated assembly 1 according to the invention, further comprises in particular a compressor, an expander, an evaporator and a coolant accumulator not shown in the accompanying figures.

The interactions and exchanges of refrigerant, both at low pressure and at high pressure, are carried out in accordance with the known devices and are not modified in the present invention which can be adapted in particular to all types of air conditioning circuit.

Thus, the hot refrigerant fluid and high pressure from the compressor is cooled in the gas cooler 2 by heat exchange with a flow of air. At its outlet from the gas cooler 2, the hot and high-pressure refrigerant circulates in the first part of the internal exchanger, that is to say the part constituted by conventional tubes 4, where it exchanges heat. with the same refrigerant fluid and low pressure flowing in the second part, the subject of the invention and consisting of disruptors 5. The fluid is then expanded in the expander and brought to low pressure, it then passes through the evaporator then the accumulator and finally the second part of the internal heat exchanger 3, as already indicated, before returning to the compressor. FIG. 2 illustrates the various elements constituting the internal heat exchanger 3 according to the invention and, at the bottom of the figure, these elements assembled together to form the internal heat exchanger 3.

Thus, the internal heat exchanger 3 comprises a cheek 6 forming an end cap and disposed in the upper stage of the stack of tubes 4 and disrupters 5. The tubes 4 and the disrupters 5 are then positioned in position. below the others successively so that once made the fixing, conventionally by brazing, between a disrupter and the two contiguous tubes, namely the fixing to the lower tube and the upper tube, each conduit or low pressure pass is formed by a disrupter 5 and the walls or outer walls of the two adjacent tubes constituting the upper and lower walls of the duct / low-pressure pass.

End elements 7, not specific to the object of the present invention, are arranged and fixed to the longitudinal ends of each tube 4 and disrupter 5 to conventionally allow the passage of both types of fluid, low pressure and high pressure, respectively in the disturbers 5 and in the tubes 4.

The internal heat exchanger 3 shown in Figure 2 comprises two fastening flanges 8 forming inlet and / or outlet pipe for the fluid or both (s). Note that the present invention applies that the internal heat exchanger 3 has a diffusion of the two fluids in the opposite direction or in the same direction. FIG. 3 illustrates an internal heat exchanger 3 comprising a complementary casing 9 intended primarily to close the sides of the low pressure passes and to reinforce the mechanical cohesion, if any, of the assembly formed of the tubes 4 and the disrupters 5. As can be seen as can be seen in the figure, the plate forming the casing 9 is folded to penetrate inside each low-pressure pass 10 and then soldered to the ends of the tubes 4 so that the assembly comprising the tubes 4, the disrupters 5 and the casing 9 forms a unitary and compact whole.

FIG. 4 schematically illustrates an internal exchanger 3 according to the invention where the superposition or stacking of the tubes 4 and the disturbers 5 is visualized.

The internal heat exchanger 3 has a high pressure inlet and a high pressure outlet, as well as a low pressure inlet and a low pressure outlet. Since the refrigerant flows countercurrently in both parts and the internal heat exchanger 3, the high pressure inlet and the low pressure outlet are at a first end of the exchanger, while the low inlet pressure and the high-pressure outlet are at another end of the heat exchanger 3. An internal exchanger 3 may also be provided in which the

The low pressure outlet and the high pressure outlet are located at the same end of the internal heat exchanger.

The connectors used to report the flanges 8 can be soldered directly to the low pressure inlet, ie the inlet for the low-level coolant. pressure, and the low and high pressure exits of the internal heat exchanger 3. The connectors slip into a groove made in the blade heads 7, on the height corresponding to the connection, thus ensuring the maintenance in vertical and horizontal position.

The disruptors 5, 5 ', 5 "are brazed to the lower and upper tubes so that the low pressure passes are formed in part by the contiguous upper and lower walls, thus avoiding two thicknesses of tube, or more exactly two thicknesses corresponding to the distance between the ducts of a tube and the outer surface of this tube, because, thanks to the invention, possibly only a sheet thickness is added to the thickness or the said distance this makes it possible to significantly improve the heat exchange between the fluids at two different pressures.

FIGS. 5a, 5b and 5c show three examples of disruptors 5, 5 'and 5 "having, at their two lateral ends, a C-shaped return 11 so as to have a flat portion 12 extending parallel to the surface of the tubes in order to to be brazed with the latter, when the disturbers 5, 5 'and 5 "are contiguous with the tubes 4.

In FIG. 5a, the disrupter 5 'consists of a flat sheet whose two flanges 11 are curved in return, these two flanges 11 extending in the direction of one another and comprising a flat part 13' extending parallel to the central flat or lower portion 12. In FIG. 5b, the disrupter 5 "is identical to the disrupter 5 'of FIG. 5a and has a plurality of localized protuberances 14 extending from its flat internal face 12, constituting as many irregularities favoring the heat exchange between fluids at different pressures.

In FIG. 5c, the disrupter 5 "is identical to the disrupter 5 'of FIG. 5a and comprises corrugations 15 stretching over the entire length of the disrupter 5" so that the section of this disrupter has a a plurality of sinuosities or meanders terminated at both ends by the return to C 11.

It will of course be possible to envisage, in particular, a disrupter combining the shapes and characteristics of the disrupters 5, 5 'and 5 "shown in FIGS. 5a, 5b and 5c.

The disruptors 5, 5 'and 5 "are shorter than the tubes 4 for the circulation of the high-pressure refrigerant These disrupters 5, 5' and 5" are centered with respect to the tubes 4 at high pressure, the sealing at Box level is ensured by the low pressure blade head and the high pressure tube. The use of these disturbers avoids the problem of porosity between the high and low pressure tubes.

Claims

claims

1. Internal heat exchanger (3) for a refrigerant circuit, comprising at least first tubes (4) for the circulation of the high-pressure refrigerant and means alternating with the first tubes (4) for the circulation of the fluid refrigerant at low pressure, characterized in that said means comprise at least one disruptor (5, 5 'or 5 ").

2. Internal heat exchanger (3) according to claim 1, characterized in that the disruptor (5, 5 'or 5 ") has lateral closing means (11).

3. Internal heat exchanger (3) according to claim 2, characterized in that these closing means (11) consist of raised side portions extending said disruptors (5, 5 'or 5 ").

4. Internal heat exchanger (3) according to claim 3, characterized in that these side portions (11) raised ideally have a profile C.

5. internal heat exchanger (3) according to any one of the preceding claims, characterized in that it comprises a housing (9) reported, for (in) laterally close the ducts / low pressure passes.

6. Internal heat exchanger according to any one of the preceding claims, characterized in that the disruptor (5, 5 'or 5 ") comprises a plurality localized protuberances (14) extending from its planar inner face (12).

7. internal heat exchanger (3) according to any one of the preceding claims, characterized in that the disruptor (5) comprises undulations stretching over the entire length of the disrupter (5, 5 'or 5 ").

8. internal heat exchanger (3) according to any one of the preceding claims, characterized in that said means consist of a plurality of disruptors (5, 5 'or 5 ").

9. internal heat exchanger (3) according to any one of the preceding claims, characterized in that the walls, upper and lower, a pass in which circulates the low-pressure refrigerant are formed by an outer wall of two tubes (4) contiguous.

10. Integrated heat exchanger assembly comprising at least one heat exchanger (2) for cooling a refrigerant, characterized in that it comprises an internal heat exchanger (3) as claimed in one of the preceding claims for cooling said coolant.