FR2908871A1 - INTERNAL HEAT EXCHANGER FOR REFRIGERANT FLUID CIRCUIT - Google Patents

Abstract

The invention relates to an 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 refrigerant fluid at low pressure, characterized in that said means comprise at least one disruptor (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 cool 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 part of the internal exchanger, the part comprising the ducts / low pressure 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 leaving the gas cooler with the low-pressure refrigerant coming out of the cooler. 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 manifold and a second manifold, first tubes for the circulation of the high pressure refrigerant and second tubes alternating with the first tubes for circulation. against the current of the refrigerant fluid at low pressure. Examples of prior art internal exchangers are disclosed 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 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. Moreover, 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). Lastly, for reasons of industrialization of the internal exchangers current, 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 which mainly, but not exclusively, reduces the pressure drop by increasing 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 fluid and means alternating with the first tubes for the circulation of the refrigerant fluid. low pressure, characterized in that said means comprise at least one disruptor. 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 the high and low pressure conduits / passes is totally related to the nature and state of the fluid under consideration, generally here a supercritical fluid, but the high pressure, or the conduits / passes conveying it. , always has a higher pressure than the low pressure, or ducts / passes conveying it.

The term "disturbing" is intended 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 seals the low pressure pass and is in contact with the adjacent high pressure tubes. The disrupters 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 at least partially open, that is to say that this sheet does not close on itself to form intrinsically one or more condu = it (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 stacking of the extruded tubes of the prior art internal exchangers, to which active flux must be related. The porosity problem is due to a too large 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 gain and cost reduction. Finally, the disturbers offer a great flexibility from a geometrical point of view, and therefore an easy installation and 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 closure envelope between the high pressure tubes. Advantageously, these closing means will consist of raised side portions extending said disturbers. These raised side portions preferably have a C-profile. Alternatively or in addition to the aforesaid disruptive closure means, an attached casing may be provided, in particular for (in) closing the low-pressure ducts / passages laterally. 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 5 of heat exchangers comprising at least one heat exchanger for cooling a refrigerant fluid, characterized in that it comprises an internal exchanger as described above also for cooling said cooling fluid .

In the description which follows, given by way of example only, reference is made to the accompanying drawings, in which: FIG. 1 is a front view of an integrated assembly according to the invention, comprising a gas cooler; and the internal 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 away to essentially 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 has particular application to air conditioning systems for motor vehicles. FIG. 1 shows an integrated assembly 1 comprising a gas cooler 2 and an internal heat 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 non-refrigerant accumulator. shown in the accompanying figures. The interactions and exchanges of coolant, 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. adapt particularly to all types of air conditioning circuit.

Thus, the hot and high pressure coolant 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 25 of the internal exchanger, that is to say the part constituted by conventional tubes 4, where it exchanges the heat with the same cool refrigerant fluid and low pressure flowing in the second part, the subject of the invention and consisting of disruptors 5. The fluid 30 is then expanded in the expander and brought to low pressure, it then passes through the the evaporator then the accumulator and finally the second part of the heat exchanger 2908871 8 internal heat 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 on the upper stage of the stack of tubes 4 and disrupters 5. The tubes 4 and the disrupters 4 are then positioned one below the other successively so that Once the fixing, conventionally by brazing, has been carried out between a disrupter and the two contiguous tubes, namely the fixing to the lower tube and to the upper tube, each duct or low-pressure pass is formed by a disruptor and the external partitions or walls. two contiguous tubes constituting the upper and lower walls of the conduit / 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 disruptor 5 in order to conventionally allow the passage of the two types of fluid, low pressure and high pressure. , respectively in the disrupter 5 and in the tubes 4. The internal heat exchanger 3 shown in FIG. 2 comprises two attachment flanges 8 forming: inlet and / or outlet pipe for the fluid (s) ). Note that the present invention applies that the heat exchanger 2908871 9 internal heat 3 has a diffusion of the two fluids in the opposite direction or in the same direction. FIG. 3 illustrates an internal heat exchanger 35 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 in the figure, the plate forming the housing 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 4 forms a unitary and compact whole.

FIG. 4 diagrammatically illustrates an internal exchanger 3 according to the invention, in which the superposition or the stacking of the tubes 4 and the disturbers 5 are 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 between the two 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 The low pressure inlet and the high pressure outlet are located at another end of the heat exchanger 3. An internal exchanger 3 may also be provided in which the low pressure outlet and the high pressure outlet are placed at the same end. of the internal heat exchanger.

The fittings used to report the flanges 8 can be soldered directly to the low pressure inlet, i.e., the inlet for the low pressure refrigerant, and the low and high pressure outlets of 5 lt. internal heat exchanger 3. The connectors slide into a groove 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 tube thicknesses. 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 thickness this distance significantly improves the heat exchange between the fluids at the two different pressures: FIGS. 5a, 5b and 5c show three examples of disruptors 5, 5 'and 5 "having at their two lateral ends a return 11 in shape C so as to have a flat portion 12 extending parallel to the surface of the tubes to be brazed with the latter, when the disturbers 5, 5 'and 5 "are contiguous to the x tubes 4.

In FIG. 5a, the disrupter 5 'consists of a plane sheet whose two flanges 11 are curved in return, these two flanges 11 extending towards each other 2908871 11 and having a flat part 13 extending parallel to the central, or lower, planar portion 12. In FIG. 5b, the disrupter 5 "is identical to the disrupter 5 'of FIG. 5a and having a plurality of localized protuberances 14, extending from its flat internal face 12, constituting so many irregularities promoting heat exchange between the fluids at different pressures.

In FIG. 5c, the disrupter 5 "is identical to the disrupter 5 'of FIG. 5a and comprises corrugations 15 extending along the entire length of the disrupter 5" so that the section of this disrupter is present. a plurality of sinuosities or meanders terminated at both ends by the C 11 return. It will of course be possible to provide, in particular, a disrupter combining the shapes and characteristics of the disturbers 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 disruptors 5, 5 'and 5 "are centered with respect to the tubes 4 at high pressure, the sealing at the boxes is ensured by the low pressure blade head and the high pressure tube.The use of these 30 disrupters avoids the problem of porosity between the high and low pressure tubes.

Claims (10)

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 low pressure refrigerant, 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 (li).   3. internal heat exchanger (3) according to claim 2, characterized in that said closure means (11) consist of raised side portions extending said disrupter (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 casing (9) reported, for (in) closing laterally ducts / low pressure passes.   An internal heat exchanger according to any one of the preceding claims, characterized in that the disruptor (5, 5 'or 5 ") has a plurality of localized protuberances (14), extending from its face flat internal (12).   7. Internal heat exchanger (3) according to any one of the preceding claims, characterized in that the disturbance (5) comprises corrugations extending over the entire length of the disturbance (5, 5 'or 5 ")   8. Internal heat exchanger (3) according to any one of the preceding claims, characterized in. said means consist of a plurality of disturbers (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.