FR2855602A1 - PLATE HEAT EXCHANGER, IN PARTICULAR COOLER FOR RECIRCULATED EXHAUST GASES - Google Patents

Abstract

The heat exchanger for the heat exchange between gases to be cooled and a coolant comprises a heat exchange bundle (2) constituted by a stack of plates (8, 10, 12) determining between them channels for the circulation of the gases to be cooled and for the channels for circulation of the coolant. Each circulation channel of the gas to be cooled is between two circulation channels of the coolant. Thus, the walls of the envelope which surround the heat exchange bundle (2) are cooled by the coolant. Application to the cooling of exhaust gases from motor vehicle engines.

Description

Plate heat exchanger, especially cooler for

recirculated exhaust gases.

  The invention relates to a heat exchanger for the heat exchange between gases to be cooled and a coolant, comprising a heat exchange bundle constituted by a stack of plates determining between them channels for circulation of the gases to be cooled. cool and coolant circulation channels.

  On a number of internal combustion engines, in particular on supercharged diesel engines, the pollution standards require recycling or recirculation of part of the exhaust gases. Before being mixed with the fresh combustion gases, the recirculated exhaust gases, the temperature of which can reach 500 C, must be cooled.

  This cooling is obtained by means of a heat exchanger, called a recirculating gas cooling exchanger. Known exchangers of this type are generally made of stainless steel. They comprise a bundle 25 made up of spacers and plates provided with an outer rim designed to seal the exhaust gases. Gas inlet and outlet manifolds are brazed at the ends of the heat exchange bundle.

  These known coolers have several drawbacks.

  The inlet and outlet manifolds consist of separate parts which must be assembled by soldering. This requires excess material and results in additional bulk. On the other hand, the walls of the shell of the exchanger, which are in contact with the exhaust gases, are at a very high temperature. They must therefore be made of a noble material such as stainless steel, which is expensive and which is difficult to shape.

  The subject of the invention is a heat exchanger, in particular a cooler for recirculated exhaust gases, which overcomes these drawbacks.

  These goals are achieved by the fact that each circulation channel of the gases to be cooled is between two circulation channels of the coolant.

  Preferably, the heat exchange bundle is surrounded by a casing comprising a first end wall contiguous to a first end plate of the bundle and a second end wall contiguous to a second end plate of the bundle, each end wall of the envelope defining a coolant circulation channel with the bundle end plate with which it is associated.

  Thanks to this characteristic, the envelope of the heat exchanger is in contact with the coolant. It is protected from direct contact with the exhaust gases and its temperature is considerably lowered. It can therefore be made of an inexpensive and easy to work material such as an aluminum alloy. If necessary, the walls in contact with the gases are treated to resist corrosion.

  In a preferred embodiment, the bundle plates are stamped plates so as to have a cavity delimited by a flange, these plates being grouped in pairs 30 and assembled by their flanges to define the channels for circulation of the coolant, with the exception of the first and second end plates which are joined by their edges respectively to the first and to the second end wall of the casing to form with each of them a coolant circulation channel .

  This characteristic makes it possible to produce a very flat, space-saving heat exchanger which can be easily mounted on another exchanger, for example a cooler for the engine charge air.

  Advantageously, the plates have ribs which delimit the circulation passages for the coolant and / or disturbing elements.

  In a particular embodiment, each plate comprises a stamped boss in which is cut an opening for circulation of the coolant, the bosses of a pair of plates being supported respectively on the bosses of the pairs of adjacent plates.

  These bosses thus delimit spaces between the surfaces 15 of the plates in which the gases to be cooled can circulate. A secondary exchange surface or a disturbing element, for example a corrugated interlayer, can advantageously be placed in the gas circulation channels to be cooled.

  However, at each end of the exchanger, the end plates are associated with the walls of the casing.

  Generally, the first and second end walls of the envelope have the general shape of a rectangle.

  Advantageously, the inlet manifold and the outlet manifold for the coolant are located on the same end wall of the envelope and along the same side of the rectangle, in particular the short side of this rectangle.

  Thus, the coolant supply and discharge pipes are close to each other. This arrangement facilitates their installation and reduces the size.

  Advantageously also, the inlet flange and the outlet flange of the gases to be cooled are situated on the same end wall as the inlet and outlet pipes for the coolant. In this way, all the connections are located on the same side of the exchanger.

  The shell of the exchanger can be produced in many different ways.

  In a preferred embodiment, at least one of the end walls has a peripheral rim which envelops, at least partially, the heat exchange bundle of the exchanger so as to constitute a casing.

  Each end wall can thus constitute a half-casing, these two half-casings being connected according to a joint plane situated halfway up the heat exchange bundle. Alternatively, one of the plates may constitute a complete casing closed by a flat end plate.

  The envelope delimits free spaces on either side of the gas circulation channels to be cooled in order to constitute inlet and outlet manifolds for these gases.

  The gas inlet and outlet flanges are connected to the enclosure at the level of the free spaces. Thus, there is no need to make and report separate inlet and outlet manifolds. The construction of the exchanger is simplified.

  Other characteristics and advantages of the invention will become apparent on reading the following description of exemplary embodiments given by way of illustration, with reference to the appended figures. In these figures: - Figure 1 is an exploded perspective view of a plate heat exchanger according to the invention; - Figure 2 is a top view of the heat exchanger of Figure 1; - Figure 3 is a partial sectional view on an enlarged scale along the line III-III of Figure 2; and - Figure 4 is a partial sectional view on an enlarged scale along the line IV-IV of Figure 2.

  The heat exchanger shown in Figures 1 to 4 is a cooler of recirculated exhaust gases from an internal combustion engine of a motor vehicle. In fact, the temperature of these gases is high and can reach 500 ° C. when they exit the engine. It is therefore necessary to cool them before re-mixing them with the fresh gases admitted into the combustion chambers. This cooling is carried out by heat exchange with a coolant, generally brine.

  The cooler comprises two main parts, namely a heat exchange bundle, designated by the general reference 2, and an envelope which surrounds the bundle 2. In the example, the envelope consists of two half-casings, namely an upper half-casing 6 and a lower half-casing 7.

  The bundle 2 consists of a stack of plates of generally elongated rectangular shape. In the example, it comprises four plates, namely an upper end plate 8, a lower end plate 10 and two common plates 12 matched to each other. Each plate has a bottom wall 14 and a peripheral flange 16 30 which defines with the bottom 14 a cavity in which the coolant circulates. Preferably, ribs 18 are formed in the bottom wall in order to determine passes for the circulation of the coolant.

  In the example, each plate has three ribs which determine four passes (that is to say two round trips) for the coolant. In addition, each plate may include disturbing elements, such as projecting reliefs, intended to disturb the flow of the coolant and to improve the heat exchange. In addition, each plate has a boss (see FIG. 3) located opposite the flange 16 and the ribs 18.

  An opening 22 is provided in the bottom wall of each boss 20 for the passage of the coolant.

  The upper half-casing 6 has a flat end wall 24 surrounded by a peripheral rim 26. Likewise, the lower half-casing 7 has a bottom end wall 10 surrounded by a peripheral rim 30. As can be seen, see in particular in FIG. 3, the peripheral rim 26 of the upper half-casing and the peripheral rim 30 of the lower half-casing meet along a joint plane so as to constitute a sealed envelope 15 which entirely contains the bundle 2 of the exchanger. The dimensions of the peripheral flanges 26 and 30 are determined in such a way that, when the two half-carters are assembled, the upper end wall 24 of the upper half-casing bears on the peripheral flange 20 than 16 of the upper end plate and, in the same way, the end wall 28 of the lower half-casing 7 comes to bear on the peripheral rim 16 of the lower end plate 10.

  In addition, each of the half-casings 6 and 7 comprises fixing lugs 31 which make it possible to mount the cooler of the exhaust gases on a structure. An inlet pipe 32 and an outlet pipe 34 for the coolant are provided on the upper half-casing. In example 30 ple, these two pipes are arranged along a short side of the upper half-casing, but other embodiments are possible. The upper half-casing 6 also includes a flange 36 and a flange 38 allowing the connection of a pipe for supplying the gases to be cooled and the evacuation of these gases. These flanges are fixed to collars 39 formed by stamping in the sheet metal constituting the upper half-casing. Thus, in the example, the coolant and gas pipes are all arranged on the same side of the exchanger, which facilitates their connection.

  As can be seen in particular in FIG. 3, the upper end plate 8 of the exchanger is assembled by its peripheral rim 16 to the end wall 24 of the upper half-casing 6. Thus, between these two 5 walls, a circulation channel 40 of the coolant. Likewise, the lower end plate 10 is assembled by its peripheral rim 16 to the end wall 30 of the lower half-casing 7 so as to delimit a circulation channel 40 of the coolant. The two current or generic plates 12 are assembled to each other by their peripheral edges 16 so as to delimit between their bottom wall 14 a circulation channel 42 for the coolant.

  Since, in this case, the coolant circulation channel is delimited by the superposition of two plates, its height is twice that of the circulation channels 40. The boss 20 of one of the plates 12 comes into support with the boss 20 of the upper end plate 8, while the boss of the other plate 12 comes to bear on the boss 20 of the lower end plate 10. The example shown has only two plates generic, but it goes without saying that it could include more, it being understood that these plates are matched.

  The openings 22 made in the different bosses are in coincidence with each other in order to allow the circulation of the coolant. Simultaneously, the bosses 20 determine a spacing between the bottom walls 14 of each of the plates 8, 10 and 12. Preferably secondary exchange surfaces 46, or disturbing elements, constituted for example by corrugated spacers, are arranged in the circulation channels 44 of the 35 gases to be cooled. The height of each channel is twice the height of a boss 20.

  According to the invention, each channel 44 for circulation of the gases to be cooled is between two circulation channels i. 2855602 tion of coolant. The cooler shown in the example comprises two circulation channels 44 each surrounded, respectively, by a channel 40 and by the central channel 42. Thanks to this characteristic, the upper half-casing 6 and the lower half-casing 7, and in particular the bottom walls 24 and 28 of these half-casings are not in contact with the gases to be cooled. On the contrary, the walls 24 and 28 are cooled by the circulation of the coolant in the channels 40. The temperature 10 of the walls 24 and 28 is thus considerably lowered compared to the temperature of the end walls of a conventional exchanger. It can for example be of the order of 200 C. These walls can therefore be made of a material which is less resistant to temperature, such as aluminum. This advantage is appreciable because aluminum is easier to work and costs less than stainless steel.

  The general shape of the half-casings 6 and 7 corresponds to the shape of the beam plates. However, the half-casings have extensions 48 located on either side of the elongated sides of the plates of the exchanger. In this way, free spaces are defined on either side of the inlet and the outlet of the channels 44 for circulation of the gases to be cooled. These free spaces make it possible respectively to constitute an inlet manifold box and an outlet manifold box for the exhaust gases. They extend over the entire length of the plates, and particularly over the entire length of the channels 44. In the example, the extensions 48 have a very flat triangle shape. It goes without saying that they could have other shapes, for example a substantially rectangular shape. The fixing flanges 36 and 38 intended respectively for fixing a supply pipe and a pipe 35 for discharging the gases to be cooled are arranged on the extensions 48 of the upper casing 6. However, in an alternative embodiment, a flange 36 could be arranged on a half-casing, while the other flange 38 would be disposed on the other half-casing.

  Thanks to this characteristic, it is not necessary to produce separate manifolds for the gases, which must be assembled by brazing to the rest of the exchanger.

  Consequently, material is saved and the number of operations necessary for manufacturing the exchanger is reduced.

  The exhaust gas cooler which has just been described has a very planar shape, in particular because of the small number of plates which it comprises. It takes up little space and can be easily attached to another exchanger, for example a charge air cooler.

Claims (10)

claims   1. Heat exchanger for the heat exchange between gases to be cooled and a coolant, comprising a heat exchange bundle (2) constituted by a stack of plates (8, 10, 12) determining between them channels (44) for circulation of the gases to be cooled and channels (40, 42) for circulation of the coolant, characterized in that each channel (44) for circulation of the gas to be cooled is between two channels (40, 42) for circulating the coolant.   2. Exchanger according to claim 1, characterized in that the bundle (2) is surrounded by an envelope comprising a first end wall (24) attached to a first end plate (8) of the bundle and a second end wall (28) attached to a second end plate (10) of the bundle (2), each end wall (24, 28) defining a channel (40) for circulation of the coolant with the end plate (8, 10) with which it is associated.   3. Heat exchanger according to one of claims 1 and 2, characterized in that the plates (8, 10, 12) are stamped plates so as to comprise a cavity delimited by a flange (16), these plates being grouped in pairs and joined by their edges (16) to define channels (42) for circulation of the coolant, with the exception of the first and second end plates (8, 30 10) which are assembled by their edges (16) respectively at the first and at the second end wall (24, 28) of the envelope to form with it a channel (40) for circulation of the fluid to be cooled.   4. Heat exchanger according to one of claims 1 to 3, characterized in that the plates have ribs (18) which delimit the circulation passages of the coolant and / or disturbing elements.   5. Heat exchanger according to one of claims 1 to 4, characterized in that each plate has a stamped boss (20) in which is cut an opening (22) for circulation of the coolant, the bosses (20) 5 a pair of plates (12) being supported respectively on the bosses of the pairs of adjacent plates.   6. Heat exchanger according to one of claims 1 to 5, characterized in that the first and second end walls (24, 28) of the envelope have the general shape of a rectangle and in that 'It comprises an inlet pipe (32) and an outlet pipe (34) of the coolant located on the same end wall (24) of the envelope and along the same side of the rectangle. 15 7. Heat exchanger according to claim 6, characterized in that the inlet pipe (32) and the outlet pipe (34) of the coolant are located along a small side of the rectangle. 20 8. Exchanger according to one of claims 6 or 7, characterized in that it comprises an inlet flange (36) and an outlet flange (38) of the gases to be cooled located on the same end wall (24 ) that the inlet and outlet pipes (32, 34) of the coolant.   9. Exchanger according to one of claims 1 to 8, characterized in that at least one of the end walls (24, 28) comprises a peripheral rim (26) which at least partially envelops the bundle (2) heat exchange so as to constitute a casing.   10. Heat exchanger according to one of claims 1 to 9, characterized in that the envelope delimits free spaces on either side of the channels (44) for circulation of the gases to be cooled in order to form manifolds inlet and outlet for these gases.