Collection chamber for a heat exchanger, connection system and heat exchanger

Abstract

A plenum chamber (1) for an evaporator of an air conditioning circuit, designed to operate at an operating pressure of more than 120 bar, the evaporator being provided with tubes oriented in a main direction, the plenum chamber (1) comprising a cover (3) and a distributor plate (5) produced by punching and deep-drawing sheet metal, as well as a fluid inlet and a fluid outlet nozzle extending substantially perpendicular to the main direction, characterized in that the cover (3) and the distributor plate (5) each have a material thickness greater than or equal to 1 mm and each have a section with a substantially semi-cylindrical shape (19, 21) forming fluid inlet and fluid outlet nozzles.

Description

The present invention relates to the technical field of heat exchangers for motor vehicles. More particularly, the invention relates to a collection chamber of a heat exchanger, such as an evaporator of an air conditioning circuit, through which a supercritical state refrigerant, such as CO 2, flows, to a connection system and to a heat exchanger.Such a collecting chamber must thus be adapted to withstand a particularly high operating pressure, which can reach up to 150 bar. To ensure the reliability of the collection chamber, it must be designed to withstand a pressure at least three times as high as the operating pressure. It will thus be understood that the various elements of the circuit and in particular of the collecting chamber must have a particularly high mechanical strength.From document FR 2 923 902 A1 a collecting chamber for a heat exchanger is already known, which contains an arrangement of plates arranged one above the other, which are provided with openings for receiving heat exchanger tubes. Such a collecting chamber can contain in particular:a collecting plate,a distributor plate,a cover formed of an intermediate plate and a cover plate.The various plates of such a collection chamber are made by punching and deep drawing, thereby allowing them to withstand high pressures. However, such a collection chamber can be further improved. In particular, the collecting chamber of the prior art has a shape not designed to communicate with medium inlet and outlet ports provided according to a so-called "end-to-end" arrangement. By "end-to-end" arrangement is meant that the fluid inlet and outlet ports are substantially aligned with the longitudinal direction of the plenum chamber, with the axis of the ports being substantially perpendicular to the axes of the heat exchanger tubes. In contrast, in the known collecting chamber, the fluid inlet and outlet connections extend with their axes parallel to those of the tubes, since they are welded to the collecting chamber from below.Thus, with the collection chamber it is not possible to receive the inlet and fluid outlet ports in a so-called "end-to-end" arrangement.Also, the fact that the stubs cannot be provided in an "end-to-end" arrangement prevents the use in a large number of vehicles, in particular because of the space requirement.Also known from the document US 5 934 367 A is a collection chamber with a cover, a collection plate and an intermediate plate, in which collection chamber the stubs are placed in a so-called "side by side" arrangement. By "side-by-side" arrangement is meant that the inlet and fluid outlet ports are substantially perpendicular to a longitudinal direction of the plenum chamber, with their axis substantially perpendicular to the axes of the heat exchange tubes. Thus, in this document, the inlet and fluid outlet ports are part of the plates and the cover.However, in the type of collection chamber of the above-mentioned document US 5 934 367 A, the fluid pressure applied is ten times lower than in the collection chamber provided in the invention, particularly due to the cooling gases used at the time of disclosure of this document not being carbon dioxide (CO 2) in the supercritical state. The CO 2 was used in air conditioning circuits only from 2003 on the basis of a European environmental standard. In the publication U.S. Pat. No. 5,934,367 A, the cooling gas used is namely R134a which does not reach as high pressure values in an air-conditioning circuit.In this case, since the pressures are low, the inlet and outlet ports can be conveniently made of one piece with plates by forming them, since the plates forming these plates are very thin and hence easily formed.Documents EP 1 711 772 B1, DE 102 60 107 A1 and EP 2 726 808 B1 also describe heat exchangers for conventional refrigerants having a low fluid pressure.In heat exchangers subjected to an operating pressure of the order of 150 bar, such as those to which the invention relates and in which carbon dioxide flows, the collecting chamber must be particularly stable, and therefore plates made of a substantially thicker sheet must be provided. An increase in the thickness of the material of this sheet entails difficulties in forming in the home, particularly due to a risk of cracks and microcracks in the sheet at the time of deep drawing. This difficulty in forming--although well known to those skilled in the art--is all the more severe in forming pipe stubs in an "end-to-end" configuration.Furthermore, it is also undesirable from the outset to have too high hydraulic diameters because of the high operating pressure. Consequently, making inlet and outlet ports integrally bonded to the panels and covers themselves is a potential source of collection chamber leaks and chipping.Thus, it is not desirable from the outset to employ the deep drawing technique when it is desired to produce inlet and outlet stubs formed integrally with the plates of the collecting chamber when the respective pressure values are high, i.e. those which achieve CO 2 in the supercritical state.It is therefore proposed in WO 2006 / 129598 A1, as can be seen in FIG. 5, to form inlet and outlet each having a rectangular cross section by planar extensions of plates spaced apart from one another. According to the proposal, a solid connection block made of metal is in turn soldered onto these extensions. This is necessary, on the one hand, to give the connections the necessary compressive strength and, on the other hand, to enable the connection of pressure-resistant pipes or hoses with a usually round cross section. The massive connection block is, however, comparatively heavy and expensive to produce.The present inventors have found another surprising solution which is contrary to the above findings. The novel and inventive idea of the invention is to transfer a technique for manufacturing a heat exchanger operating at low pressure (below 15 bar) to the technical field of high operating pressure (close to 150 bar) heat exchangers and adapt it without going on the existing concerns.The invention thus aims to eliminate the aforementioned drawbacks by providing a collection chamber adapted to operate at an operating pressure of above 120 bar and having its pipe stubs provided according to the "end-to-end" arrangement.To this end, the invention proposes a plenum chamber for an evaporator of an air conditioning circuit provided with tubes oriented in a main direction, said plenum chamber comprising a cover and a distributor plate made by punching and deep drawing sheets, and a fluid inlet and a fluid outlet connection extending substantially perpendicular to said main direction, characterized in that said cover and said distributor plate each have a thickness of material greater than or equal to 1 mm and each have a portion having a substantially semi-cylindrical shape forming inlet and outlet connections.The collection chamber may further include one or more of the following features taken alone or in combination:The cover is in turn formed from two plates, namely an intermediate plate and a cover plate. The invention is particularly advantageous in this embodiment, since the production of the cover by stacking cut and deep-drawn plates creates a cover which is resistant to high pressure values.The intermediate plate is a metal sheet which has cut-outs in its material thickness at one of its ends, which cut-outs open out at one end of the intermediate plate and allow fluid to pass through in the material thickness of the intermediate plate. With these cut-outs, the passage of coolant in the region of inlet and outlet of coolant into the evaporator is optimized.The intermediate plate has longitudinal passages defined by walls, the end of which has a portion of inlet and outlet ports, and which form the fluid circuits in the collection chamber.The cover plate has parallel, semi-cylindrical shapes at one end of the cover, and the semi-cylindrical shapes of the cover plate lie opposite respective cut-outs of the intermediate plate, which are embodied in terms of their material thickness and open out at one end of the intermediate plate. These semi-cylindrical shapes and these cut-outs form portions of the fluid inlet port and the fluid outlet port which are particularly durable and have the advantage of being aligned in the "end-to-end" arrangement.the cover plate has longitudinal protrusions extending to near its end, and the longitudinal protrusions of the cover plate are opposed to respective longitudinal passages of the intermediate plate. The longitudinal protrusions and passages form fluid circuit portions in the collection chamber that are particularly resistant to high fluid pressure levels.The intermediate plate is produced starting from two plates arranged one above the other, each plate arranged one above the other preferably having a material thickness of at least 1.5 mm. An intermediate plate with a relatively large material thickness can thus be formed and the advantages of deep-drawing and / or punching out plates with a limited material thickness can be used in the process.The inlet and outlet nozzles are each surrounded by a shoulder which completes their formation and holds the panelsThis is a factor which contributes towards one another, at least until the plates are welded together.The invention also relates to a collection chamber as described above, which is designed to withstand a pressure of more than 350 bar equal to the test pressure, which is three times the operating pressure of the heat exchanger.The invention also relates to a connection system for an evaporator of an air conditioning circuit, comprising a collecting chamber as described above and a collecting plate with means for crimping a cover, said crimping means extending as far as the fluid inlet and the fluid outlet connection piece. As a result, due to the crimping means reaching the end of the connecting region, this pressure-sensitive region is stiffened.In an advantageous embodiment, the collecting chamber has recesses for allowing the semicylindrical shapes of the distributor plate to pass through.Finally, the subject matter of the invention is a heat exchanger with a collecting chamber as described above.The invention will be better understood from reading the accompanying figures, which are given by way of example and not by way of limitation, in which:FIG. 1 is an exploded perspective view of a collection chamber according to the invention;FIG. 2 is a perspective view of the collection chamber from FIG. 1.Referring to FIG. 1, there is shown a collection chamber 1 according to the invention intended to be mounted on a cooling circuit of a heat exchanger of the evaporator type of an air-conditioning circuit. The evaporator is flushed by a refrigerant in the supercritical state, such as carbon dioxide (CO 2), whose pressure can reach values above 150 bar.The evaporator (not shown) includes parallel tubes (not shown) aligned in a major direction referred to as a vertical direction, since such tubes often extend in a vertical direction when the evaporator is in a normal use position.The collecting chamber 1 contains in particular a cover 3 and a distributor plate 5, which are produced by deep drawing of aluminium sheets.The distributor plate 5 is formed from a deep-drawn aluminum sheet, the material thickness of which is between 1 mm and 1.5 mm.The cover 3 is in turn formed of two plates, namely an intermediate plate 7 and a cover plate 9, both of which are obtained by deep drawing of sheets having a thickness of between 1 mm and 1.5 mm.The intermediate plate 7 made of aluminium is obtained by cutting an aluminium sheet to size and has at one of its ends two cut-outs which allow an optimized flow of coolant in the region of the inflow and outflow of the coolant into the evaporator. These details are described in more detail in the following description.In addition to these components, the collecting chamber also contains a collecting plate 11 which is also obtained by deep drawing from an aluminium sheet whose material thickness is between 1 mm and 1.5 mm.The material thickness of the sheet metal from which each part is made is the material thickness of this part.Each of these plates has a generally rectangular shape.The cover 3 can be viewed as a unit of two halves separated in the middle 12 of the cover.Each longitudinal half of the cover contains:on the cover plate 9 four longitudinal protrusions 13 which extend from the middle 12 of the cover to the vicinity of its end in the example described, but without being limited thereto;on the intermediate plate 7: four longitudinal passages 15 which, in the example described, are separated, but not by way of limitation, by a transverse wall extending substantially in the region of the centre 12 of the cover.The longitudinal protrusions 13 are each located opposite the longitudinal feedthroughs 15.On one half of the cover (on the left in the figures), the longitudinal passages 15 of the intermediate plate 7 meet in pairs adjacent to the end of the cover to form two passages 17 which are open at the end of the plate and form the two aforesaid cut-outs. These cut-outs are bounded by the walls 18.On this same half of the cover, the cover plate 9 comprises, at the end of the cover, two parallel, semi-cylindrical shapes 19, each semi-cylindrical shape 19 being situated in the extension of the two adjacent protuberances 13.The half-cylindrical shapes 19 are each opposite the open passages 17, so that the cover, after the intermediate plate 7 and cover plate 9 have been joined together, forms four fluid circuits: two per cover half. On the left half of the cover (with reference to the figures), each fluid circuit communicates with one of the passages 17 open at the end of the cover.Thus, the cover formed of two plates can be considered to be a part obtained by punching and drawing sheets and comprising two semi-cylindrical shapes at one of its ends.The distributor plate 5 contains:substantially on its half-surface, for example on the left in relation to the figures, two rows 20a of elongated openings intended to join pipes running parallel and vertical (not shown perpendicular to the figure), as is known;substantially on its other half-surface, for example on the right in the figures, a single row 20b of oblong orifices intended to be connected to pipes running parallel and vertical (not shown) and intended to distribute the coolant;at one of its ends (on the left in relation to the figures), two semi-cylindrical shapes 21 symmetrical to the semi-cylindrical shapes 19 of the cover plate 9.The semi-cylindrical shapes of the cover plate 9 and the distributor plate 5 form portions of stubs, as well as the walls of the intermediate plate 7.Thus, the assembly consisting of the cover 3, in turn as a result of the joining of the cover plate 9 and the intermediate plate 7 and the distributor plate 5, is a collecting chamber having an inlet and an outlet stub formed from the stack of the semi-cylindrical shapes 19, 21 and the walls 18.These stubs extend substantially perpendicular to the vertical direction. They are thus provided in an "end-to-end" arrangement. With this arrangement of the nozzles, it is avoided to have to resort to an attached connector block in order to be able to use them on most vehicles and it allows to withstand high operating pressures compatible with the use of carbon dioxide maintained in the supercritical state by a pressure of 150 bar, due to the strength of the nozzles resulting from their construction.Next, the connectors 25 are attached to the connectors thus obtained.The collector plate 11 is also obtained by drawing an aluminium sheet and, as is known per se, has a crimping function which reaches as far as the end of the connection portion and thus allows to stiffen this high pressure sensitive portion.Furthermore, the collector plate has two recesses 23 intended to allow the passage of the semi-cylindrical shapes 21 projecting from the distributor plate 5. This makes it possible to ensure the crimping function of the collecting plate until the end of the tube forms.The collecting plate 11 also has rims 27 forming crimping means for crimping a cover (not shown) which extend up to the recesses 23 and thus up to the fluid inlet and outlet ports of the collecting chamber after manufacture thereof, which helps to stiffen the chamber in this particularly sensitive area.The invention is not limited to the illustrated embodiments, and other embodiments can be devised by those skilled in the art.In particular, the intermediate plate 7 can be produced from two plates arranged one above the other, wherein each plate arranged one above the other preferably has a material thickness of at least 1.5 mm.Furthermore, the number of plates, stubs, elevations, feedthroughs, sections and further quantities in the example described above is not a limitation at all.

Claims

A plenum chamber (1) for an evaporator of an air conditioning circuit, adapted to operate at an operating pressure of above 120 bar, said evaporator being provided with tubes oriented in a main direction, said plenum chamber (1) comprising a cover (3) and a distributor plate (5) made by punching and deep drawing sheets, as well as a fluid inlet and a fluid outlet stub running substantially perpendicular to said main direction, characterized in that said cover (3) and said distributor plate (5) each have a thickness of material greater than or equal to 1 mm and each have a portion with a substantially semi-cylindrical shape (19, 21) forming fluid inlet and fluid outlet stubs.Collection chamber (1) according to the preceding claim, wherein the cover (3) is in turn formed from two plates, namely an intermediate plate (7) and a cover plate (9).Collecting chamber (1) according to Claim 2, wherein the intermediate plate (7) consists of a metal sheet which has, at one of its ends, cut-outs in its material thickness, which open out at one end of the intermediate plate (7) and allow fluid to pass through in the material thickness of the intermediate plate (7).Collection chamber (1) according to claim 3, wherein the intermediate plate (7) comprises longitudinal passages (15) delimited by walls (18), the end of which comprises a portion of fluid inlet and outlet pipes.Collecting chamber (1) according to one of Claims 3 and 4, wherein the cover plate (9) has parallel, semicylindrical shapes (19) at one end of the cover (3), and the semicylindrical shapes (19) of the cover plate (9) are opposite respective cutouts of the intermediate plate (7) which are designed in terms of their material thickness and open out at one end of the intermediate plate (7).Collection chamber (1) according to any one of claims 4 and 5, wherein the cover plate (9) has longitudinal protrusions (13), which extend as far as the vicinity of its end, and the longitudinal protrusions (13) of the cover plate (9) are opposite respective longitudinal feedthroughs (15) of the intermediate plate (7).Collecting chamber (1) according to one of Claims 2 - 6, wherein the intermediate plate (7) is produced starting from two plates arranged one above the other, wherein each plate arranged one above the other preferably has a material thickness of at least 1.5 mm.Collection chamber (1) according to one of the preceding claims, wherein the fluid inlet and the fluid outlet connection are each surrounded by a shoulder piece (25).Collection chamber (1) according to any one of the preceding claims, designed to withstand a pressure of more than 350 bar equal to the test pressure three times the operating pressure.Connection system for an evaporator of an air conditioning circuit, comprising a collection chamber (1) according to one of the preceding claims and a collection plate (11) with means for crimping a cover (3), these crimping means extending as far as the fluid inlet and outlet connection pieces.The connection system according to the preceding claim, wherein the collecting plate (11) has recesses (23) for allowing the passage of the semi-cylindrical shapes (21) of the distribution plate (5).Heat exchanger with a collecting chamber (1) according to one of Claims 1 to 9.

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