FR2920045A1 - MULTI-FLAP EVAPORATOR, ESPECIALLY FOR A MOTOR VEHICLE AIR CONDITIONING CIRCUIT - Google Patents

Abstract

An evaporator (10) comprises an evaporator core (12) comprising at least first and second superposed layers (42, 44, 46) extending in parallel planes, each being formed of a series of tubes or plates traversed by a refrigerant to be evaporated, so as to cool an air flow (28) passing through the planes of the layers (42, 44, 46). Dispensing means are connected to an inlet (24) and a fluid outlet (26) and define a flow of the fluid in a given direction for each conduit. An additional ply (18) is disposed adjacent to the evaporator core (12) and receives the fluid circulating in the evaporator core (12) to deliver it to the fluid outlet (26). The evaporator is particularly suitable for refrigerants consisting of mixtures, azeotropic or zeotropic, of different fluids.

Description

Multilayer evaporator, in particular for a circuit of

  automotive air conditioning

  The invention relates to evaporators, in particular those used in motor vehicle air conditioning circuits.

  It more specifically concerns those evaporators which comprise several superposed layers of refrigerant fluid lines.

  The basic structure of such an evaporator comprises, on the one hand, a core usually consisting of two plies of parallel refrigerant pipes and, on the other hand, fluid distributing means arranged at both ends of these plies for ensure the distribution and collection of the refrigerant in the different pipes of each of the layers.

  The pipes are made from individual heat exchange plates configured to define the flow of the fluid, or from individual tubes joined at both ends by manifold boxes whose internal structure determines the differences between them. refrigerant circulation passes, for example by means of intermediate partitions provided in these boxes and insulating subgroups of fluid lines of a web.

  The distribution means (configuration of the plates or internal partitioning of the collector boxes) can be designed to allow a circulation in several passes, with reversal of one pass to the next. The flow diagram may comprise, for at least some of the plies, partial paths in opposite directions, and / or paths in opposite directions from one ply to the other, constituting exchangers of the so-called "counter-flow" type or cross currents ".

  A flow of air passes through the intervals between the fluid lines, and this air gives way to the refrigerant, which changes from the liquid state to the gaseous state. The air flow thus refrigerated can be used in particular for the air conditioning of the passenger compartment of a vehicle.

  Such evaporators are for example disclosed in US-A-2006/0185386 or JP-A-2006/029697. These documents describe two-ply exchangers with a plurality of different fluid paths, so as to define in parts of each ply, and / or from one ply to the other, a fluid path along U-shaped circuits. / or with cross flows.

  EP-A-0 912 869 and DE-A-4446817 also disclose two-ply evaporators with other refrigerant circulation configurations.

  The development of new exchangers, particularly in the automotive field, leads to the design of reduced mass equipment, nevertheless having excellent cooling performance and energy efficiency.

  The latter is evaluated by the "coefficient of performance" or COP, which is the ratio between the heat energy (enthalpy) exchanged and the energy consumed by the system.

  A first problem to be solved is that of improving the heat exchange between the refrigerant and the air to be cooled.

  This improvement involves maximizing the temperature difference between the incident air and the cooled air after passing through the evaporator. It is also necessary to maintain a good homogeneity of temperature between the different regions (right / left, up / down) of the exchanger, which implies controlling the evaporation process, particularly from the point of view of the distribution of pressure losses within the various regions of the evaporator.

  One of the aims of the invention is thus to design a multiple-pass evaporator defining for the refrigerant fluid a path that optimizes the different passes relative to each other and improves evaporation. In addition to these constraints, there is a new difficulty stemming from recent regulations banning the use of certain refrigerants, particularly chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), in various sectors such as vehicle air-conditioning. automobiles.

  Research on possible substitution fluids has focused on the use of mixtures of several refrigerants. However, the use of mixtures in place of pure fluids must take into account the behavior of these evaporation mixtures, which may be azeotropic (at constant pressure, the evaporation temperature is constant) or zeotropic (at constant pressure, the evaporation temperature increases).

  The invention also applies to currently used fluids such as R-134a (1,1,1,2-tetrafluoroethane of chemical formula CH2F-CF3) or R-744 (carbon dioxide of chemical formula CO2) which are pure bodies, azeotropes. In addition, concretely, the evaporation is never done at constant pressure but at decreasing pressure when the refrigerant flows in the exchanger, due to the singular pressure losses and pressure losses in the tubes or in the plates. the exchanger. This always results in a "temperature shift" of the mixture. This phenomenon has the consequence that, for an azeotropic mixture, the temperature of the refrigerant decreases during the evaporation process whereas, conversely, for a zeotropic mixture, this temperature increases. The evaporator must therefore be adapted to the refrigerant used, if one wishes to optimize the performance. This adaptation will eventually have to take into account the zeotropic or azeotropic nature of the coolant, due to the different behavior during the evaporation process. To solve the above problems, the invention provides a multi-web type evaporator comprising: an evaporator core comprising at least first and second superimposed webs extending in planes, preferably parallel, each ply being formed of a series of parallel conduits traversed by a refrigerant fluid to be evaporated, so as to cool an air flow passing through the planes of the plies, in a particular embodiment in an incident direction directed substantially orthogonal to the planes of the plies and fluid distribution means disposed at both ends of the plies and connected to a fluid inlet and a fluid outlet, these distribution means being configured to ensure the distribution and collection of the fluid in the different pipes of each of the plies defining between the distributing means a circulation of the fluid in a direction of born for each driving.

  According to the invention, the evaporator comprises at least one additional layer disposed adjacent to the evaporator core, and cooperating with the distributor means so as to receive the fluid having circulated in the core and to deliver it to the fluid outlet. .

  According to an alternative embodiment, the additional ply is able to ensure overheating of the refrigerant. It is particularly advantageous from the upstream side to the evaporator core, that is to say on the side of the incident air flow.

  Preferably, the evaporator according to the present invention comprises altogether at least five layers. It may also include a smaller number, for example three, or a greater number, for example seven.

  Advantageously, at least a portion of the refrigerant flow path in the additional ply is a counterflow flow relative to the pass in the evaporator core.

  The distribution means may in particular be configured so as to define at least two different fluid passes in opposite directions in each of the first and second layers of the evaporator core.

  The splitter means are, moreover, configured so as to define a pass in one direction in the additional layer.

  In a first embodiment of the invention, the evaporator core comprises two layers, comprising a number of successive fluid passes which is greater than the number of passes of the second layer, so as to present, for each of the passes successive successive layers, total flow sections of the fluid decreasing from the first ply to the second ply, and the second ply to the additional ply.

  According to a specific example, the evaporator core comprises two plies, comprising a number of successive fluid paths which is greater in opposite directions to the number of paths of the second ply.

  In particular, the first web is located on the side of the fluid inlet connected to the fluid distributing means. To this end, the relative dimensions of the fluid pipes or fluid passages of the additional ply and the fluid passages or conduits of the evaporator core can be chosen so that the overall cross section of the pipes of the evaporator core can be selected in such a way that additional ply is less than the total overall section of the pipes of each of the plies of the evaporator core.

  In particular, the relative dimensions of the pipes of the additional ply and those of the evaporator core can be chosen so that the total overall section of the pipes of the additional ply is less than one-third of the total overall section of the plumes. pipelines of the evaporator core.

  In a second embodiment of the invention, the distribution means are configured to allow the refrigerant to enter the evaporator core layer adjacent to the additional layer, in particular facing an air inlet. and the transfer to the additional ply, after passing through the evaporator core, of the fluid coming from the ply situated opposite the additional ply, facing an air outlet.

  This second embodiment of the invention is particularly suitable for the case of an azeotropic refrigerant.

  In a third embodiment of the invention, the distribution means are configured so as to allow the refrigerant to enter the ply situated at the opposite of the additional ply, in particular in front of an air outlet. and the transfer to the additional layer, after passing through the evaporator core, of the fluid coming from the sheet located adjacent to the additional layer.

  This third embodiment of the invention is particularly suitable for the case of a refrigerant fluid of zeotropic type.

  However, the second and third embodiments can be alternately adapted to zeotropic or azeotropic refrigerants.

  In either case, the evaporator core may comprise three plies (so as to define in the evaporator assembly at least four different fluid paths in opposite directions), or five plies ( so as to define in the whole of the evaporator at least six different fluid paths in opposite directions), or even seven layers (so as to define in the whole of the evaporator at least eight fluid paths different in opposite directions).

  With regard to the technology, the evaporator of the invention can be made from: 25 or individual heat exchange plates defining parallel circulation blades successively traversed by the refrigerant fluid or from a series of crossed individual tubes by the refrigerant 30 corresponding to a respective pipe of each of successive layers of the evaporator core and the additional layer These plates or tubes are stacked alternately with intermediate fins traversed by the air flow.

  According to the embodiments, the distribution means are alternately formed by a configuration of the fluid circuit defined by each individual plate of the stack or by at least one defined collecting box joining the plates or tubes to at least one of the two ends. plates or tubes.

  Various embodiments of the present invention, given by way of example, will now be described with reference to the appended figures in which the same reference numerals designate, from one figure to another, identical or functionally identical elements. FIGS. 1 to 3 schematically illustrate, in perspective view, in plan view and in perspective, a first embodiment of the evaporator according to the present invention, FIG. 4 schematically illustrates, in side view, a second embodiment according to the present invention, FIG. 5 is a variant of the embodiment of FIG. 4, with an increased number of passes, where FIG. 6 schematically illustrates, in elevation, a third embodiment according to the present invention, FIG. 7 is a variant of the embodiment of FIG. 6, with an increased number of passes. FIGS. 8 and 9 illustrate two possible configurations of tubes, making it possible to produce a four-pass exchanger according to the second embodiment according to the present invention presented in FIG. 4; FIGS. 10 and 11 illustrate two possible configurations of tubes, making it possible to produce a four-pass exchanger according to the third embodiment according to the present invention presented in FIG. 6, in FIGS. 12a to 12c, illustrate three possible configurations of plates making it possible to produce a four-pass exchanger according to the second embodiment of FIG. Embodiment according to the present invention presented in FIG. 4, FIGS. 13a to 13d illustrate other possible configurations of plates, usable as a variant of the preceding ones, FIGS. 14a and 14b illustrate two possible configurations of plates making it possible to carry out an four-pass generator according to the third embodiment shown in FIG. FIGS. 15a to 15c illustrate three other possible configurations of plates, usable as an alternative to the preceding ones; FIG. 16 illustrates another possible configuration of plates, usable as an alternative to the preceding ones; FIGS. 17a and 17b illustrate two possible configurations of FIG. The plates making it possible to produce a six-pass heat exchanger according to the second embodiment of the present invention shown in FIG. 5, FIGS. 18a and 18b illustrate two possible configurations of plates making it possible to produce a heat exchanger. six passes according to the third embodiment of the invention presented in FIG.

  The various embodiments according to the present invention are particularly designed to optimize the pressure drops experienced by the refrigerant during the various passes of circulation in the evaporator, thus leading to a better control of the process of evaporation and a better homogeneity of the temperature of the refrigerated air.

  The configurations that will be described can be made from plates or tubes joined by collector boxes.

  Figures 1 to 3 illustrate an evaporator 10 having an evaporator core 12 itself comprising two superimposed plies 20 and 14, respectively a first and a second ply. This evaporator core 12 includes a number of passes equal to five. Evaporators known from the state of the art have configurations with four or six passes. Characteristically according to the invention, there is added to the evaporator core 12 an additional ply "18, or third ply, located upstream of the evaporator core 12, that is to say on the arrival side. The manifold 20 and 22 define a fluid path between an inlet 24 and a coolant outlet 26 and define means for distributing the coolant.

  According to alternative embodiments, the manifolds 20 and 22 are equivalently arranged by an appropriate configuration of the fluid flows at the ends of each of the plates.

  The first ply 14 is divided into three zones, so that the fluid arriving through the inlet 24 circulates in three successive passes, respectively a first pass 30, a second pass 32 and a third pass 34 with each time inversion of the direction of circulation. The fluid is then directed towards the second ply 16, which is divided into two zones so as to define a first pass 36 and a second pass 38. At the outlet of the ply 12, after the path 38, the fluid is directed towards the ply additional 18, that it crosses over its entire width along a single pass 40 to the outlet 26.

  According to a preferred embodiment, the first pass 36 of the second ply 16 is in the opposite direction of the third pass 34 of the first ply 14 and the second pass 38 of the second ply 16 is in the opposite direction of the first pass 36 of the second ply 36. tablecloth 16.

  During the evaporation process, the density of the cooling fluid decreases, and the described configuration makes it possible to compensate for this phenomenon by increasing the flow section of the first ply 14 to the second ply 16. This makes it possible to avoid an increase in pressure losses, keeping the heat exchange coefficient as constant as possible. In the first ply 14, the circulation in three passes makes it possible to increase the mass flow rate and therefore the heat exchange coefficient, while in the second ply 16 the circulation in two passes instead of three increases the section. flow, and consequently decreases the mass flow and reduces pressure drops.

  The additional ply 18 is a sheet of reheating of the fluid after the evaporation thereof. While in the evaporator core 12 (plies 14 and 16), the refrigerant fluid was essentially in the two-phase state (liquid / gas), in the additional ply 18 it can be in the two-phase state as well as in the two-phase state. the gaseous state, due to overheating (superheating phenomenon).

  The additional ply 18 has been defined with a single pass 40 to avoid temperature variations on one face of the evaporator. In particular, it avoids the right / left imbalance that could be problematic in particular for low thermal loads.

  With regard to the size of the plies, the width (transverse dimension) of the first and second naps 14 and 16 may be identical (as illustrated), but the width D2 of the additional ply 18 must be less than the width. total D1 of the first and second plies 14 and 16 of the evaporator core 12. The width D2 of the additional ply 18 has, for example, a value less than 1/3 that of the evaporator core 12. Thus, the total width D1 of the first and second plies 14 and 16 of the evaporator core 12 is greater than twice the width D2 of the additional ply 18.

  It will be appreciated that the additional ply 18 has been placed on the side of the air flow 28 to be cooled, to account for the rapid increase in temperature of the coolant at overheating. This makes it possible to optimize the heat exchange between the refrigerant and the air passing through the evaporator and, on the other hand, to reduce the differences in temperature of the air flow after passing through the evaporator 10.

  In general, the configuration just described provides better cooling performance, a better overall coefficient of performance (COP) of the system because the pressure is greater for the same temperature of the outlet air flow and a better homogeneity of the temperature.

  The evaporator according to the first embodiment which has just been described is usable both with zeotropic and azeotropic fluids.

  It will be noted, however, that the successive counter-flow circulations (passes 30/32, 32/34, 34/36, etc.) are particularly well suited for use with zeotropic mixtures having a temperature variation or slip. . They are however also suitable for azeotropic refrigerant fluids, in case of operation with significant overheating. From the point of view of technology, the evaporator can be made using plate or tube techniques.

  The use of a technology using tubes and associated collector boxes, however, has the advantage, because of the presence of the boxes at the end of each of the passes, to homogenize the liquid / vapor phases of the refrigerant before the next pass, the manifold then playing the role of mixing chamber. Indeed, a uniform distribution of the refrigerant at the inlet of each pass is generally desirable to properly distribute the liquid phase of refrigerant on the inner surface of the pipes and thus improve the heat exchange.

  Figures 4 and 5 illustrate a second embodiment of the invention, more particularly adapted to the use of azeotrope refrigerant fluid.

  In the case of the evaporator of FIG. 4, the evaporator core 12 comprises first, second and third plies, respectively, 42, 44 and 46 defining with the additional ply 18 a fluid path with four plies. In the case of Figure 5, the evaporator core 12 comprises two additional plies 48 and 50 defining with the additional ply 18 a six-ply path.

  The operation of the evaporator 10 of FIG. 4 is similar to the evaporator 10 of FIG. 5 and the following explanations apply to both cases.

  This configuration may be extrapolated to an evaporator core having a greater number of webs (e.g., eight or more webs), defining an increased number of passes for the fluid path. Preferably, the number of layers is even.

  For an azeotropic refrigerant (i.e. in which at constant pressure the evaporation temperature is constant), the temperature of the refrigerant decreases during the evaporation process. The difference is of the order of -1 C for 0.1 bar for a subcritical fluid, such as R-134a, and -1 C for 1 bar for the supercritical fluid, such as R-744. However, for high refrigerant mass flow rates, the pressure drops typically reach 1 to 2 bars for subcritical refrigerants, leading to a temperature drop of 10 to 20 C. For the R-744, the pressure drops reach 3 to 6 bar, leading to a temperature drop of 3 to 6 C.

  The configuration of the invention illustrated in FIG. 4 uses this variation (or slip) of temperature to optimize the performance of the evaporator.

  In FIG. 4, the curve 52 represents the evolution of the temperature in the evaporator core 12, where the coolant circulates successively in the three layers 46, 44 and 42, with each time inversion of direction.

  According to this variant embodiment, the fluid inlet is via the inlet 24 in the ply 46 which is the ply of the evaporator core 12 closest to the additional ply 18. The fluid flowing in the exchanger core 12 is essentially in the two-phase liquid / gas state. As illustrated in FIG. 4 along the curve 52, the temperature of the fluid gradually decreases from a To value (inlet temperature) to a temperature T1 (temperature at the outlet of the exchanger core 12, before recirculation in the slick additional 18).

  The fluid is then directed to the additional ply 18, which it passes through to the fluid outlet 26. As it passes through the additional ply 18, the fluid warms up, from the temperature T1 to a temperature T2, as indicated by the curve 54. In this additional ply 18, the fluid can be in the two-phase state or in the gaseous state, due to overheating.

  The curve 56 shows the temperature of the air passing through the evaporator 10, from an initial temperature T3, to the inlet into the evaporator 10 on the side of the additional ply 18, to a temperature T4, in leaving the evaporator 10 after passing through the successive layers 46, 44 and 42 of the evaporator core 12.

  It will be noted that the additional ply 18 has been placed on the side of the air inlet, since the temperature of the superheated refrigerant is increasing rapidly (curve 54). This position makes it possible to optimize the heat exchange between the refrigerant and the air flow, to reduce the temperature difference at the outlet of the evaporator and, consequently, to obtain better performances, a better efficiency. thermal, and more homogeneous temperatures.

  The configuration that has just been described makes it possible in particular to reduce the difference X between the temperature T4 of the cooled air flow after passing through the evaporator 10 and the temperature T1 of the refrigerant at the end of the evaporation process. This difference X (or pinching) is representative of the overall efficiency of the exchanger, that is to say, its ability to refrigerate the incident air flow.

  Figures 6 and 7 are homologous to Figures 4 and 5, for a third embodiment, more particularly adapted to the use of a zeotropic refrigerant fluid.

  In the case of the evaporator of FIG. 6, the evaporator core 12 comprises three plies 42, 44 and 46 defining with the additional ply 18 a four-ply fluid path. In the case of Figure 7, the evaporator core 12 comprises two additional plies 48 and 50 defining with the additional ply 18 a path to six plies. The operation of the evaporator 10 of Figure 7 is similar to the evaporator 10 of Figure 6 and the following explanations are valid for both cases.

  Again, this configuration can be extrapolated to an evaporator core 12 having a greater number of webs (e.g. eight or more webs if necessary), de-fining an increased number of passes for the fluid path. Preferably, the number of layers is even.

  It will be noted that, unlike the evaporators of FIGS. 4 and 5, in this third embodiment, the admission of fluid is via the inlet 24 in the ply 42, the ply of the evaporator core 12 furthest from the additional tablecloth 18.

  For a zeotrophic refrigerant fluid (i.e., where the temperature increases with constant evaporation pressure), the temperature of the refrigerant increases during the evaporation process. With the configuration illustrated in FIG. 6, this variation (or sliding) of temperature is used to optimize the performance of the evaporator 10.

  Curve 58 represents the evolution of the temperature of the refrigerant in the evaporator core 12, where the fluid flows successively in the plies 42, 44 and 46, with each time inversion of direction.

  The fluid flowing in the exchanger core 12 is essentially in the two-phase liquid / gas state. As illustrated by the curve 58, the fluid temperature increases progressively from a To value (inlet temperature) to a temperature T1 (temperature at the outlet of the sample core 12, before recirculation in the additional ply 18). .

  The fluid is then directed to the additional ply 18, which it passes through to the fluid outlet 26. When it passes through the additional ply 18, the fluid reheats again, from the temperature T1 to a temperature T2, as indicated by the curve 60. In this additional ply 18, the fluid can be in the two-phase state or in the gaseous state, because of its superheated state. Curve 56 shows the temperature of the air flow passing through the evaporator 10, from an initial temperature T3, to the inlet into the evaporator 10 on the side of the additional ply 18, up to a temperature T4 at the outlet of the evaporator 10 after passing through the successive layers 46, 44 and 42 of the evaporator core 12.

  The configuration just described makes it possible to obtain a lowering of the air temperature (T3-T4) of the same order as that which one would have with an azeotropic fluid (the case of FIG. 5), and also to reduce in comparable proportions the difference X (or pinching) between the temperature T4 of the cooled air flow after passing through the evaporator 10 and the temperature T1 of the refrigerant at the end of the evaporation process.

  Various ways of concretely obtaining the various configurations of evaporators which have just been described will now be described, by using the two techniques for producing heat exchangers, either from plates or from tubes. gathered by collecting boxes. This technique is illustrated in FIGS. 8 and 9, in the example of a four-pass exchanger according to the second embodiment of the invention shown in FIG. 4 comprising a series of tubes.

  It involves stacking a series of tubes alternately with fins, as for the plates. As illustrated in FIG. 8, each layer of tubes consists of separate tubes defining fluid paths for each of the layers 42, 44, 46 and 18. Alternatively, as illustrated in FIG. 9, each layer of tubes consists of a monobloc assembly incorporating several tubes.

  In order to ensure the circulation of the refrigerant between each tube, the ends of the tubes are mounted in collectors. Thus, the fluid enters an upstream collection chamber of the tube defining the sheet 46 and gains a downstream collection chamber of the latter which also constitutes an upstream collection chamber of the tube defining the sheet 44. The fluid then passes into a the downstream collection chamber of the latter before circulating in the tube defining the sheet 42. After having circulated therein, the fluid arrives in a final collection chamber which transfers the fluid to the tube carrying the sheet. addition-nelle 18. It then joins the coolant outlet.

  An alternative technique is illustrated in FIGS. 10 and 11, in the example of a four-pass exchanger according to the third embodiment of the invention shown in FIG. 6. Each layer of tubes is constituted either as illustrated in FIG. 10, separate tubes defining fluid paths for each of the plies 42, 44, 46 and 18, or, as illustrated in Figure 11, a one-piece assembly incorporating several tubes.

  As in the example of FIGS. 8 and 9, the refrigerant fluid transits alternately in collection chambers and in the tubes.

  According to the various embodiments described in FIGS. 8 to 11, the various collection chambers are arranged so as to form two unitary assemblies disposed respectively on either side of the tubes. These two unitary units define the manifolds 68 and 70 and are means for distributing the refrigerant fluid The manifolds 68 and 70 are each provided with appropriate internal partitions for communicating the ends of the tubes according to a predetermined flow diagram.

  According to a variant described, the manifold 70 is connected to the intake manifold and the coolant collection manifold. The layers of adjacent tubes are separated from each other by corrugated inserts defining flow passages of a flow of air between the corrugations of the spacers, so that the layers of individual circulation tubes of the refrigerant flowing through the beam alternate with circulation passages of the outside air flow. Figures 12a. at 12c illustrate, in a plate technology, three possible configurations of plates making it possible to produce a four-pass exchanger according to the second embodiment of the invention as described above with reference to FIG. 4.

  The exchanger is formed of a stack of identical plates, such as that illustrated in Figures 12a, 12b or 12c. Each of the plates delimits parallel circulation blades traversed successively by the refrigerant fluid and corresponding to a respective pipe of each of the successive layers 46, 44, 42 and 18, as defined in relation to FIG. comprises a fluid inlet 24 and a fluid outlet 26, as well as possibly passages 62, 64 and 66 for connecting between them, in selected regions, the different refrigerant circulation channels.

  The adjacent plates are separated from each other by corrugated inserts defining passageways for circulating an air flow between the corrugations of the spacers, so that the individual circulation plates of the refrigerant flowing through the beam alternate with passages of circulation of the outside air flow.

  As can be seen in the different variants of plate configurations illustrated in FIGS. 12a to 12c, each plate is arranged so that the cooling fluid circulates successively in the different circulation blades according to the configuration described above with reference to FIG. variants of Figures 8a to 8c, the presence of the passages 62 and / or 64 and / or 66 allows an intermediate mixing of the refrigerant during this path, which allows to reduce correlatively the size of the intermediate fins.

  FIGS. 13a to 13d illustrate another series of plate configurations, without intermediate mixing of the coolant. These configurations are adapted to larger wings. These variants differ in particular from the possibility of providing input and output lines 26 having different cross-sections, as shown in FIGS. 13b and 13c, possibly with respective circulation blades of different width. in particular, a greater width for the blade defining the additional ply 18 traversed by the fluid before the outlet 26. The variants of FIGS. 13c and 13d provide for a section that is no longer circular but oval for the entry 24 and / or the outlet 26 for fluid . These sections are adapted to intake manifolds or coolant collection having a corresponding section.

  The configurations of FIGS. 13c and 13d also differ from each other by the relative position of the inlet 24 and the outlet 26 of the refrigerant, which are brought together in the case of FIG. 13c and moved away in the case of FIG. 13d. to accommodate corresponding intake manifold and fluid collection configurations.

  FIGS. 14a and 14b illustrate two possible configurations of plates making it possible to produce a four-pass exchanger according to the third embodiment of the invention as described above with reference to FIG.

  The exchanger is formed of a stack of identical plates, such as that illustrated in FIGS. 12a to 12c. Each of the plates delimits parallel circulation blades successively traversed by the refrigerant fluid, and corresponding to a respective pipe of each of the successive layers 42, 44, 46 and 18, as described in relation with FIG. Each blade has a fluid inlet 24 and a fluid outlet 26, as well as optionally passages such as 62, 64, 66 for connecting the different refrigerant circulation channels with each other in selected regions. allow intermediate mixing of the refrigerant during its journey in the exchanger, which allows to reduce correspondingly the size of the intermediate fins separating the plates of the stack.

  Figures 15a to 15c illustrate another series of plate configurations, adapted to larger fins. These variants differ in particular in the possibility of providing an outlet duct 26 having a larger section, as the example of FIG. 15b, possibly with a larger width for the blade defining the additional ply 18 traversed by the fluid before the exit. fluid 26, or, in the example of Figure 15c, by the presence of a single passage 62 per-putting a stirring of the refrigerant halfway.

  The variant of Figure 16 allows to give oval sections at the inlet 24 and the outlet 26 of the refrigerant. These sections are adapted to intake manifolds or fluid collection having a corresponding section.

  FIGS. 17a and 17b illustrate two possible configurations of plates making it possible to produce a six-pass heat exchanger, corresponding to the second embodiment of the invention presented in FIG. 5. The plate configuration of FIG. 17a is derived from that of FIG. 13a, with two additional blades of fluid circulation. The plate configuration of Fig. 17b is derived in the same way from that of Fig. 13c.

  Figures 18a and 18b illustrate two possible configurations of plates for making a six-pass heat exchanger, corresponding to the third embodiment of the invention shown in Figure 7. The plate configuration of Figure 18a is derived from that of Figure 15a , with two additional fluid circulation blades. The plate configuration of Figure 18b is derived in the same way from that of Figure 16.

  In all the embodiments described above, it is possible to provide on the wall of the plates, in the region of the fluid circulation blades, reliefs in the form of ribs or bosses (or dimples), in order to provide better resistance to the pressure of the refrigerant circuit, and a better heat exchange between the refrigerant flowing on one side of the wall of the plate and the air flowing on the other side of the same wall.

  Depending on the heat exchange requirements within the heat exchanger and in order to obtain better cooling performance, a better overall COP and a better temperature homogeneity, it is possible to define a or several passes in the tablecloths.

  The present invention finds particular application in thermodynamic refrigerant circuits, including heating, ventilation and / or air conditioning and in particular in the field of automotive equipment.

  Obviously, the invention is not limited to the embodiments described above and provided solely by way of example and encompasses other variants that may be considered by those skilled in the art within the scope of the claims and in particular any combination of different embodiments described above.

Claims (18)

claims   1. Evaporator (10), in particular for a motor vehicle air-conditioning circuit, comprising: an evaporator core (12) comprising at least a first and a second ply (14, 16; 42, 44, 46; 42, 44, 46, 48, 50) extending in parallel planes, each sheet being formed of a series of parallel pipes traversed by a refrigerant fluid to be evaporated, so as to cool a flow of air passing through the planes of the plies (14, 16; 42, 44, 46; 42, 44, 46, 48, 50), and fluid distribution means (20, 22) disposed at both ends of the plies and connected to a fluid inlet (24). ) and a fluid outlet (26), said distributor means (20, 22) being configured to ensure the distribution and collection of the fluid in the different lines of each of the plies (14, 16, 42, 44, 46). 42, 44, 46, 48, 50) defining between the distribution means (20, 22) a circulation of the fluid in a given direction for each pipe, characterized in that it comprises at least one additional layer (18) disposed adjacent to the evaporator core (12) and cooperating with the distributor means (20, 22) so as to receive the fluid having circulated in the evaporator core (12) and delivering it to the fluid outlet (26).   2. Evaporator according to claim 1, characterized in that the additional ply (18) is disposed adjacent to the evaporator core on the side of the incident air flow (28).   3. Evaporator according to claim 1 or 2, characterized in that at least a portion of the refrigerant circulates in the additional ply (18) in a counterflow flow compared to a pass in the evaporator core (12). ).   4. Evaporator according to one of claims 1 to 3, characterized in that the distribution means (20, 22) are configured to define at least two different fluid passes in opposite directions in each of the first and second plies (14). 42, 44, 46, 42, 44, 46, 48, 50) of the evaporator core (12)   5. Evaporator according to one of the preceding claims, characterized in that the distribution means (20, 22) are configured to define a pass in one direction in the additional ply (18).   6. Evaporator according to one of the preceding claims, characterized in that the first web (14) comprises a number of successive fluid passes (30, 32, 34) which is greater than the number of passes (36, 38) of the second ply (16), so as to have, for each of the passes of the successive different plies, total flow sections of the fluid which are decreasing from the first ply (14) to the second ply (16), and the second ply (16); web (16) to the additional web (18).   7. Evaporator according to one of the preceding claims, characterized in that the first web (14) is located on the side of the fluid inlet (24).   8. Evaporator according to one of the preceding claims, characterized in that the relative dimensions of the pipes of the additional ply (18) and evaporator core pipes (12) are chosen so that the total overall section ( D2) pipes of the additional ply (18) is less than the total overall section (D1) of the plies of the plies of the evaporator core (12).   Evaporator according to claim 8, characterized in that the relative dimensions of the pipes of the additional ply (18) and those of the evaporator core (12) are chosen so that the total overall section ( D2) pipes of the additional ply (18) is less than one-third of the total overall section (D1) of the ply ducts of the evaporator core (12).   10. Evaporator according to one of the preceding claims1, characterized in that the distribution means (20, 22) are configured to allow the entry of the refrigerant into the web (46) of the evaporator core (12). adjacent to the additional ply (18) and the transfer to the additional ply (18), after passing through the evaporator core (12), of the fluid coming from the ply (42; 48) situated opposite the additional ply (18). 25   11. Evaporator according to one of claims 1 to 9, characterized in that the distribution means (20, 22) are configured to allow the refrigerant to enter the web (42; 48) located at the opposite the additional ply (18) (18), and the transfer to the additional ply (18), after passing through the evaporator core (12), of the fluid coming from the ply (46) situated adjacent to the additional ply (18).   12. Evaporator according to claim 10 or 11, characterized in that the evaporator core (12) comprises three plies (42, 44, 46) or five plies (42, 44, 46, 48, 50) or seven plies, so as to define in the whole of the evaporator respectively at least four passes or six steps or eight different fluid passes in opposite directions.   13. Evaporator according to one of the preceding claims, comprising a series of individual heat exchange plates defining parallel circulation blades successively traversed by the refrigerant and corresponding to a respective pipe of each of successive layers of the evaporator core. and the additional web (18).   14. Evaporator according to claim 13, characterized in that the distribution means (20, 22) are formed by a configuration of the fluid circuit defined by each individual plate of the stack.   15. An evaporator according to one of claims 1 to 12, comprising a series of individual tubes through which the refrigerating fluid flows and corresponding to a respective pipe of each of the successive layers (14, 16, 42, 44, 46; 44, 46, 48, 50) of the evaporator core (12) and the additional ply (18).   16. Evaporator according to claim 15, characterized in that the distribution means (20, 22) are formed by at least one manifold unit joining the plates or tubes at at least one of their ends. 5   17. Evaporator according to one of claims 13 to 16, characterized in that the plates or tubes are stacked (e) alternately with intermediate fins traversed by the air flow.   18. Evaporator according to one of the preceding claims, characterized in that the refrigerant is an azeotropic fluid or a zeotropic fluid.