FR3067797A1 - EVAPORATOR HAVING TWO TABS, ESPECIALLY FOR A MOTOR VEHICLE AIR CONDITIONING CIRCUIT, COMPRISING "U" TUBES AND CORRESPONDING AIR CONDITIONING CIRCUIT - Google Patents

Abstract

The invention relates to an evaporator (1), especially for a motor vehicle air conditioning circuit, comprising a stack of flat tubes for circulating a refrigerant fluid, the flat tubes forming two sheets (11, 12) extending in parallel planes each comprising at least three coolant circulation passes, the flat tubes delimiting between them air passages so as to cool a flow of incident air (9A) flowing through said passages through the successive layers of the evaporator (1). According to the invention, the first web (11) comprises an inlet passage (101) and an outlet passage (106) of the refrigerant fluid of the evaporator (1), said inlet and outlet passes (101, 106) being adjacent, the flat tubes forming the side passages of the evaporator defining a flow path of the refrigerant U, in a direction parallel to said incident air flow (9A) to be cooled.

Description

Two-layer evaporator, in particular for a motor vehicle air conditioning circuit, comprising U-shaped tubes and corresponding air conditioning circuit

1. Field of the invention

The invention relates to an evaporator, in particular for an air conditioning installation of a motor vehicle.

More specifically, it relates to evaporators having two superposed layers each comprising a plurality of pipes for circulation of a refrigerant fluid.

2. Prior art

The evaporators comprise, on the one hand, a core generally consisting of two layers formed by a plurality of parallel conduits or channels for the circulation of a refrigerant fluid and, on the other hand, means for distributing the refrigerant fluid arranged at the two ends of the layers to ensure the distribution and collection of the refrigerant in the various conduits of each of the layers.

The conduits are made either from pairs of adjoining plates having a plurality of walls which define channels / passages for the circulation of the coolant, or from tubes joined at their two ends by manifolds allowing the passage of the coolant from one tube to another.

In the case of plate evaporators, the internal structure of the pipes defines different zones which each form a circulation pass for the refrigerant.

In the case of tube evaporators, these are internal partitions provided in the manifolds which define these passes.

The distribution means (configuration of the plates or internal partitioning of the manifolds) are therefore designed to allow a circulation of the coolant in several passes, with reversal of the direction of circulation of the coolant from one pass to the next.

Conventionally, each of the two layers of these evaporators has three or four passes.

An air flow passes through the intervals between the fluid lines, and transfers heat to the refrigerant which passes from the liquid state to the gaseous state.

The air flow thus cooled can in particular be then used for air conditioning the passenger compartment of a vehicle.

Two-layer evaporators with several different fluid paths, so as to define, in parts of each layer, and / or from one layer to another, a flow of the fluid according to U-shaped circuits and / or with flows crossed (that is to say in opposite directions), are well known to those skilled in the art and widely described in the prior art.

The operation of these evaporators is satisfactory but it is necessary to further improve the heat exchange between the refrigerant and the air to be cooled.

This improvement notably involves maximizing the surface area useful for the heat exchange between the incident air and the refrigerant.

In this context, each layer of the evaporator comprises in its lower part and in its upper part means for distributing the refrigerant fluid in the layers, also called distributing means.

It has been observed that the zones of the evaporator situated at the level of these means for distributing the coolant are not useful for heat exchange since it is not possible to position therein intermediate fins intended for known, to be traversed by an air flow and to promote the heat exchange between the refrigerant and the air to be cooled.

This therefore limits the useful heat exchange area between the refrigerant and the air to be cooled.

It is also necessary to maintain good temperature uniformity between the different regions (right / left, up / down) of the evaporator, which implies controlling the evaporation process, in particular from the point of view of the distribution of the pressure losses within the various regions of the evaporator.

One of the aims of the invention is thus to design an evaporator with two layers, the structure of which promotes the heat exchange between the refrigerant and the air to be cooled.

Another object of the invention is to provide an evaporator with two layers, the structure of which defines a path for the refrigerant fluid which optimizes the various circulation passes of the refrigerant fluid with respect to each other and improves the evaporation process.

3. Summary of the invention

The invention provides for this purpose an evaporator, in particular for a motor vehicle air conditioning circuit, comprising a stack of flat tubes for circulation of a refrigerant forming two layers extending in parallel planes and each comprising at least three passes of circulation of the refrigerant, the flat tubes delimiting between them air passages so as to cool an incident air flow circulating by said passages through the successive layers of the evaporator.

According to the invention, the first layer comprises a first pass, called the inlet pass of the refrigerant fluid into the evaporator, and a last pass, called the outlet pass of the coolant fluid from the evaporator, the inlet and outlet being adjacent and the first sheet being situated on the side of the incident air flow to be cooled. The heat transfer fluid outlet pass is located on an edge of the first ply.

Still according to the invention, the flat tubes forming the side passes of said first layer and of the second layer of said evaporator, these side passes being located on the edges of the latter, define a path for the circulation of the refrigerant in U in a direction. parallel to said air flow to be cooled, and orthogonal to the stacking direction of the tubes.

The implementation of such flat U-shaped tubes allows the refrigerant to be turned over in the lower part or the upper part of the evaporator, depending on the orientation of these tubes.

The U-shaped path extends in a plane parallel to the air flow to be cooled.

This makes it possible to arrange intermediate fins for the heat exchange between the air and the evaporator up to the bottom or at the top of the latter.

It is thus possible to reduce the surface portion, also called zone, which is not useful for the heat exchange between the refrigerant and the air to be cooled, and therefore to improve this heat exchange.

The implementation of such flat U-shaped tubes also makes it possible to reduce the pressure drop at the level of the incident air flow, since a part of the fin replaces a part which did not previously allow the flow of air .

The implementation of flat U-shaped tubes at each of the lateral passes also makes it possible to maintain central symmetry in the arrangement of the evaporator.

The air flows at the right and left evaporator outlets can thus be constantly balanced.

An evaporator according to the invention also has the advantage that the hottest passes are arranged on the side of the incident air flow and the coldest passes are arranged on the side of the outlet of the air flow from the evaporator . The passes which are last traversed by the refrigerant, that is to say the coldest passes, are therefore arranged on the second ply.

This particular implementation of the inlet and outlet passes of the evaporator makes it possible to optimize the uniformity of the temperature of the air cooled at the outlet of the evaporator.

Such a configuration also makes it possible to improve the heat exchanges between the evaporator and the air passing through it since the temperature differential between the air flow passing through the evaporator and the temperature of the refrigerant is maximized.

Furthermore, the fact of placing the fluid outlet pass on one end of the first ply makes it possible to implement a conventional phase of overheating of the refrigerant fluid so that the fluid evaporates entirely before injection into the compressor d 'an air conditioning system, for example.

According to a particular aspect of the invention, the tubes of said stack are alternately stacked with fins, also called spacers, through which said incident air flow to be cooled.

According to a particular aspect of the invention, each sheet consists of a plurality of parallel pipes traversed by the refrigerant, at least one side pass comprising more pipes than at least one central pass.

Unlike a side pass, a "central pass" is not positioned at the edge of a sheet. The relative increase in the number of pipes of a side pass, in comparison with a central pass, makes it possible to increase the useful heat exchange surface of the side pass, while limiting the portions of surface dedicated to the circulation of the refrigerant. between the different passes.

According to a particular aspect of the invention, the fins arranged between the tubes of the side passes are longer than the fins arranged between the tubes of at least one central pass located between the side passes.

The relative increase in the length of the fins of a lateral pass, in comparison with a central pass, also makes it possible to increase the useful heat exchange surface of the lateral pass, while limiting the portions of surface dedicated to circulation. refrigerant between the different passes.

According to a particular aspect of the invention, the evaporator comprises six passes for circulation of the refrigerant, said first and second layers each comprise three passes for circulation of the refrigerant.

According to a particular aspect of the invention, said first layer successively comprises said last outlet pass, said first pass and a second pass for circulation of the refrigerant.

According to a particular aspect of the invention, said second sheet successively comprises a fifth pass, a fourth pass and a third pass for circulation of the refrigerant, arranged respectively opposite the last exit pass, the first pass and the second pass of the first layer.

According to a particular aspect of the invention, the U-shaped tubes of the lateral passes of a first edge of the evaporator are positioned in the opposite direction to the U-shaped tubes of the lateral passes of a second edge of the evaporator.

According to a particular aspect of the invention, each sheet consists of a plurality of parallel pipes traversed by the refrigerant and defined by the tubes, said last and the fifth pass comprising between 20% and 40% of said pipes.

According to another aspect of the invention, said last and fifth passes comprise approximately 40% of said pipes.

The first, second, third and fourth passes therefore comprise approximately 60% of the lines of the evaporator, or approximately 30% each.

Such a distribution of the pipes in the evaporator passes makes it possible to favor optimum performance of the evaporator in terms of temperature difference between the incident air and the air leaving the evaporator.

According to yet another aspect of the invention, said last and fifth passes comprise approximately 30% of said pipes.

The first, second, third and fourth passes therefore comprise approximately 70% of the evaporator lines, or approximately 35% each.

Such a distribution of the pipes in the evaporator passes makes it possible to favor optimal homogeneity of the temperature of the air leaving the evaporator.

According to one aspect of the invention, the evaporator comprises eight passes, said first and second layers each comprising four passes for circulation of the coolant.

According to one aspect of the invention, each pass of the evaporator comprises between thirty and fifty pipes in which the refrigerant circulates.

The invention also relates to an automobile air conditioning circuit comprising at least one evaporator as described above.

4. List of figures

Other characteristics and advantages of such evaporators according to the invention will appear more clearly on reading the following detailed description of two particular embodiments of the invention, given by way of simple illustrative and nonlimiting examples, and of the attached drawings. , among which :

Figure 1 is a schematic representation, seen from above, of the configuration of the refrigerant fluid circulation passes in an evaporator according to a first embodiment of the invention;

Figure 2 is a perspective view of the evaporator of Figure 1 showing the direction of fluid flow in the passes;

Figure 3 is a schematic side view of a U-shaped plate implemented in an evaporator according to the invention;

Figure 4 is a schematic front view of a two-layer evaporator and two passes of the prior art comprising a stack of U-shaped plates;

FIG. 5 is a schematic representation, front view, of the so-called useful and non-useful front surfaces of the evaporator according to the first embodiment of the invention;

Figure 6 is a schematic representation, seen from above, of the configuration of the coolant circulation passes in an evaporator according to a second embodiment of the invention;

Figure 7 is a perspective view of the evaporator of Figure 3 showing the direction of flow of the fluid in the passes; and FIG. 8 represents the pressure and temperature variation curves of the refrigerant circulating in an evaporator.

5. Detailed description of the invention

In the various figures, unless otherwise indicated, identical elements have the same reference numbers and have the same technical characteristics and operating modes.

The various embodiments according to the present invention are designed very particularly to optimize the pressure drops undergone by the refrigerant during the various circulation passes in the evaporator, thus leading to better control of the evaporation process and a better uniformity of the temperature of the air cooled at the outlet of the evaporator, in particular.

These various embodiments of the present invention also aim to maximize the useful front surface of the evaporator for the heat exchange between the incident air and the refrigerant.

The embodiments described below relate to an evaporator of the plate type which is used in a refrigerant circuit for air conditioning the passenger compartment of a motor vehicle.

5.1 Description of a first embodiment

Figures 1 and 2 illustrate an evaporator 1, according to a first embodiment, comprising an evaporator core 10 consisting of two adjacent layers 11, 12 extending in parallel planes.

The first layer 11 of the evaporator 1 is located on the side of the inlet of the incident air flow, or hot air, 9A to be cooled while the second layer 12 is located behind the first layer 11, that is to say say on the outlet side of the air flow, called cooled air flow 9B, of the evaporator 1.

Each sheet 11, 12 is formed of a plurality of parallel pipes 13 traversed by a refrigerant fluid so as to cool the air flow 9A successively passing through the first 11 and second 12 sheets.

An inlet port 131 and an outlet port 132 of refrigerant fluid are arranged on a side face of the evaporator 1.

The evaporator 1 is produced from a stack of flat tubes, each flat tube being formed of two sheets of metal sheet which are in contact with each other on their peripheral edges so as to define with their internal walls pipes 13 of refrigerant circulation.

The pipes 13 are thus produced from the individual plates connected to each other so as to define a predetermined circulation of the refrigerating fluid.

Between each flat tube is left a space for the passage of an air flow to be cooled.

In known manner, the plates are configured so as to define fluid distributing means at at least one of the two ends (upper and / or lower) of the sheets.

These distributing means distribute and collect the coolant in the various pipes 13 of the sheets 11, 12, by defining between the distributing means a circulation of the fluid in a given direction for each pipe 13.

In the embodiment of FIG. 2, the plates of the evaporator 1 have orifices at the upper end, the orifices being bordered by flanges so as to form an inlet collecting space connected to the inlet port 131 and an outlet manifold space connected to the outlet port 132 when the plates are stacked.

As shown in FIG. 1, the evaporator core 10 is divided into six zones, or passes, which are here distributed uniformly between the two layers 11, 12.

By "circulation pass" means the path of the refrigerant in one or more pipes 13 of a sheet.

In other words, the first ply 11 and the second ply 12 each comprise three passes.

Thus, the first layer 11 is divided into three zones along the length of the evaporator 1, defining from one edge to another three passes for the circulation of the refrigerant.

According to the invention, the first pass, called the coolant inlet pass, and the sixth pass, called the coolant exit pass or last pass, 106 of the evaporator 1, are arranged in the first layer 11 of the '' evaporator 1.

More specifically, the invention proposes to arrange these inlet passes 101 and outlet passes 106 adjacent to one another and to place the outlet pass 106 of the fluid on an edge of the first ply 11 (on the left in FIG. 1), and therefore near a side face of the evaporator.

A second pass 102 is arranged adjacent to the inlet pass 101 of the fluid, on the other edge of the first ply 11 (on the right in FIG. 1).

The inlet pass 101 is therefore placed in the middle of the first ply 11, between the outlet pass 106 and a second pass 102.

The second layer 12 is also divided into three zones along the length of the evaporator 1, defining three passes for circulation of the refrigerant fluid. This second layer successively has (from right to left in FIG. 1) a third pass 103, a fourth pass 104 and a fifth pass 105. The third pass 103 is located on an edge of the second layer 12 (on the right in the figure 1) and is opposite the second pass 102 of the first ply 11. The fifth pass 105 is located on the other edge of the second ply 12 (on the left in FIG. 1) and is opposite -vis the outlet pass 106 of the fluid from the first ply 11. The fourth pass 104, which is located opposite the inlet pass 101 of the fluid, is arranged in the middle of the second ply 12, between the fifth pass 105 and the third pass 103.

The evaporator 1 therefore comprises six successive passes 101, 102, 103, 104, 105, 106 which define a circuit for circulation of the refrigerant fluid between the inlet 131 and the outlet 132 of the fluid from the evaporator 1, with a reversal of the direction of circulation of the fluid to each successive pass, as illustrated in Figure 2.

More specifically, the direction of circulation of the adjacent passes (passes 103 and 105, for example) to a given pass (pass 104) is reversed with respect to the direction of circulation of the fluid in this pass (pass 104).

For example, for the first pass 101, the circulation of the fluid is done downward while for all the adjacent passes (the passes 106, 102 and 104) to this first pass 101, the circulation of the fluid is done upward.

This characteristic is applicable for all passes of evaporator 1.

This particular configuration of the evaporator 1 passes proves to be optimal both to maximize the temperature difference between the incident air flow 9A and the cooled air flow 9B after passing through the evaporator 1, as well as to preserve good temperature uniformity between the different regions (right / left, top / bottom) of evaporator 1.

In fact, as illustrated in FIG. 8, the inventors have observed that the temperature of the refrigerant fluid decreases as it circulates in the evaporator, due to the decrease in pressure (linked to pressure drops) of fluid between the inlet and the outlet of the fluid in the evaporator.

The coldest fluid circulation passes are therefore those which are located last in the circulation circuit.

Furthermore, it is known to overheat the coolant outlet pass (as illustrated on the right of the second curve in FIG. 8) so that the fluid, at the outlet of the evaporator, is present only in the gaseous phase and therefore at higher temperature, before injection into the compressor of the air conditioning circuit, for example.

On the basis of these observations, the inventors have chosen to arrange the fluid outlet pass 106, which must be overheated, on the first layer 11 of the evaporator 1, this first layer 11 being in contact with the incident air flow 9A (hot air).

The first 101 and second 102 passes, which are also the hottest since they are located at the start of the fluid circulation circuit, are also arranged on the first ply 11.

The fifth pass 105, which is the coldest pass since it is located at the end of the fluid circulation circuit, is arranged against the hottest pass, in this case the last exit pass 106, on the second layer 12 of the '' evaporator 1.

The third pass 103 and fourth pass 104 of the second ply 12, which are also considered to be cold passes for the same reasons as the fifth pass 105, are also arranged on the second ply 12, respectively against (or opposite) screws) the second pass 102 and first pass 101 of the first ply 11.

The invention therefore provides a configuration in which the hottest passes (namely passes 101, 102 and 106) are arranged on the first ply 11 and the coldest passes (namely passes 103, 104 and 105) on the second layer 12 of the evaporator 1, so as to maximize the temperature difference between the incident air flow 9A and the cooled air flow 9B after passing through the evaporator 1.

Furthermore, this configuration of the passes in the evaporator 1 makes it possible to balance the temperature of the passes arranged opposite (the pass 106 with the pass 105, the pass 101 with the pass 104, the pass 102 with the pass 103) in order to maintain good temperature uniformity between the different regions of evaporator 1.

The inversion of the direction of circulation of the fluid between two adjacent passes (of the same layer and of two distinct layers) also makes it possible to homogenize the temperature within the evaporator 1.

Still according to the invention, the passes 102 and 103 and the passes 105 and 106, positioned on the edges of the evaporator 1, are formed from a plurality of flat tubes of a first type, called U-shaped tubes.

The plates forming a U-shaped tube define a U-shaped circulation path of the refrigerant within the tube.

FIG. 3 is a front view of such a plate 2.

Such a U-shaped plate 2 consists of two longitudinal channels 2a and 2b comprising at their upper end an orifice 21 for admission and an orifice 23 for outlet of the coolant respectively and, at their lower end, a turning passage 22 allowing the refrigerant to circulate between the channels 2a and 2b of the plate 2 in a U where it circulates in opposite directions.

Of course, the orientation of the U-shaped plate 2 in FIG. 3 is chosen purely by way of illustration, such a U-shaped plate 2 being able to be positioned in one direction as in another, or in other words, with its passage turning 22 oriented downwards or upwards.

A U-shaped tube is here formed by two U-shaped plates 2 arranged one against the other, the channels 2a, 2b of the two facing plates forming conduits 13 each belonging to a pass.

FIG. 5 is a schematic front view, on the side of the second ply 12, of the evaporator 1 according to the first embodiment of the invention.

As described above, the evaporator 1 comprises on each of its edges a pair of passes 102 and 103, and 105 and 106, made up of a plurality of parallel U-shaped tubes connecting the two layers 11 and 12 together.

The U-shaped tubes of these passes 102, 103, 105, 106 are obtained by assembling U-shaped plates identical to that illustrated in FIG. 3.

At a first edge, the U-shaped tubes constituting the passes 102 and 103 are arranged so that their inlet and outlet orifices 21, 23 of the refrigerant are positioned in the lower part of the passes, and their turning passage 22 is positioned in the upper part.

According to this configuration and as illustrated by the directional arrows in FIG. 5, the refrigerant is returned to the upper part of the passes 102 and 103, which is included in the useful zone 3a of heat exchange between the refrigerant and the air passing through the evaporator 1.

At the opposite edge of the evaporator 1, the U-shaped tubes constituting the passes 105 and 106 are arranged in opposite direction relative to the passes 102 and 103 on the other edge.

Thus, the U-shaped tubes of the passes 105 and 106 are arranged in such a way that their inlet and outlet orifices 21, 23 of the coolant are positioned in the upper part of the passes, and that their turning passage 22 is positioned in lower part.

According to this configuration and as illustrated by the directional arrows in FIG. 5, the refrigerant is returned to the lower part of the passes 105 and 106, which is included in the useful zone 3a of heat exchange between the refrigerant and the air passing through the evaporator 1.

Unlike the useful heat exchange zones 3a, the surface portions of the evaporator 1 located at the level of the means for distributing and collecting the refrigerant in the passes do not allow satisfactory heat exchange, and therefore form zones that are not useful heat exchange 3b.

Such a configuration of the evaporator 1 makes it possible to permanently balance the air flows at the right and left outlets of the air conditioning circuit, due to the central symmetry observed in the arrangement of the evaporator 1.

In the central passes 101, 104, the tubes are not U-shaped, unlike the lateral passes, and have at their upper and lower ends inlet and outlet orifices for the refrigerant.

As illustrated in FIG. 5, the non-useful heat exchange zones 3b extend for these central passes 101, 104 at the upper and lower ends of the bundle.

FIG. 4 is a schematic view of an evaporator with two layers and two passes (ie one pass per layer, the passes being in the opposite direction) of the prior art, consisting of a stack of U-shaped plates identical to that illustrated on Figure 3.

In the illustrated implementation, the U-shaped tubes formed from these plates allow the refrigerant to be turned over in the lower part of the passes.

A portion of “non-useful” surface 3b is located at the upper end of the passes, at the level of the means of distribution and collection of the coolant. This surface portion 3b of the front surface of the evaporator is used for the circulation of the coolant and is therefore not useful for the heat exchange between the air and the coolant, which reduces the level of thermal power of the evaporator.

For example, the front surface dedicated to the circulation of refrigerant is 15%.

Fins, or spacers, extending to the bottom of the passes can be arranged between the U-shaped tubes to promote heat exchange between the air and the refrigerant. These fins cannot, however, extend in the upper part of the passes.

The surface portion covered by these fins is therefore qualified as "useful surface portion" 3a for the heat exchange between the air passing through the fins and the refrigerant.

Compared to this evaporator of the prior art, the extent of the useful surface portion of the evaporator 1 of the first embodiment is increased by 5%.

In other words, the heat exchange surface between the air and the refrigerant circulating in the evaporator is increased, and the front surface dedicated to the circulation of the refrigerant between the different passes is reduced.

In the case of a beam of equal height 200mm, this useful surface portion is increased by 6%.

The evaporator 1 has a central symmetry so that the air flows passing through the right and left parts of the evaporator are balanced

In addition, the pressure drop in the air flow is reduced since a part of the fin replaces a part which did not allow the air to flow.

More generally, the front heat exchange surface between the air and the refrigerant circulating in the evaporator 1 is increased, in comparison with the evaporators with two known layers, which makes it possible to improve the heat exchange.

In FIGS. 1 and 2, the first 11 ply and second ply 12 have identical dimensions.

The six zones, defining the six passes of the evaporator 1, are dimensioned such that the sixth pass 106 and fifth pass 105 together comprise between 20% and 40% of the total pipes of the evaporator 1.

More precisely, in FIG. 1, the zones defining the different passes of the evaporator 1 have dimensions such that the sixth pass 106 and fifth pass 105 together comprise approximately 40% of the total pipes of the evaporator 1, that is to say that is, about 20% each.

About 60% of the remaining lines are included in the first 101, second 102, third 103 and fourth 104 passes, or approximately 15% of the total lines of the evaporator 1 per pass.

This distribution of the lines 13 of the evaporator 1 in the various passes of the latter makes it possible to obtain an optimal thermal performance of the evaporator 1

In other words, with this distribution, the optimization of the difference between the temperature of the incident air 9A and the temperature of the cooled air 9B leaving the evaporator 1 is favored.

In a variant (not illustrated), the zones defining the different passes of the evaporator have dimensions such that the sixth and fifth passes 106, 105 together comprise approximately 30% of the total pipes of the evaporator 1, that is to say - say about 15% each.

The first 101, second 102, third 103 and fourth 104 passes therefore comprise approximately 70% of the remaining lines, or approximately 17.5% each of the total lines of the evaporator 1.

This distribution of the lines 13 of the evaporator 1 in the various passes of the latter makes it possible to obtain an optimal compromise between the thermal performance and the uniformity of the temperature of the cooled air 9B at the outlet of the evaporator.

It is noted that, in this first embodiment, each pass of the evaporator 1 comprises between thirty and fifty lines 13.

According to a particular aspect of the invention, at least one lateral pass comprises more parallel pipes than at least one central pass.

The relative increase in the number of pipes of a side pass, in comparison with a central pass, makes it possible to increase the useful heat exchange surface of the side pass, while limiting the portions of surface dedicated to the circulation of the refrigerant between the different passes.

According to another particular aspect of the invention, which can be implemented alternately or in combination, the fins of at least one lateral pass are longer than the fins of at least one central pass.

The relative increase in the length of the fins of a lateral pass, in comparison with a central pass, also makes it possible to increase the useful heat exchange surface of the lateral pass, while limiting the portions of surface dedicated to the circulation of the refrigerant between the different passes.

According to a particular aspect of the invention, not shown, the areas not useful for the heat exchange 3b are covered with an anticorrosion coating.

5.2 Description of a second embodiment

Figures 6 and 7 illustrate an evaporator 100, according to a second embodiment of the invention.

Similarly to the embodiment described above, the evaporator 100 comprises an evaporator core 10 consisting of two adjacent layers 11, 12 extending in parallel planes.

The first layer 11 of the evaporator 1 is located on the side of the inlet of the incident air flow 9A to be cooled, while the second layer 12 is located behind the first layer 11, that is to say on the side from the outlet of the cooled air flow 9B from the evaporator 1.

Each sheet 11, 12 is formed of a plurality of parallel pipes 13 traversed by a refrigerant fluid so as to cool the incident air flow 9A passing successively through the first 11 and second 12 sheets.

As shown in FIG. 6, the evaporator core 10 is divided into eight zones, or passes, which are here uniformly distributed between the two layers 11, 12. In other words, the first layer 11 and the second layer 12 each include four passes.

The configuration of the eight passes of the evaporator 100 is substantially similar to that of the evaporator 1 described above.

Indeed, the evaporator 100 comprises eight successive passes 111, 112, 113, 114, 115, 116, 117, 118 which define a circuit for circulation of the refrigerant fluid between the inlet 131 and the outlet 132 of the fluid from the evaporator 100, with an inversion of the direction of circulation of the fluid on each successive pass, as illustrated in FIG. 4.

According to the invention, the inlet 131 and the outlet 132 of refrigerant fluid are arranged in the first layer 11 of the evaporator 100.

The first ply 11 therefore comprises the first pass 111, called the fluid inlet pass, and the eighth pass 118, called the last pass or fluid outlet pass, of the evaporator 1.

More specifically, the invention proposes to arrange these passes 111, 118 adjacent to one another and to place the last pass 118 on an edge of the first ply 11 (on the left in FIG. 3).

This particular configuration of the evaporator passes proves to be optimal both to maximize the temperature difference between the incident air flow 9A and the cooled air flow 9B after passing through the evaporator 100, as well as to maintain a good temperature uniformity between the different regions (right / left, top / bottom) of the evaporator 100.

Indeed, the last pass 118, which must be overheated, is disposed on the first ply 11 of the evaporator 100, this ply 11 being oriented towards the side of the incident air flow 9A (hot air).

The first 111, second 112 and third 113 passes, which are also the hottest since located at the start of the fluid circulation circuit, are also arranged on the first ply 11.

The seventh pass 117, which is the coldest pass since it is located at the end of the fluid circulation circuit, is arranged against the hottest pass, that is to say the eighth and last pass 118, on the second layer. 12 of evaporator 100.

The fourth 114, fifth 115, and sixth 116 passes, which are also considered cold passes for the same reasons as the seventh pass 117, are also arranged on the second ply 12, respectively against the third 113, second 112 and first 111 passes.

The invention therefore provides a configuration in which the hottest passes (passes 111, 112, 113 and 118 in this case) are arranged on the first ply 11 and the coldest passes (passes 114, 115, 116 and 117 in this case) on the second layer 12 of the evaporator 100, so as to maximize the temperature difference between the incident air flow 9A and the cooled air flow 9B after passing through the evaporator 100.

Furthermore, this configuration of the passes in the evaporator 100 allows a balancing of the temperature of the passes arranged opposite (the pass 117 with the pass 118, the pass 116 with the pass 111, the pass 115 with the pass 112, and the pass 114 with the pass 113) in order to maintain good temperature uniformity between the different regions of the evaporator 100.

In this second embodiment, the direction of circulation of the passes adjacent to a given pass is also reversed with respect to the direction of circulation of the fluid in this pass.

For example, for the first pass 111, the circulation of the fluid is done downward while for all the adjacent passes (the passes 118, 112 and 116) to this first pass 111, the circulation of the fluid is done upward.

This characteristic is applicable to all the other passes of the evaporator 100.

The inversion of the direction of circulation of the fluid between two adjacent passes also makes it possible to homogenize the temperature within the evaporator 100.

Still according to the invention, the passes 113 and 114, as well as the passes 117 and 118, positioned on the edges of the evaporator 1, consist of a plurality of parallel U-shaped tubes connecting the two plies 11 and 12 together .

These edge or side passes have the same technical advantages as those highlighted in the context of an evaporator 10 according to the first embodiment, as described above.

The U-shaped tubes of these passes 113, 114, 117, 118 are obtained by assembling U-shaped plates identical to that illustrated in FIG. 3.

At a first edge, the U-shaped tubes constituting the passes 117 and 118 are arranged so that their inlet and outlet orifices 21, 23 of the refrigerant are positioned in the upper part of the passes, and their turning passage 22 is positioned in the lower part.

At a second edge, the U-shaped tubes constituting the passes 113 and 114 are arranged so that their inlet and outlet orifices 21, 23 of the refrigerant are positioned in the upper part of the passes, and their turning passage 22 is positioned in the lower part.

5.3 Other aspects and variants

The two embodiments described above relate to two-layer evaporators with respectively three and four circulation passes per layer.

It is obviously understood that the invention also applies to evaporators having five, six or a greater number of passes per layer, without departing from the principle of the invention.

The evaporator according to the invention can be implemented in HVAC ("Heating, Ventilation and / or Air conditioning") or HVAC ("Heating,

Ventilation and Air-Conditioning (in English) of motor vehicles.

By way of nonlimiting example, the fixing of the evaporator in the receptacle can be carried out by means of a slide-type connection, in which the upper and lower portions of the evaporator slide in corresponding grooves made in the receptacle .

Claims (9)

1. Evaporator (1), in particular for an air conditioning circuit of a motor vehicle, comprising a stack of flat tubes for circulation of a refrigerant, said flat tubes forming two layers (11, 12) extending in parallel planes and each comprising at least three coolant circulation passes, the flat tubes delimiting between them air passages so as to cool an incident air flow (9A) flowing through said passages through successive layers (11, 12) of the evaporator (1,100), said first ply (11) comprising a first pass (101, 111), said pass for entering the refrigerant fluid in the evaporator (1), and a last pass (106, 118), said evaporator coolant outlet pass (1), said inlet (101, 111) and outlet (106, 118) passes being adjacent, said first ply (11) being located on the flow side incident air (9A) to be cooled, and said outlet pass (1 06, 118) of the heat transfer fluid being located on an edge of said first ply (11), characterized in that the flat tubes forming the lateral passes of said first ply (11) and of the second ply (12) of said evaporator (1 , 100), located on the edges of the latter, define a path for the circulation of the U-shaped coolant, in a direction parallel to said incident air flow (9A) to be cooled. 2. Evaporator (1) according to claim 1, characterized in that the flat tubes of said stack are alternately stacked with fins, or spacers, traversed by said incident air flow (9A) to be cooled. 3. Evaporator (1) according to claim 1 or 2, characterized in that the fins or spacers arranged between the flat tubes of the side passes (102, 103, 105, 106) are longer than the fins arranged between the flat tubes d '' at least one central pass (101,104) located between the side passes. 4. Evaporator (1) according to one of claims 1 to 3, characterized in that it comprises six passes of circulation of the refrigerant, said first and second layers (11, 12) each comprising three passes of circulation of the refrigerant . 5 5. Evaporator (1) according to claim 4, characterized in that the U-shaped tubes of the side passes of a first edge of the evaporator (1) are positioned in the opposite direction to the flat U-shaped tubes of the side passes of a second edge of the evaporator (1). 6. Evaporator (1) according to claim 4 or 5, characterized in that each layer (11, 12) consists of a plurality of parallel conduits (13) traversed by the refrigerant defined by the flat tubes, said last pass (106) and the fifth pass (105) positioned opposite the last pass (106) comprise between 20% and 40% of said conduits (13) of the evaporator (1). 15 7. Evaporator (100) according to one of claims 1 to 3, characterized in that it comprises eight passes, said first and second layers (11, 12) each comprising four passes of circulation of the refrigerant. 8. Evaporator (1, 100) according to claim 6 or 7, characterized in that each pass of the evaporator (1) comprises between thirty and fifty pipes 20 (13). 9. Automotive air conditioning circuit comprising at least one evaporator (1) according to one of claims 1 to 8.