Patent Description:
Traditionally, vehicles comprise at least one thermal treatment system adapted to thermally treat the propulsion system of the vehicle and/or the passenger compartment of such vehicle. Such thermal treatment systems usually comprises at least one refrigerant fluid circuit which comprises at least one heat exchanger adapted to operate a heat exchange between the refrigerant fluid and an air flow. The refrigerant fluid circuit can also comprise another heat exchanger adapted to operate a heat exchange between the air flow and the refrigerant fluid, or between the refrigerant fluid and another refrigerant fluid. The air flow and/or the other refrigerant fluid can then be used to thermally treat the propulsion system and/or the passenger compartment. Document [<CIT>] shows an exemplary system described above. <CIT> discloses a heat exchanger comprising an intermediate tank.

Those thermal treatment systems are often arranged in a front part of the vehicle wherein the available space is limited. As a result, there is a need to reduce as much as possible the bulk of such thermal treatment system.

The present invention aims to resolve at least this issue by providing a heat exchange unit comprising at least two heat exchangers which are part of the same refrigerant fluid circuit and arranged in order to be the less cumbersome as possible.

An object of the present invention thus concerns a heat exchange unit for a vehicle, comprising at least a first heat exchanger adapted to perform a heat exchange between a refrigerant fluid and an air flow, at least a second heat exchanger adapted to operate a heat exchange between the refrigerant fluid and the air flow, the first heat exchanger being arranged downstream of the second heat exchanger along the air flow direction, the heat exchange unit comprising at least one accumulation device hydraulically connected to both the first heat exchanger and the second heat exchanger, at least a first connector and a second connector, the first connector being hydraulically connected to the accumulation device and to the second connector and the second connector being hydraulically connected to the first connector and to the second heat exchanger, at least the second connector being screwed to the first connector. For instance, the first connector can be brazed on the first heat exchanger and the second connector can be brazed to the second heat exchanger. In other words, the first connector is formed as a single-piece with, at least, the first heat exchanger while the second connector is formed as a single-piece with the second heat exchanger. The second connector being screwed to the first connector, this second connector and the second heat exchanger can easily be replaced without damaging the rest of the exchange unit.

According to the invention, the first connector comprises at least a first channel and a second channel, the first channel being hydraulically connected to the first heat exchanger and to the accumulation device and the second channel being hydraulically connected to the accumulation device and to the second connector. That is to say that the first channel of the first connector connects an outlet of the first heat exchanger to an inlet of the accumulation device while the second channel of this first connector connects an outlet of the accumulation device to an inlet of the second connector.

According to the invention, the second connector comprises at least one conduit hydraulically connected on one hand to the second channel of the first connector and on the other hand to the second heat exchanger. To put it another way, the conduit connects the second channel of the first connector to an inlet of the second heat exchanger. According to an embodiment of the invention, this conduit is a unique conduit.

According to the invention, at least one of the connectors is geometrically interposed between the accumulation device and, at least, the second heat exchanger. Advantageously, both the first and the second connectors are geometrically interposed between the accumulation device and, at least, the second heat exchanger. By the words "geometrically interposed" we here mean that the concerned connector(s) is(are) physically arranged between the accumulation device and the second heat exchanger. Advantageously, such an arrangement reduces the global bulk of the heat exchange unit.

According to the invention, the second connector may comprise a connecting plug adapted to be received in an orifice arranged in the first connector. Especially, the connecting plug is adapted to be received in an orifice which comes out on the second channel of the first connector. If so, the connecting plug is connected to the second channel arranged in the first connector, that is to say that the connecting plug connects the second channel of the first connector to the conduit of the second connector.

Advantageously, the first heat exchanger is arranged upstream of the second heat exchanger along a direction of circulation of the refrigerant fluid. To put it another way, the refrigerant fluid that reaches the second heat exchanger has already been subjected to a heat exchange with the air flow within the first heat exchanger. Arranging the first heat exchanger upstream the second heat exchanger along the direction of circulation of the refrigerant fluid but downstream said second heat exchanger along the air flow direction advantageously results in a maximisation of the temperature difference between the refrigerant fluid and the air flow with which the heat exchange is performed, and, thus in an optimization of such heat exchange. According to an embodiment of the invention, the refrigerant fluid thus reaches the first heat exchanger in a gaseous state, exits it in a liquid state and is then subcooled in the second heat exchanger. Advantageously, the efficiency if the refrigerant fluid circuit which comprises the heat exchange unit of the invention is therefore globally improved.

According to an aspect of the invention, the first heat exchanger mainly extends in a first plan, the second heat exchanger mainly extends in a second plan, the first plan and the second plan being parallel to each other.

According to the invention, the first heat exchanger and the second heat exchanger each comprises at least one heat exchange area, at least one entry manifold adapted to distribute the refrigerant fluid in the heat exchange area and at least one exit manifold adapted to collect the refrigerant fluid that leaves said heat exchange area, the entry manifolds and the exit manifolds of the heat exchangers each extending along a main axis perpendicular to a direction of circulation of the refrigerant fluid in the heat exchange areas. According to an embodiment of the invention, the first heat exchanger's exit manifold and the second heat exchanger's entry manifold can be arranged on a same side of the heat exchange unit. According to this embodiment, the first heat exchanger's entry manifold and the second heat exchanger's exit manifold are advantageously arranged on an opposite side of the heat exchange unit.

For example, the accumulation device can be arranged on the same side of the heat exchange unit than the first heat exchanger's exit manifold and the second heat exchanger's entry manifold. The accumulation device advantageously extends along a main direction parallel to the main axis of extension of the first heat exchanger's exit manifold. The main direction of extension of the accumulation device can also be parallel to a main axis of extension of the second heat exchanger's entry manifolds and perpendicular to the direction of circulation of the refrigerant fluid in the heat exchange areas.

Optionally, the accumulation device can extend all along a dimension of the first heat exchanger measured between two ends of this first heat exchanger, along the main axis of extension of the first heat exchanger's entry manifold.

According to an embodiment of the invention, the second heat exchanger presents a smaller height than the first heat exchanger, such heights being measured along a direction included in a main plan of extension of the first heat exchanger and perpendicular to the main direction of circulation of the refrigerant fluid in the first heat exchanger's heat exchange area. Advantageously, such an arrangement virtually divides the first heat exchanger, and especially the heat exchanger area of this first heat exchanger, in an upper part adapted to be crossed by a first air flow and a lower part adapted to be crossed by a second air flow which also crosses the second heat exchanger. As mentioned earlier, the second air flow crosses the second heat exchanger before crossing the lower part of the first heat exchanger.

The present invention also relates to a thermal treatment system for a vehicle, comprising at least one refrigerant fluid circuit carrying at least the heat exchange unit such as the one mentioned above, and at least one circulation device adapted to circulate the refrigerant fluid.

According to an aspect of the invention, the refrigerant fluid is adapted to carry and exchange heat by changing its state. According to this aspect of the invention, the circulation device is a compression device and the refrigerant fluid circuit also comprises at least one expansion device, that is to say a device adapted to reduce the pressure of the refrigerant fluid which goes through it.

Other features and advantages of the invention are to be described in the detailed description of the invention given hereunder in relation with different views of the invention illustrated on the following figures:.

In the following specification, the orientations given are related to the orientation of a heat exchange unit <NUM> according to the invention. On the figures, an L, V, T coordinate system is illustrated in which a longitudinal direction is parallel to a longitudinal axis L, a vertical direction is parallel to a vertical axis V and a transversal direction is parallel to a transversal axis T. According to the examples given, the longitudinal axis L is perpendicular to both the vertical axis V ant to the transversal axis T, the vertical axis V is perpendicular to both the longitudinal axis L and to the transversal axis T and the transversal axis T is perpendicular to both the longitudinal axis L and to the vertical axis V. For instance, once the heat exchange unit <NUM> of the invention is implemented in a vehicle, the vertical axis V corresponds to a direction perpendicular to the road on which such vehicle is adapted to run.

<FIG> illustrates, schematically, a thermal treatment system <NUM> according to the invention. As shown, such thermal treatment system <NUM> comprises at least one refrigerant fluid circuit <NUM> which carries at least one heat exchange unit <NUM> according to the invention, at least one circulation device <NUM> adapted to circulates the refrigerant fluid and at least one evaporator <NUM>. According to the illustrated example, a refrigerant fluid RF is adapted to carry and to exchange heat by changing its state. For instance, the refrigerant fluid RF can be chosen among 1234YF, R134a or CO2.

As a result, the circulation device <NUM> adapted to circulate the refrigerant fluid is a compression device and the refrigerant fluid circuit <NUM> also comprises at least one expansion device <NUM>. The compression device <NUM> is adapted to compress the refrigerant fluid RF before it reaches the heat exchange unit <NUM>. Within the heat exchanger unit <NUM>, the refrigerant fluid RF is adapted to exchange heat with an air flow AF which, as schematically illustrated, crosses the heat exchange unit <NUM>. According to the illustrated embodiment, the heat exchange unit <NUM> works as a condenser with respect to the refrigerant fluid, that is to say that the refrigerant fluid is cooled and liquified by passing through such heat exchange unit. In other words, the refrigerant fluid is adapted to give calories to the air flow AF which crosses said heat exchange unit <NUM>. The cooled refrigerant fluid can then be used to thermally treat another part of the vehicle, such as the passenger compartment or the propulsion system of the vehicle.

The refrigerant fluid RF thus exits the heat exchange unit <NUM> in a liquid state and goes through the expansion device <NUM> in which its pressure is reduced. The cooled liquid refrigerant fluid RF then reaches the evaporator <NUM> in which its temperature is raised until the refrigerant fluid evaporates. The refrigerant fluid RF exits the evaporator <NUM> in a gaseous state and then reaches again the compression device <NUM> to start a new thermodynamic cycle. The evaporator <NUM> can be adapted to perform a heat exchange between the refrigerant fluid and an air flow or between the refrigerant fluid and another fluid without departing from the scope of the invention.

It is understood that this is only an example of carrying the invention which does not restrict it. For instance, the heat exchange unit according to the invention can be used as an evaporator.

The heat exchange unit <NUM> according to the invention can for instance be arranged in a front part of a vehicle and the air flow AF which crosses it can be generated by the movement of the vehicle which carries such heat exchange unit <NUM>. Alternately, or additionally, the thermal treatment system <NUM> of the invention can comprise at least one ventilation device adapted to generate the air flow, for instance when the vehicle is stopped or in dense traffic.

<FIG> is a perspective view of the heat exchange unit <NUM> adapted to be crossed by the air flow AF. As shown, the heat exchange unit <NUM> comprises at least a first heat exchanger <NUM>, at least a second heat exchanger <NUM> and at least one accumulation device <NUM>. Especially, the air flow AF is adapted to cross both the first heat exchanger <NUM> and the second heat exchanger <NUM>.

The first heat exchanger <NUM> and the second heat exchanger <NUM> have similar shapes. First of all, the first heat exchanger <NUM> mainly extends in a first plan P1 and the second heat exchanger <NUM> mainly extends in a second plan P2 parallel to the first plan P1. According to the orientation given on the figures, the first plan P1 and the second plan P2 are both vertical and longitudinal plans, that is to say plans in which the vertical axis V and the longitudinal axis L extend.

Each of these heat exchangers <NUM>, <NUM> comprises at least one heat exchange area <NUM>, <NUM> wherein the heat exchange between the refrigerant fluid and the air flow AF is performed, and at least one manifold <NUM>, <NUM> adapted to distribute and/or to collect the refrigerant fluid in and from the respective heat exchange areas <NUM>, <NUM>. According to the illustrated embodiment, each heat exchanger <NUM>, <NUM> comprises two manifolds <NUM>, <NUM>, among which one entry manifold 212a, 222a adapted to distribute the refrigerant fluid in the heat exchange areas <NUM>, <NUM> and one exit manifold 212b, 222b adapted to collect the refrigerant fluid from those heat exchange areas <NUM>, <NUM> once the heat exchange has been performed. According to this embodiment, each of the manifolds <NUM>, <NUM> extends along a main axis A, A' parallel to the vertical axis V and the manifolds <NUM>, <NUM> of one of the heat exchangers <NUM>, <NUM> are arranged at two sides of the concerned heat exchanger <NUM>, <NUM> opposed to one another along the longitudinal axis L. Especially, the first heat exchanger's exit manifold 212b and the second heat exchanger's entry manifold 222a extend parallel to a main axis A while the first heat exchanger's entry manifold 212a and the second heat exchanger's exit manifold 222b extend parallel to another main axis A'. According to the illustrated embodiment, the main axis A and the other main axis A' are parallel to each other. In other words, the manifolds <NUM>, <NUM> extend perpendicularly to a main direction of circulation of the refrigerant fluid along the heat exchange areas <NUM>, <NUM>. Advantageously, the air flow AF also circulates perpendicularly to a main plan of circulation of the refrigerant fluid along the heat exchange areas <NUM>, <NUM>.

The first heat exchanger <NUM> presents a greater height than the second heat exchanger <NUM>. The "height" of a heat exchanger <NUM>, <NUM> is a dimension measured along the vertical axis V, between two ends of the concerned heat exchanger, opposed along such vertical axis V. As a consequence, the air flow AF can be virtually separated in a first air flow AF1 which crosses only an upper part <NUM> of the first heat exchanger <NUM> and in a second air flow AF2 which crosses a lower part <NUM> of the first heat exchanger <NUM> and the entire heat exchange are <NUM> of the second heat exchanger <NUM>. The first air flow AF1 thus exchanges heat only with the refrigerant fluid circulating in the upper part <NUM> of the first heat exchanger <NUM> while the second air flow AF2 exchanges heat with the refrigerant fluid that circulates in the lower part <NUM> of the first heat exchanger <NUM> and with the refrigerant fluid which circulates in the second heat exchanger <NUM>.

According to the illustrated embodiment, the second heat exchanger <NUM> is arranged upstream of the first heat exchanger <NUM> along the air flow AF, AF1, AF2 direction, and especially along the second air flow AF2 direction. As a result, the second air flow AF2 presents a cooler temperature when it enters the second heat exchanger <NUM> than when it enters the lower part <NUM> of the first heat exchanger <NUM>.

Advantageously, the first heat exchanger <NUM> is arranged upstream of the second heat exchanger <NUM> along a direction of circulation of the refrigerant fluid in the heat exchange areas <NUM>, <NUM>. In other words, the refrigerant fluid enters the heat exchange unit <NUM> through the first heat exchanger's entry manifold 212a, circulates along the first heat exchanger's heat exchange area <NUM> until it reaches the first heat exchanger's exit manifold 212b. As detailed below the first heat exchanger's exit manifold 212b is hydraulically connected to the second heat exchanger's entry manifold 222a thanks to, at least, the accumulation device <NUM>. The refrigerant fluid exiting the first heat exchanger's exit manifold 212b thus reaches the second heat exchanger's entry manifold 222a, then circulates along the second heat exchanger's heat exchange area <NUM> and finally reaches the second heat exchanger's exit manifold 222b. It is thus understood that the first heat exchanger's entry manifold 212a and the second heat exchanger's exit manifold 222b are both hydraulically connected to the refrigerant fluid circuit of the thermal treatment system earlier described.

As a result, the refrigerant fluid which circulates in the first heat exchanger <NUM> is warmer than the refrigerant fluid which circulates in the second heat exchanger <NUM>. Advantageously, such an arrangement permits to maximise the temperature difference between the refrigerant fluid which circulates in the heat exchange areas <NUM>, <NUM> and the air flow which crosses such heat exchange areas <NUM>, <NUM>, and especially between the second air flow AF2 and the refrigerant fluid which circulates in the lower part <NUM> of the first heat exchanger <NUM>.

Especially, the refrigerant fluid enters the first heat exchanger's entry manifold 212a in a gaseous state and at high pressure. The refrigerant fluid then circulates along the first heat exchanger's heat exchange area <NUM> wherein it exchanges heat with the airflow AF. More particularly, the gaseous refrigerant fluid first circulates in the upper part <NUM> of the first heat exchanger <NUM> wherein it exchanges heat with the first airflow AF1, then it reaches the lower part <NUM> of the first heat exchanger <NUM> wherein it exchanges heat with the second airflow AF2. As a result of the heat exchange operated within the upper part <NUM> of the first heat exchanger <NUM>, the refrigerant fluid may reach the lower part <NUM> of the first heat exchanger <NUM> in a biphasic state. Advantageously, the refrigerant fluid finishes its condensation within the lower part <NUM> of the first heat exchanger <NUM>, that is to say by exchanging heat with the second airflow AF2 in order to be in a liquid state when it reaches the second heat exchanger <NUM>. In this second heat exchanger <NUM>, the refrigerant fluid keeps exchanging heat with the second air flow AF2. As mentioned earlier, the second heat exchanger <NUM> is arranged upstream the first heat exchanger <NUM> along the main direction of circulation of the air flow AF, and particularly along the direction of circulation of the second air flow AF2. As a consequence, the heat exchange between the refrigerant fluid which circulates in the second heat exchanger <NUM> results in a subcooling of the refrigerant fluid. Especially, the second heat exchanger <NUM> of heat exchange unit <NUM> according to the invention is adapted to make the refrigerant fluid's temperature drop under its liquefaction temperature. Advantageously, such subcooling permits to improve the global efficiency of the refrigerant fluid circuit which comprises the heat exchange unit <NUM> of the invention. Between the first heat exchanger <NUM> and the second heat exchanger <NUM>, the refrigerant fluid is temporarily stocked in the accumulation device <NUM>. Advantageously, this accumulation device <NUM> is adapted to contain the circulating refrigerant fluid in order to compensate the refrigerant fluid leaks which are unavoidable during the vehicle's life cycle.

As illustrated, this accumulation device <NUM> extends along a main direction Y parallel to the vertical axis V, that is to say parallel to the main axis of extension A, A' of the manifolds of both the first heat exchanger <NUM> and the second heat exchanger <NUM>. This accumulation device <NUM> is hydraulically connected to the first heat exchanger <NUM>, and particularly to the exit manifold 212b of this first heat exchanger <NUM>, and to the second heat exchanger <NUM>, and particularly to the entry manifold 222a of this second heat exchanger <NUM>.

According to the invention, a first connector <NUM> hydraulically connects the first heat exchanger's exit manifold 212b to the accumulation device <NUM> and a second connector <NUM> hydraulically connects the first connector <NUM> to the second heat exchanger's entry manifold 222a.

According the illustrated embodiment of the invention, the first connector <NUM> can be brazed on the heat exchange unit <NUM>, and especially to, at least, the first heat exchanger's exit manifold 212b, while the second connector <NUM> is brazed only to the second heat exchanger's entry manifold 222a and screwed to the first connector <NUM>. Advantageously, when needed, the second connector <NUM> and the second heat exchanger <NUM> can be replaced without having to also replace the rest of the heat exchange unit <NUM>.

As schematically represented on <FIG>, the first connector <NUM> comprises at least a first channel <NUM> and at least a second channel <NUM>. Those channels <NUM>, <NUM> are schematically represented in dotted lines. As shown, the first channel <NUM> is hydraulically connected to the first heat exchanger's exit manifold 212b on one hand and to the accumulation device <NUM> on the other hand while the second channel <NUM> is hydraulically connected to the accumulation device <NUM> on one hand and to the second connector <NUM> on the other hand. In other words, the first channel <NUM> is connected to an inlet of the accumulation device <NUM> while the second channel <NUM> is connected to an outlet of this accumulation device <NUM>.

The second connector <NUM> comprises one conduit <NUM>, especially a single conduit <NUM>, also represented with dotted lines on <FIG>. As illustrated, this conduit <NUM> is hydraulically connected to the second channel <NUM> of the first connector <NUM> and to the second heat exchanger's entry manifold 222a.

As shown, the accumulation device <NUM> is arranged on a side of the heat exchangers <NUM>, <NUM> and extends parallel to the vertical axis V of the illustrated coordinate system. Particularly, the accumulation device <NUM> extends on the same side of the heat exchangers <NUM>, <NUM> than the first heat exchanger's exit manifold 212b and the second heat exchanger's entry manifold 222a. Advantageously, the second channel <NUM> of the first connector <NUM> is connected to a lower part <NUM> of the accumulation device <NUM>, that is to say to a part of this accumulation device <NUM> which faces the second heat exchanger <NUM>. Once mounted on the intended vehicle, the second heat exchanger <NUM> is closer to the road on which said vehicle runs than the first heat exchanger <NUM>. In other words, the invention uses the gravity to ensure that the second channel <NUM> of the first connector <NUM> is always arranged under the level of refrigerant fluid in a liquid state contained in the accumulation device <NUM>. Advantageously, this arrangement ensures the continuous supplying of the second heat exchanger <NUM> with refrigerant fluid in a liquid state.

The channels <NUM>, <NUM> and the conduit <NUM> are for instance also represented on <FIG> which is a cross-section view of the first connector <NUM> and the second connector <NUM>, this cross-section view being realized thanks to a vertical and transversal plan, that is to say a plan in which both the vertical axis V and the transversal axis T are included.

As illustrated on <FIG>, the second connector <NUM> is screwed to the first connector <NUM>. In order to screw these connectors <NUM>, <NUM>, at least one hole <NUM>, <NUM> is arranged in both the first connector <NUM> and the second connector <NUM>, each of those holes <NUM>, <NUM> being adapted to receive one screw <NUM>. In other words, the hole <NUM> arranged in the first connector <NUM> and the hole <NUM> arranged in the second connector <NUM> face each other and receive the same screw <NUM> once the connectors <NUM>, <NUM> are assembled. As shown, the hole <NUM> arranged in the first connector <NUM> is a blind hole while the hole <NUM> arranged in the second connector <NUM> traverses said second connector <NUM>.

As illustrated, the second connector <NUM> also comprises at least one connecting plug <NUM> which at least partially extends in an orifice <NUM> arranged in the first connector <NUM>. Especially, this connecting plug <NUM> extends parallel to the transversal axis T and comes out on the second channel <NUM> of the first connector <NUM> on one hand and on the conduit <NUM> of the second connector <NUM> on another hand. To put it another way, this connecting plug <NUM> hydraulically connects the first connector <NUM> to the second connector <NUM> by connecting the first connector's second channel <NUM> to the second connector's conduit <NUM>.

Now referring to <FIG>, we are going to describe the second connector <NUM> which is adapted to be screwed on the first connector <NUM>.

As illustrated, the second connector <NUM> has a general parallelepipedic shape, thus comprising at least one front face <NUM>, one rear face <NUM> linked together thanks to one first side face <NUM> and one second side face <NUM>. At least one cut <NUM> is formed in the front face <NUM> in such a way that second connector <NUM> presents an upper part 250a and a lower part 250b, the upper part 250a presenting a width w1 smaller than a width w2 of the lower part 250b. Those width w1, w2 are both measured along the transversal axis T, between the front face <NUM> and the rear face <NUM> of the second connector <NUM>.

As earlier described, a hole <NUM> adapted to receive the screw is arranged in the second connector <NUM>. Especially, this through-hole <NUM> is arranged in the upper part 250a of the second connector <NUM>, and the cut <NUM> is advantageously adapted to receive the screw head.

The rear face <NUM> of this second connector <NUM> carries the connecting plug <NUM> adapted to be received in the orifice formed in the first connector. According to the illustrated embodiment, the connecting plug <NUM> extends parallel to the transversal axis T but it is understood that it is only an example of how to execute the invention and that this connecting plug <NUM> could present another orientation without departing from the scope of the invention.

This connecting plug <NUM> is thus connected to the second channel of the first connector on one hand and to the conduit previously described on the other hand. Although it is not shown on <FIG>, this conduit comes out on the second side face <NUM> of the second connector <NUM>. As partially illustrated, this second side face <NUM> comprises at least one rail 255a adapted to encompass the second heat exchanger's entry manifold, said second side face <NUM> being in contact with said second heat exchanger's entry manifold.

The present invention therefore provides a new architecture of a heat exchange unit adapted to be received in a front part of a vehicle, such heat exchange unit being less bulky than the heat exchange units known from prior art.

Claim 1:
Heat exchange unit (<NUM>) for a vehicle, comprising at least a first heat exchanger (<NUM>) adapted to perform a heat exchange between a refrigerant fluid (RF) and an air flow (AF, AF1, AF2), at least a second heat exchanger (<NUM>) adapted to operate a heat exchange between the refrigerant fluid (RF) and the air flow (AF, AF1, AF2), the first heat exchanger (<NUM>) being arranged downstream of the second heat exchanger (<NUM>) along the air flow (AF, AF1, AF2) direction, the heat exchange unit (<NUM>) comprises at least one accumulation device (<NUM>) hydraulically connected to both the first heat exchanger (<NUM>) and the second heat exchanger (<NUM>), at least a first connector (<NUM>) and a second connector (<NUM>), characterised in that the first connector (<NUM>) is hydraulically connected to the accumulation device (<NUM>) and to the second connector (<NUM>) and the second connector (<NUM>) is hydraulically connected to the first connector (<NUM>) and to the second heat exchanger (<NUM>), at least the second connector (<NUM>) being screwed to the first connector (<NUM>), wherein at least one of the connectors (<NUM>, <NUM>) is geometrically interposed between the accumulation device (<NUM>) and, at least, the second heat exchanger (<NUM>).