FR3034510A1 - HEAT EXCHANGER FOR AN AIR CONDITIONING LOOP FOR A MOTOR VEHICLE - Google Patents

Abstract

Heat exchanger (20), arranged to effect a heat exchange between a first fluid flowing inside said heat exchanger and a second fluid flowing outside said heat exchanger, comprising a beam formed of at least a first ply (22a, 22b, 22c, 22d) and a second ply (22a, 22b, 22c, 22d) in which the first fluid circulates, the first ply (22a, 22b, 22c, 22d) being delimited by a first end face (22a ', 22a ", 22b', 22b", 22c ', 22c ", 22d', 22d") with respect to the direction of flow of the second fluid and a second end face (22a 22a, 22b ', 22b', 22b ", 22c ', 22c", 22d', 22d ") and the second web (22a, 22b, 22c, 22d) being delimited by a third end face (22a ', 22a', 22a ''), 22b ', 22b ", 22c', 22c", 22d ', 22d ") and a fourth end face (22a', 22a", 22b ', 22b ", 22c', 22c", 22d ', 22d "). According to the invention, said plies (22a, 22b, 22c, 22d) are communicated or isolated in a variable manner via at least one movable flap (30).

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to the field of heat exchangers and in particular those of an air conditioning loop, in particular a reversible air-conditioning loop. More particularly, the invention relates to a heat exchanger between an interior air flow intended to be distributed in a passenger compartment of a vehicle, and a heat transfer fluid. State of the Prior Art A motor vehicle is commonly equipped with a ventilation, heating and / or air conditioning system for regulating the aerothermal parameters of the air contained inside the passenger compartment of the vehicle. Generally, such an installation comprises in part a first circuit for thermally treating an air flow. A first heat transfer fluid, water and / or glycol in particular, circulates inside said circuit for conveying heat near a first heat exchanger, such as a radiator on the air. The latter is crossed by a flow of air to be heated before being delivered inside the cabin.

Such an installation also partly comprises a second circuit for cooling a second air flow before it is delivered inside the passenger compartment. Said circuit comprises a plurality of elements inside which circulates successively a subcritical refrigerant fluid of the type R134a, R1234yf or a transcritical fluid, carbon dioxide or R744 in particular. The elements of said circuit comprise at least one compressor, a second heat exchanger, an expansion device, an evaporator and an accumulator or a desiccant bottle. The second heat exchanger allows the cooling fluid to cool by yielding heat to a heat transfer fluid. This last 3034510 2 is likely to be indifferently a gas, especially air, or a liquid, water and / or glycol in particular. The evaporator is also traversed by a flow of air to be cooled before being delivered inside the passenger compartment.

In general, the overall efficiency of said installation relies significantly on the respective efficiencies of the heat exchangers that the installation comprises. Indeed, it is constantly sought by the designers of ventilation, heating and / or air conditioning means to optimize the heat exchange between the heat transfer fluid that flows 10 inside the radiator and the air flow, and secondly between the heat transfer fluid to be heated and another heat source, for example a refrigerant circulating in a heat pump loop, the two fluids exchanging heat by an additional exchanger, or for example by a thermal loop linked to the engine.

For this reason, it is known that in order to facilitate such heat exchanges, it is desirable that the flow rate of the heat transfer fluid inside the respective heat exchangers of said installation be sufficient to allow a good heat exchange and to ensure in the various parts the exchanger a good distribution. Thus, in operation, the heat exchanger is always traversed by a maximum water flow resulting in that, under certain operating conditions, the water leaving the heat exchanger is at a temperature lower than that desired during operation in heating mode and at a higher temperature when operating in cooling mode (when in heating mode and higher in cooling mode) For example, on a hybrid vehicle operating in thermal mode, the available heat provided by the engine cooling can be used to heat the living space by circulating in the radiator a large flow (> 1000 1 / h). Conversely, in electric mode when the heating of the heat transfer fluid is provided by a heat pump via a brine exchanger refrigerant, and especially if the refrigerant is the R744, the power required to 3034510 3 heating respecting a good efficiency of the heat pump must be ensured with a low flow rate in the same radiator (from 501 / h to 2001 / h). However, it turns out that an efficient high-throughput heat exchanger does not make it possible to ensure good distribution of the low-flow fluid. In contrast, a heat exchanger adapted to low flow will present an unacceptable loss of charge at high speed. SUMMARY OF THE INVENTION The present invention aims at optimizing the energy consumption of an air conditioning loop by proposing an exchanger capable of operating at different flow rates without causing a loss of pressure that is too high at the maximum flow rate. For this, the invention proposes a heat exchanger, arranged to perform a heat exchange between a first fluid flowing inside said heat exchanger and a second fluid flowing outside said heat exchanger, comprising a beam formed by at least a first ply and a second ply in which the first fluid flows, the first ply being delimited by a first end face with respect to the direction of flow of the second fluid and a second end face and the second ply being delimited by a third end face and a fourth end face. According to the invention, said plies are placed in communication or isolated in a variable manner via at least one movable flap.

In this way, the heat exchanger comprises moving elements allowing or obstructing the flow of the first fluid. The first fluid corresponds to the coolant or heat transfer fluid while the second fluid is air. These movable elements thus make it possible to modify the circulation of the fluid in the heat exchanger, by closing or opening connections between the different plies or branches of the heat exchanger. By circulating the fluid on channels in series or in parallel, it follows that the flow rate varies per channel. The invention therefore proposes to vary the flow of the fluid, and therefore its flow, to adapt to the energy requirements of the operating conditions of the air conditioning loop. It is thus possible to ensure the distribution of calories in the passenger compartment in different modes requiring a low flow (thermodynamic heating) or a high flow (heating by the heat engine).

Particular embodiments according to the invention propose that: at least three of the end faces are distinct and arranged in different planes; - The movable valve is made of a shape memory material; The movable valve is made of a material able to open and / or close by variations of the pressure differential of the first fluid or by the dynamic pressure of the first fluid on faces of the movable valve, said valve being suitable to return to a rest position; the heat exchanger comprises at least two movable flaps the opening or closing of which is effected sequentially; at least one of the movable valves is arranged on at least one deflecting and / or perpendicular wall; the heat exchanger comprises at least two passes, each pass being placed in communication via said movable valve, a passage corresponding to a direction of flow of the first fluid within the beam, the two passes being in two directions opposed on the same surface; - The heat exchanger comprises two manifolds with at least one movable valve being disposed within at least one manifold; At least one of the movable valves is disposed in pipe elements integral with the heat exchanger. The invention also relates to an air conditioning loop comprising a heat exchanger as described above.

BRIEF DESCRIPTION OF THE FIGURES Other features and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures, which illustrate: FIG. 1 illustrates a side view of a heat exchanger heat ; - Figure 2 illustrates a side view of a heat exchanger according to the invention; FIG. 3 illustrates a side view of a heat exchanger according to the invention; FIG. 4 illustrates a side view of a heat exchanger according to the invention; - Figures 5A and 5B schematically illustrate different modes of operation of the heat exchanger in a view from above.

DETAILED DESCRIPTION OF THE EMBODIMENTS In order to provide an optimized efficiency for a heating, ventilation and / or air-conditioning installation, it is essential that the respective heat exchanges effected between a first fluid and a second fluid themselves be the most satisfactory possible. . One way to do this is to vary the flow rates of the first fluid flowing inside the heat exchanger. For this, the invention proposes to use a heat exchanger 20 capable of optimizing heat transfer over a wide range of flow rates while maintaining a reasonable pumping power. Indeed, the heat exchanger 20 according to the invention is able to modify the circulation of a working fluid FT circulating within the exchanger as a function of the flow rate. The invention is not limited to the type of heat exchanger, so that the heat exchanger 20 may correspond to a radiator or an evaporator to achieve heat exchange between on the one hand a flow of air 3 , or second fluid, flowing outside the tubes of the heat exchanger and secondly a working fluid FT, or first fluid circulating inside the tubes of the heat exchanger, the fluid of work FT 3034510 6 corresponding to a refrigerant FR, such as R744 or R134a, or a heat transfer fluid FC such as brine. The heat exchanger 20, illustrated in FIG. 1, corresponds to a stack of 5 tubes, or plates, defining channels within which a working fluid FT circulates. The heat exchanger 20 comprises a first and second collector chambers 21, 23 each formed at a respective lateral end of the heat exchanger 20 with the tubes being disposed between the collector chambers 21, 23 parallel to each other. The collecting chamber 21 corresponds to the first chamber through which the working fluid FT passes. Thus, inside the heat exchanger 20, the working fluid FT flows successively inside the first collecting chamber 21, then through the series of tubes and then through the second collecting chamber 23 to be finally evacuated out of the heat exchanger 20.

The tubes may be stacked to define a beam, here with four plies 22a, 22b, 22c and 22d each having a respective thickness Pi, P2, P3 and P4. A web can be defined as a series of tubes arranged in the same plane characterized by a height H and a length L data. A heat exchanger 20 comprises four plies 22a, 22b, 22c, 22d which implies that the working fluid FT can flow in four distinct planes. The thicknesses of the plies 22a, 22b, 22c, 22d may be of equal dimensions, as illustrated in FIG. 1, or according to one embodiment not shown, the plies 22a, 22b, 22c, 22d may be of different thickness, Especially with the thickness P1 being the largest and the thickness P4 the smallest. As illustrated in FIG. 2, according to a particular embodiment, the first ply 22a is delimited by a first end face 22a 'and a second end face 22a ". The second ply 22b is delimited by a third end face 22b' and a fourth front face 22b ". The third ply 22c is delimited by a fifth front face 22c 'and a sixth end face 22c' '. Finally, the last ply 22d is delimited by a seventh front face 22d' and an eighth end face 22d ''. At least five of the end faces are distinct and arranged in different planes. Said end faces 22a-22d "are defined as the faces of the heat exchanger 20 being traversed by the air flow 3. The heat exchanger 20 according to the invention and as illustrated in FIGS. 5, comprises movable valves 30, which will be described later, allowing the flow of the working fluid FT between the plies 22a, 22b, 22c, 22d.The heat exchanger 20 comprises at least two passes, that is to say say at least two sets of tubes defined in the same plane, or in the same sheet, with the working fluid FT flowing successively in a first direction inside a first set of tubes, then in a reverse direction in the first direction inside a second set of tubes As illustrated in FIG. 2, inside the heat exchanger 20, the working fluid FT circulates successively inside the first collector chamber 21 and then through the first set of tubes in a The working fluid FT then passes through a second collecting chamber 23 and then through the second set of tubes in the opposite direction to the first set of tubes. The working fluid FT flows back into the first collection chamber 21 and then through a third set of tubes to be finally discharged out of the heat exchanger 20. Baffle plates, or partitions, 26 are arranged in the collecting chamber 21 to force the flow of the working fluid FT into a given set of 25 tubes. The number of deflector plates 26 arranged depends on the number of passes desired. Here, to make 3 passes, two deflector plates 26 have been arranged in the heat exchanger 20, more precisely one in each collecting chamber 21, 23. The movable valves 30, described later, are arranged on the deflector plates 26 and allow to put the passes in communication. However, the invention is not limited neither to the number of deflector plates 26 nor to the number of movable valves 30 arranged on said deflector plates 26.

As we have seen previously, the heat exchanger 20 comprises at least two sheets, that is to say at least two sets of tubes defined in two separate planes. The working fluid FT can flow in one direction inside the two sets of tubes simultaneously or successively. As illustrated in FIG. 2, according to a particular embodiment, inside the heat exchanger 20, the working fluid FT flows successively inside the first collecting chamber 21 and then through the first set of tubes in one direction. The working fluid FT then passes through a second collecting chamber 23 and then through the second set of tubes 10 in the opposite direction to the first set of tubes. The working fluid FT flows back into the first collection chamber 21 and then through a third set of tubes to be finally discharged out of the heat exchanger 20.

As shown in FIG. 3, according to a particular embodiment, inside the heat exchanger 20, the working fluid FT passes through the first collecting chamber 21 and then flows simultaneously through the two sets of tubes. webs 22a and 22b in the same direction. The working fluid FT then passes through the second collecting chamber 23 and then through a third and fourth set of tubes, the plies 22c, 22d, in the opposite direction to the two plies 22a and 22b. In Figure 3, a single baffle plate, or partition, perpendicular 28 has been arranged in the first collector chamber 21 to force the simultaneous circulation of the working fluid FT in the two plies 22a and 22b. By perpendicular deflector plate 28, it will be understood that a perpendicular deflector plate 28 is perpendicular to a deflector plate 26 described above. In other words, if the deflector plate 26 extends in the horizontal or longitudinal direction of the heat exchanger 20, in this case the perpendicular deflector plate 28 extends in the vertical or transverse direction of the heat exchanger 20. The number of perpendicular deflector plates 28 arranged depends on the path that a user wishes to give to the flow of the working fluid FT. The movable valves 30, described later, are arranged on the perpendicular partitions 28 and make it possible to put in communication the plies 22a, 22b, 22c, 22d. However, the invention does not limit either the number of perpendicular deflector plates 28 or the number of movable valves 30 arranged on said perpendicular partitions. Of course, it is possible to design a heat exchanger 20 comprising several baffle plates 26 and / or perpendicular deflector plates 28 so as to give the user as much freedom as possible as to the choice of the flow, and therefore of the distance and the flow rate of the working fluid FT passing through the heat exchanger 20. According to a non-illustrated embodiment, a heat exchanger with four layers, each comprising three passes, should have four deflector plates 26, two in each collector chamber 21,23 and three perpendicular deflector plates 28 in the collector chambers 21,23. As we have seen, it is necessary for the FT working fluid 15 to pass from one web and / or to another. For this purpose, movable valves 30 have been arranged in each deflector plate 26 and each perpendicular deflector plate 28 as illustrated in FIG. 4 which represents an embodiment combining the particular embodiments of FIGS. 3 and 4. Each movable valve 30 is adapted to be deformed under the influence of the working fluid FT so as to let it circulate in a sheet and / or passes depending on certain parameters, such as for example the temperature or the dynamic pressure of the working fluid FT. A movable valve 30 is defined as any organ capable of opening or closing the communication between two distribution volumes. The communication between two volumes can be obtained by one or more movable valves arranged in parallel. Different types of movable valve 30 may be used to allow the flow of the working fluid FT into a web and / or pass. The movable valves 30 may for example be moved by a motorized actuator adapted to choose the degree of opening of a valve according to the flow requirements of the working fluid FT.

Another possibility consists in using movable valves 30 made of shape memory material and in particular an alloy such as nickel-titanium or titanium-aluminum with a two-way memory effect capable of having two stable positions, one of which above a so-called critical temperature and the other below. These shape memory materials are sensitive to temperature, so that it becomes possible to allow the tilting of a valve through a temperature variation causing the deformation and movement of the movable valve 30.

A final possibility is to use movable valves 30 made of material capable of opening or closing by variations of the pressure differential or by the dynamic pressure of the working fluid FT, such as, for example, elastic blades, consisting of example of a bimaterial complex associating a metal and a rubber or elastic polymer, or a hinged blade combined with a device acting as a return spring, the two aforementioned blades being able to deform or move according to the pressure differential applied, and returning to their original position in the absence of constraints. The tilting of the movable valve 30 is made in this case by means of a pressure variation combined with a spring effect generating the movement of the movable valve 30. The last two types of valve are particularly advantageous since they are suitable for manage the flow of the working fluid FT independently without external energy input. As seen above, the movable valves 30 are arranged on the deflector plates 26 and / or perpendicular deflector plates 28. However, the invention is not limited to the number of perpendicular deflector plates 26 and / or deflector plate 28, nor to the number of movable valves 30 arranged on said deflector plates and / or perpendicular.

The heat exchanger 20 is therefore able to operate in different modes, for example, an optimized mode for a low flow rate of the working fluid FT, and the other mode optimized for a high flow rate. Low flow operation involves reducing the flow section and increasing the distance traversed by the working fluid FT. This homogenizes the mapping of the temperatures of the air flow 3 at the exchanger outlet and improves the efficiency of the heat exchanger 20 due to a better distribution and greater homogeneity of the flow of the working fluid FT. Such an operation is illustrated in FIG. 5A, where a heat exchanger 20, in a view from above, has four plies 22. The heat exchanger 20 can have several passes (not shown) to increase heat exchange between the flow of air 3 and the working fluid FT. The working fluid FT in such a mode of operation through successively 4 layers.

High flow operation is to increase the flow section to reduce the pressure drop. Such a mode of operation is illustrated in FIG. 5B, where a heat exchanger 20, according to a view from above, has four sheets 22, we can see in this mode that the working fluid FT flows over a distance reduced by half compared to low flow operation. In effect, the working fluid FT passes through the first collecting chamber 21 and then flows simultaneously through two plies 22. The working fluid FT then passes into the second collecting chamber 23 and then circulates again simultaneously in two other plies 22. The heat exchanger 20 may have several passes (not shown) to increase heat exchange between the air stream 3 and the working fluid FT. The working fluid FT in such a mode of operation successively passes through two plies. The movable valves 30 may be made of shape memory material which deforms as a function of temperature. In this case, for a cold start, the working fluid FT will be at a low temperature, and the movable valves 30 will adopt a configuration for a low flow rate which will be maintained as long as the temperature or flow rate remains below a certain threshold by for example, 60 ° C or 100 liters / hour. However, if the temperature or the flow rate exceeds this threshold the movable flaps 30 switch to have a high flow mode of operation.

Of course, the movable valves 30 may be made of different materials in order to have different deformation profiles and thus better adapt to the need for flow.

It will also be noted that the opening or closing of each flap will not necessarily take place for the same temperature or the same flow rate of transition. To provide a stable and gradual transition between the low rate and high rate modes, it may be necessary to sequentially open or close the different valves in a specific order. For example, for a transition between the low rate mode (Fig.

5A) and broadband (Fig.

5B), it will first be possible to open the one or more movable valves 30 of the chamber 23, then the closure of the one or more movable valves 30 located in the center of the chamber 21, and finally the opening of the lateral valves 30 of In other words, the heat exchanger 20 comprises a plurality of movable valves 30, the opening or closing of which is effected sequentially and non-simultaneously to switch from one mode of operation to another. The principle is the same with the movable valves 30 being made of material 15 able to deform under the influence of the dynamic pressure of the fluid combined with a spring effect. Similarly, the valves can be made of different materials or with different opening tare in order to have different deformation profiles and better adapt to the need for flow.

As can be seen in FIGS. 5A and 5B, it is possible to remove the valves 30a and 30b, the latter always remaining open regardless of the operating mode of the vehicle, and thus avoiding putting the associated perpendicular deflector plate 28.

According to a non-illustrated embodiment, it is possible to arrange at least one of the movable valves in duct elements integral with the exchanger to have an additional control element on the flow rate. Since the movable valves 30 must be disposed in the heat exchanger 20 during its assembly, the movable valves 30 should be made of materials compatible with the brazing conditions. Alternatively, it is also possible to provide openings and joints at the collector chambers 21, 23 to allow their introduction after soldering.

The invention also relates to an air conditioning loop comprising a heat exchanger as described above. It should be understood, however, that these exemplary embodiments are given by way of illustration of the object of the invention. The invention is not limited to these embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms and other variants that may be considered by those skilled in the art within the scope of the present invention and in particular any combination of the various embodiments described above. 10

Claims (10)

REVENDICATIONS1. Heat exchanger (20), arranged to carry out a heat exchange between a first fluid (FT) flowing inside said heat exchanger and a second fluid (3) circulating outside said heat exchanger, comprising a beam formed of at least one first ply (22a, 22b, 22c, 22d) and a second ply (22a, 22b, 22c, 22d) in which the first fluid (FT) flows, the first ply (22a, 22b, 22c, 22d) being delimited by a first end face (22a ', 22a ", 22b', 22b", 22c ', 22c ", 22d', 22d") with respect to the flow direction of the second fluid (3) and a second end face (22a ', 22a ", 22b', 22b", 22c ', 22c ", 22d', 22d") and the second web (22a, 22b, 22c, 22d) being delimited by a third end face (22a ', 22a ", 22b', 22b", 22c ', 22c ", 22d', 22d") and a fourth end face (22a ', 22a ", 22b', 22b", 22c ' , 22c ", 22d ', 22d"), characterized in that said plies (22a, 22b, 22c, 22d) are communicated or isolated in a manner variable via at least one movable valve (30). 2. Heat exchanger according to claim 1, characterized in that at least three of the end faces (22a ', 22a ", 22b', 22b", 22c ', 22c ", 22d', 22d") are distinct and arranged according to different plans. 3. Heat exchanger according to one of claims 1 or 2, characterized in that the movable valve (30) is made of a shape memory material. 25 4. Heat exchanger according to one of claims 1 or 2, characterized in that the movable valve (30) is made of a material adapted to open and / or close by variations in the pressure differential of the first fluid or by the dynamic pressure of the first fluid on faces of the movable valve 30 (30), said valve (30) being adapted to return to a rest position. 5. Heat exchanger according to one of the preceding claims, characterized in that it comprises at least two movable flaps (30) whose opening or closing takes place sequentially. 3034510 15 6. Heat exchanger according to one of the preceding claims, characterized in that at least one of the movable valves (30) is arranged on at least one baffle wall (26) and / or a perpendicular baffle wall (28). 5 7. Heat exchanger according to one of the preceding claims, characterized in that it comprises at least two passes, each pass being placed in communication via said movable valve (30), a pass corresponding to a direction of circulation. the first fluid in the beam, the two passes being in two opposite directions on the same surface. 8. Heat exchanger according to one of the preceding claims, characterized in that it comprises two manifolds (21,23) with at least one movable valve (30) being disposed within at least one box collector (21,23). 9. Heat exchanger according to one of claims 1 to 7, characterized in that at least one of the movable valves (30) is disposed in pipe elements integral with the heat exchanger. An air conditioning loop comprising a heat exchanger (20) according to any one of the preceding claims.