Patent Application
20100186934
The invention relates to heat exchangers, in particular for motor vehicles.
It relates more specifically to a heat exchanger including two collection boxes opposite one another each delimiting a first chamber for a first fluid and a second chamber for a second fluid, as well as a core of tubes inserted between the two collection boxes and comprising first tubes communicating with the first chambers of the two collection boxes and second tubes communicating with the second chambers of the two collection boxes, in which each first tube is joined to a second tube so as to form a module enabling heat exchange between the first tube and the second tube, in which the modules are stacked and mutually spaced apart so as to enable a third fluid to pass, which washes over the core of tubes.
Such a heat exchanger can be part of a heating, ventilation and/or air conditioning device, in particular for a motor vehicle, as taught, for example, by the publication FR 2 861 166.
In this particular use in motor vehicles, the heat exchanger can be, for example, an air conditioning evaporator through which a refrigerant passes so as to cool the air flow and produce cooled air sent into the vehicle interior.
The heat exchanger can also be a heating radiator through which a warm fluid passes, normally installed in the cooling loop of the vehicle engine, so as to heat the air flow and produce warm air sent into the vehicle interior.
In the aforementioned type of heat exchanger, the first fluid, which is the refrigerant or heat transfer fluid, can exchange heat with a second fluid, which is an accumulation fluid, while the third fluid, which washes over the core, is formed by the air flow to be sent into the vehicle interior.
In the case of a classic air conditioning circuit, the fluid is a refrigerant, which, in the following order, passes through: a compressor, a condenser or a gas cooler according to the refrigerant used, an expansion valve and an evaporator, before returning to the compressor. In the evaporator, the refrigerant changes from a liquid phase or a liquid/vapor phase to a vapor phase by receiving heat from the air flow, which is thus cooled. Such a circuit is classically passed through by a refrigerant consisting of a fluorinated hydrocarbon such as that known by the designation R 134A.
Air conditioning circuits passed through by a refrigerant operating according to a supercritical cycle, such as, for example, carbon dioxide (CO2) are also known.
A disadvantage of the known evaporators is that their capacity to cool the air flow is dependent on the operation of the compressor and the circulation of the refrigerant in the air conditioning circuit. In other words, the air flow is no longer cooled once the compressor is stopped.
In most motor vehicles, the compressor is driven by means of the engine and is therefore stopped once the engine has stopped.
Currently, to meet in particular anti-pollution standards, motor vehicles are being produced so as to ensure that the internal combustion engine stops when the vehicle is in neutral gear or stopped, and as the internal combustion engine is stopped, the air conditioning is also stopped. The stopping of the internal combustion engine has the effect of stopping the compressor and therefore stopping the circulation of refrigerant in the air conditioning circuit. This results in discomfort for the passenger(s) of the vehicle due to an absence of an air conditioned air flow after several seconds of blowing.
A similar problem may occur if the heat exchanger is a heating radiator, due to the fact that the heat transfer fluid is caused to circulate by a pump, which is classically driven by the internal combustion engine of the vehicle. Thus, the stopping of the engine causes the pump to stop and therefore the circulation of fluid to stop. This results in discomfort, especially when the outside temperature is very low.
In a heat exchanger of the type mentioned in the introduction, the presence of a second fluid, which is an accumulation fluid, enables these disadvantages to be avoided.
Indeed, this second fluid enables accumulation either of cold (by consequently releasing heat), or of heat, when the engine of the vehicle is operating and of restoring this cold or this heat, in the vehicle interior, when the engine is stopped.
FR 2 863 044 describes a heat exchanger that operates on the same principle with an accumulation fluid, but in which a single collection box is provided and each of the modules includes two U-shaped tubes.
The heat exchangers according to the publications FR 2 861 166 and FR 2 863 044 are generally satisfactory, but the methods of assembly thereof present problems of inserting tubes in the collection box(es).
In addition, the production of collection boxes requires a large number of components in order to enable the first fluid and the second fluid to be distributed.
The invention is intended in particular to overcome the aforementioned disadvantages.
It thus proposes a heat exchanger of the type defined in the introduction, in which the first tube and the second tube forming a module are in contact over their entire length, the second tube has ends offset with respect to the ends of the first tube, so that the ends of the first tubes and the ends of the second tubes can be received alternately in insertion holes of the collection box, spaced apart by a constant pitch.
Thus, in a single module, the first and second tubes are joined so as to enable an exchange of heat between the first fluid and the second fluid that they contain, but the ends of the second tube are curved and offset, i.e. off-centered, with respect to the corresponding ends of the first tube, which off-centering corresponds to the pitch of the insertion holes of the collection boxes. The modules can thus be stacked and inserted between the two collection boxes, with the latter having insertion holes spaced two-by-two with a constant pitch.
In other words, a first tube of a module can be inserted into an insertion hole adjacent to another insertion hole, which receives the end of a second tube of an adjacent module.
According to another feature of the invention, the first tube has a rectilinear body from one to the other of its ends. Moreover, the second tube has a rectilinear body, in particular ending with two bent and offset ends. Advantageously, the ends of the second tube are bent in the form of a bayonet.
In another preferred embodiment of the invention, the collection box comprises a collection plate in which the insertion holes are provided for the first and second tubes, a second distribution plate arranged against the collection plate, forming a stop for the ends of the second tubes, delimiting the second chamber in fluid communication with the second tubes, and comprising openings for the ends of the first tubes, a first distribution plate arranged against the second distribution plate, forming a stop for the ends of the first tubes delimiting the first chamber in fluid communication with the first tubes, and a closing assembly arranged against the first distribution plate, opposite the second distribution plate.
Thus, the collection box is formed by at least four components, namely, in series: the collection plate, the second distribution plate, the first distribution plate and the closing assembly.
Although this closing assembly can be produced as a single piece, it is preferable for it to include an intermediate plate arranged against the first distribution plate and a lid covering the first distribution plate and jointly defining chambers for distributing the first fluid in the first distribution plate according to a defined path.
In the following description, provided solely as an example, reference is made to the appended drawings, in which:
a to 8d diagrammatically show four successive steps of assembly of the heat exchanger of
The following detailed description refers to a heat exchanger produced in the form of an air conditioning evaporator enabling an accumulation fluid to be stored, with the understanding that the invention is not limited to this particular use and also covers, in particular, heating radiators.
The heat exchanger 10 shown in
Between the two collection boxes 12 and 14, a core 16 is inserted, which forms the core of the heat exchanger 10 and which includes first tubes 18 and second tubes 20. Each first tube 18 is joined to a second tube 20 in order to jointly form a module 22.
Corrugated spacers 24 form disruptors and area arranged between two adjacent modules 22 so as to increase the surface for heat exchange with a fluid washing over the core 16, in particular an air flow.
The first tubes 18 are suitable for being passed through by a first fluid F1, which, in the example considered, consists of a refrigerant. The second tubes contain a second fluid F2, which, in the example considered, consists of an accumulation fluid and more specifically a cold accumulation fluid. Finally, the core is washed over by a third fluid F3, which is air and which passes between the modules 22 at the level of the corrugated spacers 24.
The second fluid F2 can be static in the second tubes 20 or circulate in the second tubes 20, which are then coupled to a circulation loop of the second fluid F2.
The first fluid F1 circulates in the heat exchanger 10 from an inlet manifold 26 to an outlet manifold 28, which, in the example, are connected to the collection box 12. According to the example embodiment of
As can be seen in
The first tube 18 and the second tube 20 are in contact over their entire lengths, along one of their respective large faces. Each first tube 18 in this case has a rectilinear body from one to the other of its ends 30.
However, the second tube 20 has ends 32, which are off-centered with respect to the ends 30 of the first tube 18. In particular, the ends 32 of the second tube 20 are curved and offset.
Thus produced, the ends 30 of the first tubes 18 and the ends 32 of the second tubes 20 can be received alternately in insertion holes 34 arranged respectively in the collection boxes 12 and 14. The insertion holes 34 of the collection box 12 are shown in
The insertion holes 34 are each surrounded by a collar 36. The collar 36 preferably comprises a lower chamfer in order to facilitate the simultaneous insertion of the ends 30 and 32 of the first and second tubes 18 and 20 into the respective insertion holes 34.
The insertion holes 34 and the collars 36 are formed in a collection plate 38 of the upper collection box 12. The lower collection box 14 has a similar collection plate 40, as shown in
Advantageously, the offset or off-centering of the ends 32 of the tubes 20 is produced by a double-bend in the form of a bayonet. Thus, each end 32 of the second tube 20 extends in a direction parallel to the axial direction of the body of the actual second tube 20.
The collection box 12 delimits a first chamber 42 for circulation of the first fluid F1, which communicates with the respective ends of the first tubes 18 and a second chamber 44 for circulation of the fluid F2, which communicates with the respective ends of the second tubes 20. The collection box 14 comprises similar chambers.
The term “chamber” as used here refers to an internal volume that can be made in a single piece or a plurality of pieces and that is suitable for containing a fluid communicating with the ends of the corresponding tubes.
In the example, the second fluid is an accumulation or storage fluid, which is immobile, and the heat exchanger thus performs a static storage function. However, it is possible for the second fluid to be in movement so as to perform a dynamic storage function.
The structure of the collection box 12 will now be described more specifically in reference to
As already indicated, the collection box 12 comprises a collection plate 38 in which the insertion holes 34 are provided for the passage of the respective ends 30 and 32 of the first and second tubes 18 and 20.
A second fluid F2 distribution plate 46, or second distribution plate 46, is arranged against the collection plate 38 and forms stops for the ends 32 of the second tubes 20. The distribution plate 46 ensures the distribution of the second fluid F2. The second fluid F2 distribution plate 46 thus comprises second openings 78, which jointly delimit the second chamber 44 and into which the ends 32 of the second tubes 20 lead. In addition, the distribution plate 46 of the second fluid F2 comprises first openings 80 for the passage of the ends 30 of the first tubes 18.
Another first fluid F1 distribution plate 50, or first distribution plate 50, is placed against distribution plate 46. The first fluid F1 distribution plate 50 forms stops for the ends 30 of the first tubes 18. The distribution plate 50 ensures the distribution 50 of the first fluid F2. The first fluid F1 distribution plate 50 simultaneously delimits the first chamber 42. The distribution plate 50 of the first fluid F1 thus comprises openings 82 that jointly delimit the first chamber 42 and into which the ends 30 of the first tubes 18 lead.
The first fluid F1 distribution plate 50 is superimposed by a closing assembly 52 arranged against the first distribution plate 50 of the first fluid F1. The lid assembly 52 is arranged opposite the distribution plate 46 of the second fluid F2.
According to the example shown, the closing assembly 52 includes an intermediate plate 54 and a lid 56.
This arrangement is such that the first tubes 18 communicate with the first chamber 42, while the second tubes 20 communicate with the second chamber 44. This enables fluid communication to be ensured in every case.
The structure of the collection box 12 can be better understood by considering the exploded view of
The collecting plate 38 comprises two longitudinal raised edges 58 equipped with clamping tabs 60 suitable for being folded back against the respective peripheral edges of the lid 56 in order to hold all of the elements forming the collection box 12 mutually clamped.
The inlet 26 and outlet 28 manifolds respectively define a first inlet and a first outlet for the first fluid F1. The inlet 26 and outlet 28 manifolds communicate with the first chamber 42 of the collection box 12 through the collecting plate 38 and the first fluid F1 distribution plate 46.
Alternatively, according to another embodiment, it is possible for the inlet 26 and outlet 28 manifolds to be arranged respectively in collection box 12 and collection box 14.
According to this embodiment, the first inlet 26 and the first outlet 28 are arranged on the same collection box 12 and they communicate with the first chamber 42 of the collection box 12 through openings 62 and 64 arranged in the collecting plate 38 and through openings 66 and 68 of the first fluid F1 distribution plate 46.
In addition, the collection boxes 12 and 14 respectively have a second inlet 70 and a second outlet 72, shown in
According to the example embodiment, the second inlet 70 and the second outlet 72 are respectively arranged in the collecting plates 38 and 40. The second inlet 70 and the second outlet 72 are holes that will then be closed so as to enable immobilization of the second fluid, which is an immobile fluid as already described.
The inlet opening 74 leads into a longitudinal channel 76 supplying the second openings 78 so as to jointly define the second chamber 44. In a particularly advantageous manner, the longitudinal channel 76 is arranged in the central portion of the second fluid F2 distribution plate 46. The longitudinal channel 76 constitutes an axis of symmetry of the second fluid F2 distribution plate 46. Such an arrangement enables the second openings 78 to be arranged on either side of the longitudinal channel 76.
The second openings 78 are arranged so as to alternate with the first openings 80 through which the ends 30 of the first tubes 18 pass.
Advantageously, the first and second openings 80 and are openings of which the shape corresponds respectively to the cross-section of the first and second tubes 18 and 20. According to the example embodiment, the first and second openings 80 and 78 have an oblong shape. Preferably, the first and second openings 80 and 78 are arranged according to two parallel rows.
The second fluid F2 distribution plate 84 of collection box 14 has a structure similar to that of the second fluid F2 distribution plate 46 of collection box 12. It also includes an opening 88 that supplies a longitudinal channel 90 supplying second openings 92 so as to define a second chamber.
In a particularly advantageous manner, the longitudinal channel 90 is arranged in the central portion of the second fluid F2 distribution plate 84. The longitudinal channel 90 constitutes an axis of symmetry of the second fluid F2 distribution plate 84. Such an arrangement enables the second openings 78 to be arranged on either side of the longitudinal channel 76.
The second openings 92 are arranged so as to alternate with the first openings 94 for the first fluid F1, through which the ends 30 of the first tubes 18 pass.
As in
The first distribution plate 86, shown in
The openings 92, 94 and 98 of the second fluid F2 distribution plate 84 and the first fluid F1 distribution plate 86 are openings of which the shape corresponds respectively to the cross-section of the first tubes 18 and the second tubes 20. According to the example embodiment, the openings 92, 94 and 98 have an oblong shape.
The intermediate plate 54 and the lid 56, as shown in
The collection box 14 includes similar arrangements. Owing to these arrangements, the first fluid F1 is enabled to circulate in a first layer according to a U-path, then in a second layer according to a second U-path, as is well known in the field of evaporators.
a to 8d show the various steps of assembling a heat exchanger 10 according to this invention.
In a first step, the core 16 is formed by positioning a first series of first tubes 18 (
In a second step, a first series of second tubes 20 are positioned, of which the ends have previously been curved so as to be offset with respect to the body of the second tube 20 (
The third step consists of placing the corrugated spacers 24 between two adjacent modules 22 (
In the fourth step, the core is compressed in the direction of the stack so that the ends 30 and 32 of the tubes 18 and 20 are spaced apart by the desired pitch P, i.e. corresponding to the pitch of the insertion holes 34 of the two collection boxes 12 and 14.
Finally, in a fifth step (
According to the assembly method described above, the two rows of modules 22 are mounted simultaneously and a single spacer 24 is inserted between two adjacent modules 22 in the direction of the thickness of the core 16, i.e. the direction of the fluid F3.
Alternatively, it is possible to create two half-cores corresponding to each of the rows of tubes 18 and 20. In this case, the corrugated spacer 24 is interrupted. It is thus possible to create a first half-core, which will be joined to a second similar half-core in order to define the heat exchanger 10. Such a method is particularly advantageous if the collection boxes 12 and 14 are formed in two parts.
The various components of the heat exchanger 10 are advantageously made of aluminum or an aluminum-based alloy so as to enable the assembly thereof by brazing in a single operation in a suitable brazing oven.
The structure of the collection boxes 12 and 14, obtained by assembling a plurality of superimposed plates, enables high resistance to be provided in particular when the refrigerant is a CO2-type fluid, which operates in a supercritical cycle at high pressures, on the order of 150 bars. It is indeed necessary for the various components to be capable of resisting high bursting pressures, on the order of 300 bars.
In the example above, the fluid can be a supercritical fluid, in particular carbon dioxide (CO2) also known as R744, or a sub-critical fluid, in particular a fluorinated compound, in particular the coolant referenced R134a. In addition, this invention can be used with other alternative fluids.
Moreover, this structure makes it possible to maintain an overall profile similar to that of comparable evaporators of the prior art.
As shown in
Of course, the structure of the tube will each time be adapted to the corresponding fluid type. Preferably, tubes with an oblong cross-section having two opposite flat faces enabling the corrugated spacers to be brazed will be used.
When the heat exchanger of the invention is a storage evaporator for a second fluid constituting an accumulation fluid, advantageously having a melting point of between 0 and 10° C., preferably between 4 and 8° C., the second fluid advantageously has a melting enthalpy of at least 150 kJ/kg. The second fluid can advantageously be chosen from tetradecane, paraffins, hydrated salts and eutectic mixtures.
The invention is not limited to the particular use in a storage evaporator as described specifically as an example. It applies to other types of heat exchangers, in particular heating radiators for motor vehicle interiors.
Moreover, the example described above is a heat exchanger equipped with two collection boxes. It is possible to envisage a heat exchanger equipped with a single collection box associated with so-called U-fluid circulation tubes. When multiple rows of tubes are provided in the core, the circulation can occur in a U-form, i.e. the circulation of the fluid entering two tubes opposite one another occurs in opposite directions, or in an I-form, i.e. the circulation of the fluid in two tubes opposite one another occurs in the same direction.
Of course, the invention is not limited to the embodiments described above and provided solely as an example, and encompasses other alternatives that a person skilled in the art may consider in the context of the claims and in particular any combination of the various embodiments described above.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR 09/00331 | Jan 2009 | FR | national |
