EP1992891A1 - Condenser, in particular for an automobile air-conditioning circuit, and circuit comprising such a condenser - Google Patents

Abstract

The condenser for a motor vehicle air conditioning circuit has stacked plates (2) each with a raised peripheral lip (3) which are assembled and sealed to form multiple fluid passages between the plates for a refrigerating fluid (F2) and a coolant (F1). The plates have connecting passages (124) to allow the fluid to pass between the channels. Annular ducts (122) are provided opposite the passages to prevent mixing of the fluids.

Description

The invention relates to air conditioning circuits of motor vehicles.

Modern motor vehicles are frequently equipped with an air conditioning circuit of their cabin. These circuits include in particular a condenser, in which an air conditioning fluid in the gaseous state is cooled so as to be condensed.

In this field it is also known to use air conditioning fluids, such as CO ₂ , with which the circuit can operate without them changing phase. The circuit is then equipped with a heat exchanger to lower their temperature, without going to condense them.

The invention relates as well to a condenser itself as to such exchangers. In order not to burden the rest of the text, only the term condenser will be used. However, it should be understood that it covers both a heat exchanger intended to allow the condensation of a fluid, a heat exchanger designed to allow a simple cooling of the fluid of an air conditioning circuit of a motor vehicle.

The currently known condensers generally consist of a bundle of tubes connected at each of their ends to manifolds. The tubes are provided with heat exchange surfaces such as fins or corrugated inserts. They are cooled by heat exchange with atmospheric air and, for this purpose, they are placed at the front of the motor vehicle, usually in front of the radiator of the engine cooling circuit.

These known condensers have several disadvantages. They do not allow heat exchange on the water of the engine cooling circuit. Their frontal surface, and therefore their size, are important. In addition, they must necessarily be placed on the front of the motor vehicle in order to be effectively cooled.

It is also known to provide condensers consisting of a multiplicity of stacked common plates, assembled to define first flow channels for a refrigerating fluid that alternate with second flow channels for a cooling fluid. A condenser of this type is described in the document WO 01/88454 .

Thanks to these characteristics, such a condenser can be cooled by a liquid, in particular by the liquid of the engine cooling circuit. It is more compact than an air-cooled condenser, it is not necessary to have it on the front of the vehicle. It can therefore be placed near the evaporator, which makes it possible to shorten the length of the pipes of the air conditioning circuit. But a condenser of this type also has drawbacks, in particular, it does not ensure a sufficient heat exchange.

The invention relates to a condenser, in particular for an air conditioning circuit of the passenger compartment of a motor vehicle, which overcomes these disadvantages. This condenser must allow improved cooling of the air conditioning fluid of the air conditioning circuit by the water of the engine cooling circuit.

For this purpose, it proposes a condenser of the type defined above which comprises at least two passes on the refrigeration fluid.

By "pass" is meant a group or subgroup of plates between which the fluid follows a single direction in one and the same direction. For the plates of the same pass the inlet and outlet ports are located, in particular, at two opposite edges of said plates. When passing from one pass to the other, the direction of circulation of the fluid is reversed. It is thus possible to lengthen the path of the fluid in the exchanger. Thanks to these characteristics, the condenser according to the invention has improved performance.

The condenser is constituted by a stack of common plates. An end plate is disposed at each end of the stack of the current plates.

The plates have communication passages to allow the passage of the refrigerant fluid and the cooling fluid from one flow channel to the other, annular conduits are provided alternately opposite the communication passages to prohibit the mixing of the fluids .

Preferably, the current plates are provided with two communication passages for the passage of the cooling fluid and two communication passages for the passage of the cooling fluid. Thus, each current plate has a total of four communication passages.

In a particular embodiment, the plates are provided with raised peripheral edges, assembled in a sealed manner to delimit the first flow channels and the second flow channels.

In another particular embodiment, the condenser comprises at least two passes on the cooling fluid.

Advantageously, the condenser comprises at least one inlet and a refrigeration fluid outlet and at least one pass on the refrigerating fluid communicating with said input, said input pass, and another pass communicating with said output, said output pass, the pass section decreasing since the pass entry to the exit pass.

In the known type of exchangers, the passes are carried out either by partition walls disposed in the manifolds of the tube exchangers, or by spacers arranged between the plates of stacked plate heat exchangers. On the contrary, in the condenser of the invention, fluid flow passes can be made without adding additional parts. It suffices for this to remove certain communication passages provided in the current plates. For this purpose, a communication passage of the refrigeration fluid, respectively a communication passage of the cooling fluid, is removed in some common plates to determine passes for the circulation of the refrigerant fluid, respectively for the circulation of the cooling fluid.

As already indicated, in one embodiment of the invention, the pass section decreases from the pass communicating with the inlet of the condenser, said input pass, to the pass communicating with the output of said condenser, said output pass .

The condenser according to the invention may comprise at least three passes, the number of channels allocated to the input pass on the number of channels allocated to the output channel being comprised, for example, between 2 and 5, the section of channels being scheduled constant from one channel to another.

Advantageously, the plates of the condenser are distributed in a first series to ensure cooling of the refrigeration fluid until its condensation, and in a second series for cooling the cooling fluid below its condensation temperature (subcooling).

Advantageously, the condenser of the invention comprises an integrated bottle between the first and the second series of plates.

In order to improve the heat exchange between the fluids, flow-disrupting elements, called turbulators, may be provided. In a variant, the turbulators are arranged between the plates. In another variant, the plates themselves comprise reliefs which constitute turbulators.

Preferably, the hydraulic diameter of the circulation channels is between 0.1 mm and 3 mm. It may, in particular, be 0.1 to 0.5 mm for fluids intended to not change phase, except exceptional conditions, and 0.5 to 3 mm for fluids intended to be condensed. It will be, for example, from 1 to 2.6 mm for the cooling fluid, which may be water, especially that of the cooling circuit.

Finally, the annular ducts are advantageously constituted by cups formed in the plates. Thus collectors are defined without having to provide any additional room.

Preferably, the cooling fluid is constituted by the water of the cooling circuit of the engine of the motor vehicle.

Furthermore, the invention relates to an air conditioning circuit, in particular for the passenger compartment of a motor vehicle, comprising an evaporator, a compressor, a condenser, an expansion valve, in which a cooling fluid circulates, in which the condenser is in accordance with the present invention.

• la Figure 1 est une vue en coupe d'un condenseur conforme à l'invention ;
• la Figure 2 est une vue en coupe d'un condenseur conforme à l'invention, comportant deux passes sur le fluide de réfrigération ;
• la Figure 3 est une vue schématique en perspective d'un condenseur conforme à l'invention, comportant trois passes sur le fluide de réfrigération et une passe sur le liquide de refroidissement ;
• la Figure 4 est une vue schématique en perspective d'un condenseur conforme à l'invention, comportant deux passes sur le fluide de réfrigération et deux passes sur le liquide de refroidissement ;
• la Figure 5 est une vue éclatée en perspective d'un échangeur à deux passes sur le fluide de réfrigération et à deux passes sur le fluide de refroidissement qui illustre la circulation de ces deux fluides ;
• la Figure 6 est une vue extérieure en perspective d'un condenseur conforme à l'invention, comportant une bouteille intégrée ;
• la Figure 7 est une vue de gauche du condenseur représenté sur la Figure 6 ;
• la Figure 8 est une vue en coupe transversale du condenseur représenté sur les Figures 6 et 7 ;
• la Figure 9 est une vue en coupe par un plan passant par l'axe longitudinal de la bouteille du condenseur des Figures 6 à 8 ;
• la Figure 10 représente un premier mode de réalisation d'un élément turbulateur inséré entre les plaques ;
• la Figure 11 représente une autre forme de réalisation d'un élément turbulateur inséré entre les plaques ;
• la Figure 12 représente des turbulateurs rectilignes ondulés issus de reliefs formés dans les plaques ;
• la Figure 13 représente des turbulateurs en chevrons issus de reliefs formés dans les plaques ; et
• la Figure 14 représente un condenseur à trois passes conforme à l'invention.

Other features and advantages of the invention will become apparent on reading the following description of exemplary embodiments given by way of illustration with reference to the appended figures. In these figures:

• the Figure 1 is a sectional view of a condenser according to the invention;
• the Figure 2 is a sectional view of a condenser according to the invention, comprising two passes on the refrigerant fluid;
• the Figure 3 is a schematic perspective view of a condenser according to the invention, comprising three passes on the refrigerant fluid and a pass on the coolant;
• the Figure 4 is a schematic perspective view of a condenser according to the invention, comprising two passes on the refrigerant fluid and two passes on the coolant;
• the Figure 5 is an exploded perspective view of a two-pass heat exchanger on the refrigerant fluid and two passes on the cooling fluid which illustrates the flow of these two fluids;
• the Figure 6 is an external perspective view of a condenser according to the invention, comprising an integrated bottle;
• the Figure 7 is a left view of the condenser shown on the Figure 6 ;
• the Figure 8 is a cross-sectional view of the condenser shown in Figures 6 and 7 ;
• the Figure 9 is a sectional view through a plane passing through the longitudinal axis of the condenser bottle of Figures 6 to 8 ;
• the Figure 10 represents a first embodiment of a turbulator element inserted between the plates;
• the Figure 11 represents another embodiment of a turbulator element inserted between the plates;
• the Figure 12 represents corrugated rectilinear turbulators derived from reliefs formed in the plates;
• the Figure 13 represents turbulators in chevrons resulting from reliefs formed in the plates; and
• the Figure 14 represents a three-pass condenser according to the invention.

We have shown on the Figure 1 a cross-sectional view of a condenser according to the present invention. It comprises a multiplicity of common plates 2 stacked one on the other and each provided with a peripheral rim 3. The peripheral edges are assembled in a sealed manner to delimit between the plates 2 of first flow channels for a refrigeration fluid F1 which alternate with second flow channels for a cooling fluid F2. The stack of the common plates has an end plate 6 at each of its ends.

In order to reinforce the resistance of the condenser to pressure, the common plates 2 are sandwiched between a lower reinforcement plate 8 and an upper reinforcement plate 10. The refrigeration or air-conditioning fluid F1 enters the condenser through a pipe of entry (not shown on the Figure 5 ) and exits through an outlet pipe 14. The cooling fluid F2 enters the condenser through an inlet pipe 20 and out through an outlet pipe (not shown). The refrigerating fluid F1 enters the gaseous state. It circulates in the first channels by exchanging heat with the cooling fluid F2, which causes its condensation. The fluid F1 thus leaves the condenser in the liquid state.

The refrigeration or air-conditioning fluid is, for example, a fluid R134a or R744 (CO ₂ ), while the fluid of cooling F2 is constituted by the water of the engine cooling circuit. It may also be an independent water loop.

The condenser shown on the Figure 2 has two circulation passes for the air conditioning or refrigeration fluid. This fluid enters the tubing 12, as shown by the arrow F1, it enters an annular duct 24 acting as an inlet manifold and, from there, enters the first circulation channels provided between the plates 2 As shown schematically by the arrow 26. After having traversed the entire heat exchange surface, the air-conditioning fluid arrives in an annular duct 28 and thence enters the first circulation channels provided between the plates 2 situated below. of the partition wall 30, as represented by the arrow 32. It crosses a second time the exchanger, from right to left, in a second pass, to reach the lower portion 34 of the annular conduit acting as a box outlet manifold, as shown schematically by the arrow 36, and leaves the condenser through the outlet pipe 14, as shown schematically by the arrow 38.

As can be seen on the Figure 3 which represents a perspective view of a condenser according to the invention, the refrigeration fluid F1 and the cooling fluid F2 do not necessarily travel through the condenser with the same number of passes. In the example shown, the condenser comprises three passes schematized by the arrows 40, 42 and 44 for the refrigerating fluid, and a single pass schematized by the arrow 48 for the cooling fluid F2. The fluid F1 passes from the first pass to the second after having crossed the passage opening 50, then from the second pass 42 to the third pass 44 after having crossed the communication passage 52. It exits the exchanger through the tubing 14. The cooling fluid F2 enters through the inlet pipe 20, travels the heat exchanger in a single pass 48 and leaves the condenser through the outlet pipe 22.

On the Figure 4 , the condenser has two circulation passes for the refrigerant fluid and two passes also for the cooling fluid. The refrigerating fluid F1 enters the condenser through the inlet pipe 12, traverses the plates along the first pass 54, crosses the communication passage 56 and passes through the second pass 58 before emerging through the outlet pipe 14. The fluid cooling F2 enters the condenser through the inlet pipe 20, travels the first pass as shown by the arrow 60, crosses the communication passage 62 before going through the second pass 64. It then emerges from the exchanger through the tubing output 24.

Diagrammatically shown on the Figure 5 an exploded perspective view illustrating the flow of fluids in a condenser according to the invention comprising two circulation passes for the air conditioning fluid F1 and two passes for the cooling fluid F2. The fluid F1 enters the upper part of the exchanger through the inlet pipe 12 in the volume defined by the end plate 6 and the adjacent plate 2. Part of the fluid travels this space from left to right according to the Figure 5 , as shown schematically by the arrow 66. The other part of the fluid enters an annular duct 68 disposed between the plates 2a and 2b, as shown schematically by the arrow 70. When leaving the annular duct, it enters the space between the plates 2b and 2c. The fraction of the fluid that has passed through the space between the end plate 6 and the first current plate 2a emerges from this space through a tubular duct 72 disposed between the plates 2a and 2b.

The planar space between the plates 2b and 2c comprises only one communication passage 74 allowing the exit of the fluid F2. This fluid passes through the annular passage 76 to reach between the plates 2d and 2e after undergoing a change of direction of circulation. It traverses indeed this space from right to left, whereas it circulated previously from left to right.

In the same way, the cooling fluid F2 which enters the condenser through an inlet manifold (not shown) located at the lower part of the exchanger circulates from left to right in the planar spaces between two successive plates. It passes from a space between two plates to the next space, these spaces alternating with spaces for the fluid F1 by annular conduits similar to the ducts 70 or 76 mentioned above. Arrived in the space between the plates 2e and 2f, as shown schematically by the arrow 80, the fluid F2 enters the annular duct 82, as shown schematically by the arrow 84, and changes direction of circulation. In the upper part of the condenser, it circulates from right to left as it circulated from left to right in the lower part. A second flow pass is thus made for the fluid F2 as well.

It will thus be noted that the condenser of the invention comprises three different types of plates with regard to the number of communication passages. The end plates, like the plate 6, have only two communication passages, the first for the entry of one of the fluids, the second for the outlet of the other fluid. Common plates, such as plate 2f, have four communication passages. Two of these passages are dedicated to the first fluid F1, while the other two passages are dedicated to the fluid F2. The plates located just before the end plate 6, like the plate 2a, have three communication passages instead of four for the current plate. The plate 2d, which makes it possible to make the circulation passes of the two fluids, comprises only two communication passages. Indeed, in removing two of the four communication passages, partitions are made to change the flow direction of the fluid. The plates 2c and 2e, adjacent to the plate 2d, have three communication passages, instead of four for the current plates. There are thus three types of plates. The two end plates and the plate 2d have only two passages. The plates adjacent to the end plates and the plate 2d have three passages, while the current plates of the condenser comprise four.

To the Figure 14 it is found that the condenser according to the invention may comprise at least three passes "a", "b" and "c". The number of channels assigned to the input pass "a", ie the pass communicating with the refrigerant inlet in the condenser, on the number of channels assigned to the exit pass "c" , that is to say the pass communicating with the refrigeration fluid outlet out of the condenser, is between 2 and 5, the section of the channels being constant from one pass to another.

In the case of a three-pass condenser it will be possible, as an illustrative example, to have 15 to 20 channels in the input pass "a", 8 to 10 channels in the intermediate pass "b" and 4 to 7 channels in the exit pass "c". In the example of the Figure 14 , the numbers of these channels are respectively N1 = 17 for the pass "a", N2 = 10 for the pass "b" and N3 = 6 for the pass "c", hence a ratio N1 / N3 = 17/6 = 2.83.

We have shown on Figures 6 and 7 , respectively, a sectional view and a left view of a second embodiment of a condenser according to the present invention. It is distinguished by the fact that its plates are divided into a first series 94 and a second series 96 separated from each other by a frame 98 in which is housed a bottle 100. The first series of plates 94 is relatively more important than the second series 96. It is preferably located at the top of the exchanger, while the second series is located at the bottom.

The plates of the first series constitute a cooling section of the refrigeration fluid and the plates of the second series constitute a subcooling section of this fluid. The bottle 100, also called intermediate tank, ensures the filtration and dehydration of the refrigerant. It also makes it possible to compensate for these variations in volume and to ensure the separation of the liquid and gaseous phases. Its interposition between an upstream part and a downstream part 96 of the condenser makes it possible to circulate only fluid in the liquid state in the subcooling section. The refrigeration fluid is thus cooled below its liquid-gas equilibrium temperature, which improves the performance of the condenser and makes them relatively independent of the amount of fluid contained in the air conditioning circuit.

The circulation of the refrigerating fluid, as well as the circulation of the cooling fluid, can be carried out in one or more passes in the cooling section 94, as well as in the subcooling section 16. The refrigerating fluid F1 enters the cooling zone. cooling section 94 through the inlet pipe 12 located in the upper part of the condenser. It traverses the cooling section, in one or more passes, then passes into the bottle 100, in which it is filtered and dehydrated, then returns to the subcooling section 96 before leaving the exchanger through the outlet pipe 14 .

The cooling fluid F2 circulates against the current of the refrigeration fluid. It enters the lower part of the condenser, in the subcooling section 96, by the inlet tubing 20 (see Figure 7 ), it passes through the subcooling section 96 and then enters directly into the cooling section 94 before emerging from the condenser through the outlet pipe 22. As can be seen more particularly on the Figure 7 the frame 98 comprises two flanges 102 and a central portion 103 in which three cylindrical bores 104 are formed which constitute the bottle. One of these bores, the one on the right on the Figure 7 , receives a filter and desiccant salts. The plates of the first series 94 and the second series 96 bear on the flanges 102 of the frame 98. It will also be noted that in this example, their concavities are opposite.

We have shown on Figures 8 and 9 , respectively, a longitudinal sectional view of the condenser passing through the longitudinal axis of the portion of the bottle 100 comprising the filter and the desicative salts and a cross section of the same exchanger. The corresponding cylindrical bore 104 is extended by a cylindrical portion 106 projecting out of the condenser. This cylindrical portion receives a cap 108 having a hexagonal head 110 which closes the bottle. The plug 108 is provided with a toric seal 112. An elongated cylindrical cartridge 114 is housed inside the cylindrical bore 104. It contains the desiccant 116 which makes it possible to dehydrate and filter the refrigerating fluid F1. .

The Figure 9 allows to appreciate the particular shape of the plates 2 of the condenser. Each plate comprises a flat-bottom half-bowl 122 crossed by a through hole 124. When the plates of the exchanger are stacked, the flat bottoms of the cups come into contact with one another. During the brazing operation of the exchanger, they are assembled together in a sealed manner. Advantageously, annular ducts are produced which permit the circulation of the refrigeration fluid F1 and the fluid of cooling F2 from one passage channel to another without having to use additional pieces arranged between the plates. Of course, as an alternative embodiment, one plate out of two could be flat, the bowl formed in the adjacent plate having a depth corresponding to the entire spacing between two successive plates.

In addition, according to the invention, turbulators (also called disrupters) for improving the heat exchange can be arranged between the plates. We have shown on the Figure 10 a first embodiment of a turbulator element 132. It is constituted by a stamped sheet shaped so as to have rectilinear corrugations 134 arranged, for example, in the direction of the length of the plates. In this case, the plates 2 have a generally flat bottom.

We have shown on the Figure 11 another embodiment of a turbulator element 136. It comprises stampings 138 having the general shape of crenellations. These slots are divided into two series offset with respect to each other. Such a turbulator element 136 is disposed between plates 2 also having a generally flat bottom.

The turbulators 132 and 136 shown in the Figures 10 and 11 require to manufacture an additional piece and to insert it between the plates. It is possible to remove this additional piece by making the turbulators elements by reliefs from the plates themselves and obtained by a stamping operation.

So, on the Figure 12 the condenser comprises first plates 140 each having a bottom 142 having corrugations 144 defined by generatrices extending in a first direction D1 and second plates 146 arranged alternately with the first plates 140 and having each having a bottom 148 having undulations 150 defined by generatrices extending in a second direction D2 which is substantially perpendicular to the first direction D1. The respective undulations of the plates make it possible to give the channels a particular three-dimensional structure which favors a turbulent flow of the fluid F1 and the fluid F2 and, consequently, a good heat exchange between them. This also eliminates turbulators inserted between the plates.

We have shown on the Figure 13 an alternative embodiment of the turbulators of the Figure 12 . The exchanger comprises a first series of plates 154 and a second series of plates 156 respectively comprising corrugations 158 and 160 in the form of chevrons. These corrugations also define a three-dimensional structure of fluid flow channels that promotes turbulent flow and good heat exchange between them.

Claims (14)

Condenser, in particular for a motor vehicle air conditioning circuit comprising a multiplicity of stacked common plates (2) assembled to define first flow channels for a refrigerating fluid (F1) which alternate with second flow channels for a fluid cooling device (F2), characterized in that the plates (2) are distributed in a first series (94) for cooling the cooling fluid to its condensation and in a second series (96) for cooling the refrigerant. refrigeration fluid below its condensation temperature. Condenser according to claim 1, characterized in that it comprises a bottle (100) integrated between the first and the second series of plates (94, 96). Condenser according to Claim 1 or 2, characterized in that it comprises at least two passes on the refrigeration fluid. Condenser according to any one of the preceding claims, characterized in that the plates comprise communication passages (124) for allowing the passage of the refrigerating fluid (F1) and the cooling fluid (F2) of a flow channel to the other, annular conduits (68, 122) are provided alternately opposite communication passages to prohibit the mixing of the fluids. Condenser according to any one of the preceding claims, characterized in that the current plates are provided with two communication passages for the passage of the refrigerating fluid (F1) and two communication passages for the passage of the cooling fluid (F2). . Condenser according to any one of the preceding claims, characterized in that the stacked plates (2) are provided with raised peripheral edges (3), assembled in a sealed manner. Condenser according to any one of the preceding claims, characterized in that it comprises at least one inlet and one outlet of refrigeration fluid and at least one pass (a) on the refrigerating fluid communicating with said inlet, referred to as a pass. input, and another pass (c) communicating with said output, said output pass, the pass section decreasing from the input pass to the output pass. Condenser according to any one of the preceding claims, characterized in that a communication passage of the refrigeration fluid, or a communication passage of the cooling fluid, is removed in certain common plates to determine passes for the circulation of the cooling fluid. refrigeration, respectively for the circulation of the cooling fluid. Condenser according to one of Claims 1 to 8, characterized in that turbulators (132, 136) are arranged between the plates (2). Condenser according to one of claims 1 to 8, characterized in that the plates comprise reliefs (144, 150, 158, 160) which constitute turbulators. Condenser according to one of claims 1 to 10, characterized in that the hydraulic diameter of the fluid flow channels (F1 and F2) is between 0.1 mm and 3 mm. Condenser according to one of Claims 3 to 11, characterized in that the annular ducts consist of cups (122) formed in the plates (2). Condenser according to one of claims 1 to 12, characterized in that the cooling fluid (F2) is constituted by the water of the engine cooling circuit of the motor vehicle. Air conditioning circuit, particularly for the passenger compartment of a motor vehicle, comprising an evaporator, a compressor, a condenser, in which a refrigerating fluid circulates, characterized in that the condenser is in accordance with one of the claims 1 to 13 .

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