FR3000188A1 - THERMAL EXCHANGE ELEMENT AND CORRESPONDING HEAT EXCHANGER - Google Patents

Abstract

The invention relates to a heat exchange element (3) comprising at least two plates (29) assembled, said plates (29) respectively having at least one circulation channel (31) of the first fluid and at least one reservoir (33). a thermal storage material. According to the invention, the heat exchange element (3) further comprises at least one inner fin (39) arranged between said two plates (29). The invention also relates to a heat exchanger comprising a beam provided with at least one such heat exchange element (3).

Description

The invention relates to a heat exchanger between at least a first fluid and a second fluid, for example used in the automotive field and more particularly to a heat exchanger comprising a plurality of channels for to the circulation of the first fluid. The invention relates in particular to a heat exchange element of a heat exchanger. A heat exchanger has the function of ensuring a heat exchange between a first fluid circulating inside a plurality of channels and an external fluid passing through the heat exchanger. In the case of a motor vehicle air-conditioning system, the external fluid may be a gaseous flow such as air intended to be blown into the passenger compartment of the vehicle. The heat exchange allows to refresh the air blown. The channels conventionally open into collectors whose function is notably to allow fluid communication between all the channels or part of this plurality of channels. The heat exchanger is connected to the remainder of a fluid circulation circuit, for example an air conditioning circuit for a motor vehicle. The circulation of the fluid inside the circuit is provided by a compressor driven directly by the engine 20 of the motor vehicle. Therefore, when the engine of the vehicle is stopped, the circulation of the fluid in the circuit no longer takes place, and the heat exchange between the air and the first fluid can not operate. The air blown into the passenger compartment of the vehicle is then no longer refreshed. This situation is all the more problematic since recent fuel saving systems provide for the automatic stopping of the engine when the car comes to a standstill, frequently depriving the passenger compartment of cooled air.

It is known to provide a heat exchanger of thermal storage material tanks for a heat exchange between the first fluid and the thermal storage material. The first fluid may be a refrigerant. And, the thermal storage material may be a frigory storage material. In addition, it can take the form of a solid material, liquid, or phase change known under the acronym PCM for English "Phase Change Material". Thus, when the engine of the vehicle is running, the coolant cools both the air passing through the heat exchanger and the thermal storage material. The thermal storage material restores the cold (more precisely frigories) to the air passing through the heat exchanger when the engine is shut down. According to a known solution, the bundle of the heat exchanger comprises a plurality of heat exchange elements, which may also be called tubes, formed of at least a first plate and a second plate also called cooling plates, and a separating plate interposed between the first and second refrigerant plates. The first and second refrigerant plates respectively have at least one circulation channel of a first fluid and at least one reservoir of the thermal storage material. The partition plate has a plurality of orifices 20 for communicating the circulation channel or channels of the first plate respectively with a channel of the second plate, or to put in communication the tanks of the two plates. However, the assembly of the two refrigerating plates and the separating plate increases the thickness of the tube with respect to a conventional evaporator, in particular about 20%, which increases the pressure drop on the air. In addition, the circulation channels may have oscillations and the two refrigerant plates may be arranged in opposition, so that the oscillations of the channels of the two plates are in phase opposition. Such a design leads to a non-homogeneous pressure distribution within the tube. This imposes an important material thickness for the components such as the separating plate. In addition, the filling of the storage material can be achieved by means of at least one orifice supplying a central tank and a plurality of additional holes, for example oblong, are arranged on the separating plate in overlap with lateral tanks of the two. refrigerant plates so that the filling of the central tank ensures the filling of the side tanks of the two plates. To increase the performance of the heat exchanger, the refrigerant hydraulic sections should be increased. However, due to the one-point filling of the reservoirs with the thermal storage material, each heat exchanger element 15 has covering areas of the tanks to the right of which the separating plate comprises oblong holes. Such a constraint consequently prevents the refrigerant hydraulic section necessary to increase the thermal performance of the exchanger to be increased. According to another known solution, the heat exchange elements are respectively formed by assembling a pair of plates. Each plate respectively comprising at least one circulation channel of the first fluid and at least one reservoir of a thermal storage material for a heat exchange between the first fluid and the thermal storage material. In particular, it is known that the plates respectively have two external flow channels of the first fluid and an intermediate reservoir of a thermal storage material arranged between the two circulation channels. The channels and tanks are for example made by stamping and extend substantially rectilinear manner.

However, such a heat exchanger may not achieve a certain level of performance required by car manufacturers. To meet such a requirement, one of the known solutions of the prior art proposes to have excrescences on the channels intended for the circulation of the first fluid. However, this solution may not be optimal in terms of performance. In addition, the location of the three compartments, two for the first fluid and one for the central storage material associated with the drawing height, prevents material thickness reduction beyond a certain value thus limiting the reductions. 10 weight, bulk and cost. The invention therefore aims to provide a heat exchanger with improved performance at least partially overcomes the disadvantages of the prior art. For this purpose, the subject of the invention is a heat exchange element comprising at least two assembled plates, said plates respectively having at least one circulation channel of the first fluid and at least one reservoir of a thermal storage material, characterized in that the heat exchange element further comprises at least one inner fin arranged between said two plates. Thus, the presence of the internal fin between the two plates provides a mechanical strength to the two plates on either side of the inner fin to reduce the thickness of the plates forming the heat exchange element. This fin promotes the freezing of the thermal storage material in the reservoirs of the plates. The arrangement of the inner fin between the two plates forming the heat exchanger thus makes it possible to improve the performance of the heat exchanger.

Said heat exchange element may further comprise one or more of the following characteristics, taken separately or in combination: said at least one fin is soldered to the two plates on either side of the fin; said plates respectively have two circulation channels of the first fluid and an intermediate reservoir of a thermal storage material arranged between the two circulation channels; said at least one fin has two outer portions respectively arranged vis-à-vis the circulation channels of the two plates and a central portion arranged vis-à-vis the tanks; said at least one fin is substantially corrugated; said outer and central portions of said at least one fin are substantially corrugated and said at least one fin comprises substantially planar separation portions between said corrugated portions; said heat exchange element has sealing junction zones between two traffic channels vis-à-vis the two plates and two tanks opposite the two plates; the channels for the circulation of the first fluid and the tanks for receiving the thermal storage material of said plates are made by stamping. The invention also relates to a heat exchanger between at least first and second fluids, comprising a beam provided with at least one heat exchange element as defined above. According to one aspect of the invention, said exchanger is used as an evaporator in an air conditioning circuit. Other features and advantages of the invention will emerge more clearly on reading the following description, given by way of illustrative and non-limiting example, and the appended drawings in which: FIG. 1 is a perspective view of 1 is a partially exploded view of the heat exchanger of FIG. 1; FIG. 3 is a perspective view of a spacer of the heat exchanger of FIG. 1; FIG. 4a is an exploded perspective view of a heat exchange element of the heat exchanger of FIG. 1; FIG. 4b is a partially assembled view of the heat exchange element of FIG. FIG. 5 is a perspective view of an internal fin of the heat exchange member of FIGS. 4a and 4b, and FIG. 6 is a sectional view of the heat exchange element of FIGS. Figures 4a and 4b. In these figures, the substantially identical elements bear the same references. Figure 1 is a schematic view of a heat exchanger according to the invention. This heat exchanger can be used in particular as an evaporator of an air conditioning circuit of a motor vehicle.

In operation, the heat exchanger 1 allows a heat exchange between a first fluid, such as a heat transfer fluid, and a second fluid, such as a gas flow such as an air flow passing through the heat exchanger 1, as shown schematically. by the arrow A in FIG.

The heat exchanger 1 allows a circulation of the coolant in one or more passes. According to the example shown in Figure 1, the circulation of the heat transfer fluid is in six passes: P1, P2, P3, P4, P5, P6. The direction of circulation of the heat transfer fluid is shown schematically by arrows. Of course, other circulation of the coolant can be provided, for example a circulation in four passes.

According to the illustrated example, the heat exchanger 1 has a generally parallelepipedal shape. The heat exchanger 1 comprises a bundle of heat exchange elements 3, the latter being intended to contain on the one hand a heat transfer fluid and on the other hand a thermal storage material.

The heat transfer fluid may be a refrigerant, for example R134a. The thermal storage material may be a frigory storage material. In addition, it can take the form of a solid material, liquid, or phase change known under the acronym PCM for English "Phase Change Material". As can be seen in FIGS. 1 and 2, the bundle comprises a successive stack 20 of aligned heat exchange elements 3, such as heat exchange tubes 3. This bundle furthermore has two plates according to the illustrated embodiment. 5 at its longitudinal ends on either side of the heat exchange tubes 3. At least one closure plate 5 has orifices 7 opening into tubings 9 for the supply of heat transfer fluid and the discharge of the fluid. coolant.

In FIG. 1, only one of the closing plates 5 comprises an inlet pipe and an outlet pipe 9. The heat exchanger 1 may further comprise heat exchange pads 21 (see FIG. each time between two heat exchange tubes 3 adjacent. Here, a spacer 21 is each placed in the space left free between two heat exchange tubes 3. The function of the spacer 21 is to increase the heat exchange surface between a thermal storage material, a fluid coolant contained in the heat exchange tubes 3 and a gas flow, such as the air flow A outside through the heat exchanger 1.

The spacers 21 may be formed from a metal strip, for example aluminum alloy. The heat exchange tubes 3 and the spacers 21 may be brazed together. The spacers 21 have for example a generally undulating form.

Referring to Figures 1 and 3, a spacer 21 comprises a predefined number of planar walls 23. The planar walls 23 are substantially rectangular. These flat walls 23 are substantially parallel and are connected in pairs by folds 25. In the case of an interlayer 21 corrugated as in the example shown, the folds 25 are substantially rounded and the flat walls 23 are connected in pairs by folds 25 so as to form alternating corrugations. The spacers 21 may be attached to the exchange tubes 3 by their respective folds, for example by brazing. In addition, the flat walls 23 comprise a plurality of louvers 27 substantially inclined relative to the general plane P defined by the plane walls 23. The louvers 27 can be made by cutting and folding the metal material of the insert 21.

The louvers 27 therefore define openings at a given opening angle, through which the gas flow passes, which increases the heat exchange surface. The louvers 27 create disturbances of the air flow A through the heat exchanger 1, thus promoting heat exchange.

There may be two groups of louvers 27 having a respective orientation. The louvers 27 of the same group may be substantially identical. In addition, these louvers 27 can extend over the entire height of the plane wall 23. Referring to FIGS. 4a, 4b, the heat exchange tube 3 comprises a pair of plates 29. The elements or tubes of heat exchange 3 are connected to each other in fluid communication via junction flanges 30 formed on the end portions of the plates 29. The junction flanges 30 are made from material preferably by stamping so that they respectively form a ring protruding out of the plane of the plate and delimiting an orifice 35. The first and the second plates 29 are in this example substantially rectangular. The first and second plates 29 may be stamped plates. The two stamped plates 29 can be made from metal plates. The two plates 29 respectively comprise at least one channel 31 for the coolant and a reservoir 33 of the thermal storage material. The reservoir 33 is separate from the channel 31 for circulating the coolant. The plates 29 may respectively have a substantially planar zone 34 between the edges of a heat transfer fluid circulation channel 31 and the edges of a reservoir 33.

According to the embodiment described, the plates 29 respectively comprise two channels 31 for the coolant and an intermediate reservoir 33 arranged between the two channels 31. Thus, when heat transfer fluid circulates in the two channels, these two fluid parts are separated by the thermal storage material in the reservoir 33. The channels 31 are for example made by stamping. According to the illustrated example, the channels 31 extend substantially rectilinearly. The channels 31 may be substantially identical. The intermediate reservoir 33 may have the same dimensions as the two channels 31. Similar to the channels 31, the reservoir 33 may extend substantially rectilinearly. The reservoir 33 is arranged in contact with at least one channel 31 for a heat exchange between the storage material and the coolant. The plates 29 have respectively at least two inlet and outlet ports 15 for the coolant. In the illustrated example, a plate 29 has four orifices 35 at the ends of the channels 31. These orifices 35 have, for example, a substantially ovoid shape. The plates 29 furthermore comprise orifices 37, two in the illustrated example, allowing the filling of the thermal storage material of the reservoir 33. Between the first and second plates 29, an inner fin 39 is interposed. This internal fin 39 may be brazed to the plates 29. The inner fin 39 may have corrugations. In this case, the peaks of the corrugations can be brazed respectively to the plates 29. The inner fin 39 must therefore be dimensioned in height so that each peak can be soldered on the plates 29 between which it is arranged. By way of example, the thickness of the fin 39 is between 50 and 100 μm. A heat exchange tube 3 is thus produced in this embodiment by the juxtaposition of two plates 29 and a fin 39 interposed. . The fin 39 has at least a first portion 41 facing a channel 31 for circulating the coolant and at least a second portion 43 vis-à-vis the reservoir 33. According to the illustrated example, the inner fin 39 has three portions: two first external portions 41 facing the channels 31 for circulating the coolant, separated by a second central portion 43 vis-à-vis the reservoir 33. As previously said l internal fin 39 may be corrugated, in this case the inner fin may have corrugations at these portions 41, 43 vis-à-vis the channels 31 or reservoirs 33 of the plates 29, and have substantially planar portions 45 between these parts 41, 43 of fin. These flat portions 45 are arranged substantially facing the plane zones 34 of the plates 29 when the heat exchange tube 3 is assembled.

Of course other variants of embodiment of the inner fin 39 are conceivable. For example, it can be provided that the outer portions 41 of the inner fin 39 are substantially corrugated and that the central portion 43 is substantially flat. The pitch of the corrugations can thus vary according to their location with respect to the tube portions.

According to the embodiment described, the assembled heat exchange tube 3 thus has three distinct parts which are more clearly visible in FIG. 6: two end portions formed by the circulation channels 31 of the plates 29 and the first portions 41 of the internal spacer 39, and a central portion formed by the reservoirs 33 of the plates 29 and the second portion 43 of the internal fin 39 interposed.

The presence of the fin 39 between the channels 31 of the plates 29 and between the reservoirs 33 of thermal storage material makes it possible to improve the heat exchange between the coolant and the thermal storage material. This promotes near-freezing of the thermal storage material, for example a PCM phase change material. The complete freezing of the PCM material is therefore favored.

The heat exchange tube 3 may have connecting zones 47 between these three portions. These connecting zones 47 are formed by the flat zones 34 of the plates 29 Once the first and second plates 29 affixed to either side of the inner fin 39, and assembled for example by brazing, these three portions are separated from each other. waterproof way. Such internal fin 39 provides a mechanical strength to the heat exchange tube 3. The fin 39, for example brazed to the plates 29 on either side of the fin 39, provides a stiffness which prevents the deformation of the plates 29 when the heat exchange tube 3 is subjected to pressure. Above described an inner fin 39 made in one piece. According to a variant not shown, it is possible to provide a plurality of separate internal fins respectively interposed between external circulation channels 31, according to this example, and between the tanks 33 of thermal storage material. 20

Claims (10)

REVENDICATIONS1. Heat exchange element (3) comprising at least two plates (29) assembled, said plates (29) having respectively at least one channel (31) for the circulation (31) of a first fluid and at least one reservoir ( 33) for containing a thermal storage material, characterized in that the heat exchange element (3) further comprises at least one inner fin (39) arranged between said two plates (29). 2. heat exchange element according to claim 1, wherein said at least one fin (39) is brazed to the two plates (29) on either side of the fin (39). 3. heat exchange element according to one of the preceding claims, wherein said plates (29) respectively have two circulation channels (31) of the first fluid and an intermediate reservoir (33) of a thermal storage material arranged between the two traffic channels (31). 4. heat exchange element according to the preceding claim, wherein said at least one fin (39) has two outer portions (41) arranged respectively vis-à-vis the circulation channels (31) of the two plates (29). and a central portion (43) arranged vis-à-vis the tanks (33). 5. Heat exchange element according to one of the preceding claims, wherein said at least one fin (39) is substantially corrugated. A heat exchange element according to claims 5 and 6, wherein said outer (41) and central (43) portions of said at least one fin (39) are substantially corrugated and said at least one fin (39) comprises substantially planar portions (45) between said corrugated portions (41, 43). 7. Heat exchange element according to any one of the preceding claims, having sealed connection areas (47) between two channels of flow (31) vis-à-vis the two plates (29) and d on the other hand two tanks (33) vis-à-vis the two plates (29). 8. heat exchange element according to any one of the preceding claims, wherein the channels (31) for the circulation of the first fluid and the tanks (33) for receiving the thermal storage material of said plates (29) are made by stamping. 9. Heat exchanger (1) between at least first and second fluids, comprising a beam provided with at least one heat exchange element (3) according to any one of the preceding claims. 10. Heat exchanger according to the preceding claim, used as an evaporator in an air conditioning circuit.