FR2727197A1 - COOLING PROCESS AND TWO-CIRCUIT HEAT EXCHANGER - Google Patents

Abstract

Cooling method using two heat transfer fluid circuits which have in common a multiple heat exchanger, the tubes (3) of which are rigidly connected to the collectors (14) of two fluid boxes (1, 2). A first circuit comprises a compartment (4) of a fluid box (1) and the second circuit comprises two compartments (5, 6) of the same fluid box, these compartments being separated by transverse partitions. The downstream compartment (6) of the second circuit is adjacent to the compartment (4) of the first circuit in such a way that, in the operating phases where the coolant circulates in the second circuit and not in the first circuit, the fluid circulating in the tubes of the second circuit closest to those of the first circuit are already cooled by previous passes, which limits the stresses. Application to the cooling circuits of motor vehicles.

Description

Cooling method and two-circuit heat exchanger

  The invention relates to cooling circuits with

  heat exchangers, in particular for motor vehicles

  biles. To cool an internal combustion engine in a vehicle

  automotive, a cooling circuit is conventionally used

  sement suitable for circulating a heat transfer fluid, generally water with antifreeze, through the engine block to take heat energy there and restore it to the outside environment by heat exchange with air in a heat exchanger heat, commonly called

cooling radiator.

  It is also known to use this heat transfer fluid in one or more secondary cooling circuits, in particular for cooling the lubricating oil of the engine or also for cooling the charge air coming from

of a turbo-compressor.

  To limit the size and the cost of all the circuits, FR-A-2 634 546 proposes to use the same radiator there for cooling the heat transfer fluid. This document describes in particular a method of cooling, in particular of the heat engine of a motor vehicle, using at least a first circuit and a second circuit of heat transfer fluid which have in common a multiple heat exchanger comprising a bundle of circulation tubes of heat transfer fluid comprising at least one row of substantially parallel tubes, each tube passing through a perforated wall or manifold of at least one fluid box, this

  the latter being divided by partitions, at least in the vicinity

  swimming of the collector, in several compartments each of which communicates with a subset of the tubes of the row, a first of said compartments belonging to the first circuit and at least two other compartments, among which a second compartment adjacent to the first, belonging to the second circuit in which they are arranged in series by means of circulation tubes, process comprising phases during which the heat transfer fluid circulates simultaneously in the first and second circuits and other phases during which the heat transfer fluid circulates in

  the second circuit and not in the first circuit.

  The first circuit can be used in particular for cooling

  the heat engine, and the second circuit for cooling the charge air, the heat transfer fluid of this second circuit circulating in several passes in the heat exchanger to be brought to a

  lower temperature than that of the first circuit.

  Figure 1 shows schematically a cooling radiator

  Dissement in accordance with the teaching of FR-A-2 634 546. This radiator comprises two fluid boxes 1 and 2 and a bundle of tubes 3. The fluid box 1 is divided by transverse partitions into three successive compartments 4, 5 and 6, two inlet pipes 7 and 8 opening respectively into compartments 4 and 5. The fluid box 2 is similarly divided into three successive compartments 9, 10 and 11, two outlet pipes 12 and 13 opening respectively in compartments 9 and 11. Such a heat exchanger can be mounted in two cooling circuits, namely a cooling circuit of the engine of a motor vehicle in which the heat transfer fluid enters the

  compartment 4 through tubing 7, then goes into the compar-

  9 through the tubes and out through the tubing 12, and a charge air cooling circuit into which the heat transfer fluid penetrates

  in compartment 5 via tubing 8, successive pass-

  in compartments 10, 6 and 11 via

  tubes and spring through the tubing 13.

  When the fluid circulates in the second circuit and not in the first circuit (for example when starting the engine cold), the tubes connecting the compartments 4 and 9, in which the fluid does not circulate, are at ambient temperature (by example 20 C), while those connecting compartments 5 and 10 are approximately at the temperature of the fluid at its entry into the exchanger (for example 90 ° C.), that is to say a temperature difference of 70 C between the two sub - sets. The tubes being generally rigidly connected to the fluid boxes, for example by brazing to the manifolds, the difference in expansion resulting from this difference in temperature between two neighboring sub-assemblies

  causes excessive mechanical stress.

  The object of the invention is to remedy this drawback.

  The invention relates in particular to a method as defined above

  above, and provides that at least one of said compartments belonging to the second circuit is located there upstream of said

second compartment.

  Other characteristics, complementary or alternative, of the invention are set out below: - The tubes are rigidly connected to each other

of their ends.

  - The tubes are rigidly connected together by

through the collector.

  - The second compartment is the one furthest downstream in

the second circuit.

  - The heat transfer fluid of the first circuit and that of the second circuit penetrate into said multiple heat exchanger

  respectively by the first compartment and by a third

  5th compartment of the fluid box.

  - The first compartment is the only compartment of the

  fluid box belonging to the first circuit.

  The invention also relates to a multiple heat exchanger suitable for implementing the method such as

  defined above, comprising a bundle of circulation tubes

  tion of heat transfer fluid comprising at least one row of substantially parallel tubes, each tube passing through a perforated wall or manifold of at least one fluid box, the latter being divided by partitions, at least in the vicinity of the manifold, into several compartments, each communicates with a subset of the tubes of the row, a first of said compartments belonging to a first heat transfer fluid circuit and at least a second

  compartment, adjacent to the first, and a third compartment

  ment belonging to a second heat transfer fluid circuit in which they are arranged in series by means of circulation tubes and, where appropriate, intermediate compartments and / or another fluid box, characterized in that the first and third compartments are interconnected by an internal channel of the fluid box to be supplied by the same fluid inlet pipe, said

  channel being bounded by a wall adjacent to the second compar-

  timent and where appropriate to said intermediate compartments

  res. In the case where the outer walls of the fluid box, said partitions and said channel wall are defined by a molded part, one of said outer walls advantageously has, in the extension of the channel, an opening

  mold release which can be closed by a plug.

  The characteristics and advantages of the invention will be

  described in more detail in the description below, in

  referring to the attached drawings, in which: - Figure 1 is a schematic view of a known multiple heat exchanger, and has already been described above; - Figure 2 is a view similar to Figure 1, relating to a heat exchanger according to the invention; and - Figure 3 is a partial sectional view of another

  heat exchanger according to the invention.

  In FIG. 2, the same reference numbers are used as in FIG. 1 to designate identical or analogous elements. The portion of the heat exchanger used by the cooling circuit of the heat engine, comprising the inlet pipe 7 and the compartment 4 of the box

  fluid 1, a first subset of the tubes 3, the compartment

  ment 9 and the outlet pipe 12 of the fluid box 2, is unchanged with respect to FIG. 1. On the other hand, the portion used by the charge air cooling circuit, whose internal configuration is the same as 'in Figure 1, is oriented differently. Compartment 6 is located between compartments 4 and 5, and compartment 11 between compartments 9 and 10. As a result, the circulation tubes of the second circuit closest to the circulation tubes of the first circuit are those connecting compartments 6 and 11. The circulating fluid

  in these tubes, already cooled by two passes (from the compartment

  5 to compartment 10 and from the latter to compartment 6), is for example at a temperature of 45 ° C., reducing to

  'C the temperature difference with the tubes of the first sub-

  together when there is no fluid circulating, and thus considerably limiting the stresses produced by the

differential expansion.

  When the two circuits are supplied, and using the examples given above, the fluid circulating between compartments 4 and 9 is at 90 ° C and that circulating between compartments 6 and 11 is at 45 ', a difference in temperature 45 ° C, while in the arrangement of Figure 1 the fluid flowing in the two sub-assemblies of neighboring tubes, between compartments 4 and 9 and between the

  compartments 5 and 10, was at the same temperature of 90'C.

  The arrangement according to the invention therefore creates in this case a differential expansion which did not exist in the state of the art. However, the important result is that the maximum temperature difference, in all of the operating phases, between neighboring tubes belonging to the two circuits is significantly lower (45 ° C.) in the configuration according to the invention than in the configuration

known (70 C).

  The same reference numbers are again used in FIG. 3 as in FIG. 2. The fluid box 2 and the tube bundle 3 of FIG. 3 are identical to the corresponding elements of FIG. 2. The fluid box 1 of FIG. 3 differs from that of FIG. 2 in that the compartments 4 and 5, which are separated from one another by the compartment 6 in contact with the perforated plate or collector 14 traversed by the tubes 3, are connected together by a channel 15 remote from the manifold, this channel being separated from the compartment 6 by a wall 16 extending in the longitudinal direction of the fluid box. The channel 15 makes it possible to supply the compartments 4 and 5 from the same inlet pipe 7, the pipe 8 being removed, which

  simplifies the entire cooling circuit.

  The fluid box 1 is formed by assembling the manifold 14 and a molded plastic part defining the outer walls, the tubing 7, the partitions between the compartments and the wall 16. When molding this part, a nucleus is present in channel 15. During demolding, this

  nucleus is extracted by a movement in the longitu-

  dinal of the fluid box, leaving an opening 17 in an end wall 18 of the fluid box. This opening must then be closed by means of a plug 19,

for example by welding.

  In the embodiments described, the inlet pipes of the two circuits are on the first fluid box and the outlet pipes of the two circuits are on the second fluid box. Alternatively, the two inlet pipes, and / or the two outlet pipes, can be placed on the two fluid boxes respectively. Likewise, the inlet and outlet pipes of the same circuit can be on the same fluid box. The second fluid box can be totally or partially removed, the tubes

  corresponding straight lines being replaced two by two, in a known manner, by U-shaped or hairpin tubes. The heat exchanger according to the invention can be used, in addition to the first and second circuits, for other circuits.

Claims (8)

Claims   1. Cooling process, in particular of the heat engine   that of a motor vehicle, using at least a first circuit and a second heat transfer fluid circuit which have in common a multiple heat exchanger comprising a bundle (3) of heat transfer fluid circulation tubes   comprising at least one row of substantially parallel tubes   the, each tube passing through a perforated wall or manifold (14) of at least one fluid box (1), the latter being   divided by partitions, at least in the vicinity of the collection   in several compartments (4,5,6) each of which communicates   that with a subset of the tubes of the row, a first (4) of said compartments belonging to the first circuit and at least two other compartments (5,6), among which a second compartment (6) adjacent to the first, belonging to the second circuit in which they are arranged in series by means of circulation tubes, method comprising phases during which the heat transfer fluid circulates simultaneously in the first and second circuits and other phases during which the heat transfer fluid circulates in the second circuit and not in the first circuit, characterized in that at least one (5) of said compartments belonging   the second circuit is located there upstream of said second compartment ment (6).   2. Method according to claim 1, characterized in that the tubes are rigidly connected to each other, to each of their ends.   3. Method according to claim 2, characterized in that   the tubes are rigidly connected to each other through the collector medial (14).   4. Method according to one of the preceding claims,   characterized in that the second compartment (6) is that   located furthest downstream in the second circuit.   5. Method according to one of the preceding claims,   characterized in that the heat transfer fluid of the first circuit and that of the second circuit enter said multiple heat exchanger respectively through the first compartment (4) and through a third compartment (5) of the fluid box (1).   6. Method according to claim 5, characterized in that the first compartment (4) is the only compartment of the   fluid box (1) belonging to the first circuit.   7. Multiple heat exchanger suitable for setting up   work of the method according to one of claims 5 and 6,   comprising a bundle (3) of fluid circulation tubes   coolant comprising at least one row of sensitive tubes   ment parallel, each tube passing through a perforated wall or manifold (14) of at least one fluid box (1), this   the latter being divided by partitions, at least in the vicinity   swimming of the collector, in several compartments (4,5,6) each of which communicates with a subset of the tubes of the row, a first (4) of said compartments belonging to a first heat transfer fluid circuit and at least a second compartment ( 6), adjacent to the first, and a third compartment (5) belonging to a second heat transfer fluid circuit in which they are arranged in series by means of circulation tubes and, where appropriate, intermediate compartments and / or a other fluid box   (2), characterized in that the first and third compar-   timents (4,5) are interconnected by an internal channel (15) of the fluid box to be supplied by the same fluid inlet pipe (7), said channel being limited by a wall (16) adjacent to the second compartment (6) and the case   appropriate to said intermediate compartments.   8. Heat exchanger according to claim 7, character-   laughed in that the outer walls of the fluid box, said partitions and said wall (16) of the channel (15) are defined by a molded part, one (18) of said outer walls having, in the extension of the channel, a release opening (17) which can be closed by a plug (19).