FR2811416A1 - TWO-CHANNEL FLUID TYPE HEAT EXCHANGER - Google Patents

Abstract

The invention relates to a heat exchanger. This exchanger is of the type comprising at least one flow path for a cooling fluid, such as water, refrigerant or even air, and at least one second flow path for a fluid such as as air, at least the second path comprising a plurality of flow channels. The exchanger is characterized in that it comprises means for evacuating by suction the water which had condensed on the walls of the air flow channels. The invention can be used in heat exchangers.

Description

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  The invention relates to a heat exchanger of the type with two fluid flow paths, in particular crossed or parallel, a first channel comprising a plurality of flow channels for a first cooling fluid, such as water, and the second channel comprising a plurality of channels for the flow of a gaseous fluid such as air. In heat exchangers of this type, which are known, the air which flows through the channels of the second channel is cooled by water to a temperature close to that of this water. Consequently, part of the moisture contained in the air flow condenses on the walls of the channels. For thermal reasons, the channels can be narrow in at least one of their dimensions and capillary forces can therefore be exerted on the condensate which then accumulates on the walls of the channels. The first consequence is that large amounts of condensate can be entrained by the air flow during an increase in air flow. This phenomenon called "wave" is unacceptable for certain applications. Two other consequences of this accumulation are an increase in the pressure drop of the exchanger on this air circuit and a decrease in the heat exchanges of

  by the thickness of water retained on the fins.

  The invention aims to provide a heat exchanger which overcomes

  The drawback which has just been stated of known heat exchangers.

  To achieve this goal, the heat exchanger according to the invention is characterized in that it comprises means for evacuation by suction of water

  condensed at the outputs of the air flow channels.

  According to a characteristic of the invention, the water accumulated at the ends of the channels is sucked through recesses which communicate with a

  space in which a depression reigns.

  The invention will be better understood, and other aims, characteristics, details

  and advantages thereof will appear more clearly in the description

  explanatory which will follow made with reference to the appended schematic drawings given solely by way of example illustrating an embodiment of the invention and in which:

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  - Figure 1 is a schematic perspective view of a heat exchanger according to the present invention; - Figures 2 and 3 are perspective views, broken away, of two other embodiments of the heat exchanger, according to Figure 1, and - Figures 4a, b, c, d are views in the direction of arrow IV of FIG. 1 and show four possibilities of configuration of suction recesses

  of water from the heat exchanger according to the invention.

  As can be seen from the figures, a heat exchanger according to the present invention comprises, superimposed, in an alternating manner and so as to intersect, a path 2 for the flow of a cooling fluid, such as water and a path 3 for the flow of a gaseous fluid such as air. A track 2 or 3 is delimited between two walls 5 in the form of plates, parallel and rectangular. This path is closed by side wall elements 7 with two opposite sides and open to the other two parallel sides. The space thus delimited is subdivided into a

  i5 plurality of flow channels 8 by parallel separation fins 9.

  In the example shown in the figures, the fins are part of an interlayer consisting of a sheet configured so as to have a zigzag profile. The

  the shape of the interlayer in the direction of flow can be arbitrary.

  As can be seen in FIG. 1, in a heat exchanger according to the invention, the plate-shaped walls 5 extend beyond the ends 11 of the air flow channels, that is to say say the ends of the interlayer delimiting these channels, by a predetermined distance. This part of the plates is therefore free of fins. FIG. 1 also shows that in the water flow path 2, the space 15 between two spaces 14 is also free of fins 9. This space 15 delimited laterally by an end wall 7, of a part, and the outer fin 9 formed by the end branch of the interlayer or of another end wall is connected in a non-

  shown in a space not shown in which there is a depression.

  An essential characteristic of the invention resides in the fact that the walls 5 have, in their exposed part 14, near the ends 11 of the air flow channels, through recesses 17 which then open into a space (5) in which reigns a weak depression. The purpose of these recesses 17 is to allow the suction of the water which has condensed on the walls of the fins and which has come under the effect of the flow of water in the channels at the ends 11. This water is therefore evacuated by suction through the recesses 17. These recesses 17 prevent the accumulation of condensate at the ends 11 and thus the release of this water in the form of "spontaneous waves". They are provided at a distance

  relatively small appropriate ends.

  FIGS. 2 and 3 show two particularly advantageous configurations of the ends of the fins 9. The objective of these configurations is to modify the geometry of the exchanger and to create pressure gradients in order to

  overcome capillary forces, which tend to retain water in the fins.

  In the version shown in Figure 2, the ends are curved or curved so that the middle part of each fin is recessed and the condensate is pushed by the air flowing in the channel to the part of plate i5 released 14 and thus in the direction of the suction recesses 17. In the version according to FIG. 3, each fin end 11 is cut at the top and at the bottom at 19 along a line in the form of an L so that the middle part shows the

  U-shaped, the base 20 of which projects in the direction of the air flow.

  The suction recesses 17 are made in the plate parts 14 in the L-shaped cutting area. This second variant amounts to placing the recesses 17 at the end of the air channels. It is however also possible to envisage placing the recesses 17 further upstream in the air channels on a line or distributed so as to optimize the suction which is then done either in a space separate from the channels of

  cooling, either directly in the coolant channels.

  Figure 1 shows, by way of example at 27, recesses opening into a channel of the cooling fluid. Of course, there could be several lines of recesses opening into cooling channels,

  different, offset in the air flow direction.

  Figures 4 to 4d illustrate several embodiments of the suction recesses 17 to 27. In Figure 4a, the recesses 17 are formed by circular holes 22. In Figure 4b, each recess has the shape of a slot substantially rectangular 23. Three slots are aligned over the width of the suction part 14. In the version shown in FIG. 4c, the recess 17 has the shape of an S-shaped slot 24. Over the width of the suction part 14 three slots 24 are aligned and arranged so that they overlap at their ends. Thus we obtain a suction effect over the entire width without interruption while avoiding weakening

  mechanical resistance of the wall.

  The embodiment of the recesses according to FIG. 4d has the particularity that two rows of parallel holes are made in the suction part 14. The two series of holes are offset in the direction of the air flow. The holes in the two rows are arranged so that a hole in one row is between two holes in the other row. These holes can

  of course have any appropriate and different shape in the two rows.

  Thus, in FIG. 4d, a row has circular holes 25 and holes

triangular 26.

  In general, the end shapes of the fins and the shapes of the recesses, which are shown in the figures, are given only by way of examples and can be modified provided that water is sucked in. on the wall of channels along these channels and / or reaching the ends of the

  fins and which would accumulate there without this evacuation through the recesses.

  Of course, the coolant could be of any other nature

  suitable and be refrigerant, any liquid other than water or even be air.

Claims (14)

  1. Heat exchanger of the type comprising at least one flow path for a cooling fluid, such as water, refrigerant or even air, and at least a second flow path for a fluid such as air, at least the second channel comprising a plurality of flow channels, characterized in that it comprises means for evacuation by suction of water   which had condensed on the walls of the air flow channels.   2. Heat exchanger according to claim 1, characterized in that the evacuation means comprise suction orifices (17) which communicate   with the coolant flow channels.   3. Heat exchanger according to claim 1, characterized in that the suction means are provided at the outlets (11) of the flow channels of gaseous fluid (8).   4. Heat exchanger according to claim 3, characterized in that the means for discharging the water comprise suction orifices (17) provided in the   level of the outlets (11) of the flow channels (8).   5. Heat exchanger according to claim 4, characterized in that the suction orifices (17) communicate with a space (15) in which there is a depression.   6. Heat exchanger according to one of claims 1 to 5, in which   the air flow channels (8) are juxtaposed and formed between two substantially parallel plates (5), characterized in that said plates (5) extend at (14) beyond the ends (11) of the channels air flow (8) and in that the suction orifices (17) are formed by through recesses   communicating with said vacuum space (15).   7. Heat exchanger according to claim 6, characterized in that the aforementioned space (15) is delimited in the flow path (2) of the cooling water and in that the suction recesses (17) lead into this space (15).   8. Heat exchanger according to one of claims 6 or 7, characterized   in that the ends (11) of the walls (9) delimiting the flow channels 6 2811416   air (8) between the two plates (5) have a shape ensuring a   condensate flow to the suction ports (17).   9. Heat exchanger according to one of claims 6 to 8, characterized   in that the ends (11) of the delimiting walls (9) of the flow channels (8) between two plates (5) have a curved shape so   the end is set back in its middle part.   10. Heat exchanger according to one of claims 6 to 8, characterized   in that the end (11) of a wall (9) delimiting the air flow channels between the two plates (5) are configured so that the middle part io projects in the direction of air flow in relation to the parts adjacent to the plates (5) and in that the suction openings (17) are provided   substantially below the protruding parts.   11. Heat exchanger according to one of claims 6 to 10,   characterized in that the suction recesses (17) are formed by at least one series of holes (22) distributed over the width of the projecting part (14) of the plates (5).   12. Heat exchanger according to one of claims 6 to 10,   characterized in that the suction recesses (17) are formed by at least   a row of slots (23) aligned with the width of the part (14) of the plates (5).   13. Heat exchanger according to claim 12, characterized in that a slot (23) has the shape of an S (24) and in that the slots are   aligned so that they overlap at their ends.   14. Heat exchanger according to claim 11, characterized in that it comprises at least two rows of holes (25, 26), if necessary of different shape, a hole of a row lying in the middle of a hole from another row.