HEAT EXCHANGER WITH IMPROVED FINS

Abstract

The invention relates to a heat exchanger (1) comprising at least one tube (2) for heat transfer fluid to flow through, connected to at least one heat dissipation fin (4). The fin (4) is made of expanded metal sheet.

Description

The present invention relates to a heat exchanger, and more particularly to a mechanical heat exchanger.

A heat exchanger generally comprises tubes, through which a heat transfer fluid is intended to flow, and heat exchange elements connected to these tubes.

A distinction is usually made between brazed heat exchangers and mechanical heat exchangers depending on the method for manufacturing them.

In a mechanical heat exchanger, the heat exchange elements, referred to as “fins” in this case, are connected to the tubes in the following way. First of all, through-holes for the tubes to pass through are made in the fins. These through-holes are generally each delimited by a raised edge forming a neck. Next, the fins are disposed substantially parallel to one another and each tube is inserted into a row of aligned holes in the fins. Finally, a radial expansion of the tubes is brought about by passing an expansion tool through the inside of these tubes so as to mechanically join the tubes and the fins by crimping, the necks delimiting the through-holes for the tubes then forming collars clamped around the tubes.

The fins of this type of tube are generally made from smooth metal sheets.

The aim of the invention is to propose a heat exchanger in which the heat exchange performance is improved while the mass thereof is limited.

To this end, the subject of the invention is a heat exchanger comprising at least one tube for heat transfer fluid to flow through, connected to at least one heat dissipation fin, characterized in that the fin is made of expanded metal sheet.

The fact that the fin is made of expanded metal sheet makes it possible to increase the heat exchange between the air and the fin while limiting the mass of the heat exchanger, since the heat exchange surface area of the fin is increased compared with a smooth metal sheet, without otherwise adding material thereto.

In one particular embodiment, corresponding to a mechanical heat exchanger, the tube is connected to the fin by clamping the tube in a collar formed in the fin.

Preferably, in order to further increase the heat exchange between the air and the fin, with the heat exchanger comprising a row of substantially parallel tubes, the fin comprises at least one row of deflectors forming louvers, said row being formed in the fin and interposed between two tubes of the row of tubes.

In one particular embodiment of the invention, the expanded metal sheet comprises meshes that are each in the overall shape of a rhombus.

Preferably, in order to lighten the heat exchanger, the expanded metal of the sheet comprises aluminum.

The invention also relates to a method for manufacturing a fin of a heat exchanger according to the invention, the fin being formed from a metal sheet, characterized in that

• • a) the metal sheet is compressed between two complementary rows of aligned teeth borne respectively by two jaws of a press;
  • b) the two rows of teeth are moved by half a pitch, a pitch corresponding to the distance between the consecutive apices of two teeth in the same row;
  • c) the metal sheet is moved transversely to the rows of teeth by a distance corresponding to the width of one tooth;
  • d) step a) is repeated;
  • e) the two rows of teeth are moved by half a pitch in the opposite sense to that in step b);
  • f) steps a) to e) are repeated;
  • g) through-holes for a tube to pass through are formed.

In one particular embodiment, the method includes the additional step of forming louvers between said through-holes.

The invention will be understood better from reading the following description, which is given solely by way of example and with reference to the drawings, in which:

FIG. 1 is a partial perspective view of a fin of a heat exchanger according to one particular embodiment of the invention;

FIGS. 2 to 7 are schematic perspective views of a press for manufacturing a fin during different steps in a method for manufacturing the fin according to one particular embodiment of the invention.

FIG. 8 is a schematic view of a heat exchanger according to the invention.

FIG. 1 shows a fin of a mechanical heat exchanger 1 intended to equip a motor vehicle.

The heat exchanger comprises a row of substantially parallel tubes 2 through which a conventional heat transfer fluid is intended to flow, and superposed heat dissipation fins 4 that are connected to these tubes 2.

The tubes 2 are connected to the fins 4 by clamping the tubes in collars 6 formed in the fins 4. To this end, the fins 4 are provided with through-holes 8 for the tubes to pass through. These through-holes 8 are each delimited by an edge forming a collar 6 and having two long edge portions connected by two short semicircular edge portions. The through-holes each have an oblong overall shape with long portions which are slightly concave in their middle.

In the example described, the tubes 2 each have a shape corresponding to that described by the through-holes. The tubes 2 are arranged substantially parallel to one another, so as to form a single row.

The fins 4 have a substantially flat rectangular overall shape and are arranged in the heat exchanger 1 in a manner substantially parallel to one another and perpendicular to the longitudinal directions of the tubes 2.

The heat exchanger 1 allows an air flow to pass from upstream to downstream, the fins 4 being intended to extend through this flow. Arrows F indicate the direction of travel of the flow in FIG. 1.

In order to increase the heat exchange between the flow F and the fins 4, the heat exchanger 1 also comprises rows 10 of deflectors 12 forming louvers, which are formed in each fin 4 and are each interposed between two tubes 2.

The fin 4 is made of expanded metal sheet, and consequently so are the deflectors 10. Preferably, the metal of the sheet comprises aluminum, for example an alloy comprising substantially aluminum.

More particularly, the expanded metal sheet comprises meshes 12 that are each in the shape of a rhombus.

A method for manufacturing a fin 4 of a heat exchanger 1 according to the invention will now be described, the steps of said method being illustrated in FIGS. 2 to 7.

Since the fin 4 is formed from a metal sheet 16, this metal sheet 16 is firstly compressed between two complementary rows 18 of aligned teeth 20 that are borne respectively by two jaws 22 of a press 24.

This is realized for example by lowering the upper jaw 22 in the direction and sense indicated by the arrow C in FIG. 2, the compression being illustrated in FIG. 3.

Next, the two rows 18 of teeth are moved by half a pitch, a pitch corresponding to the distance p between the consecutive apices of two teeth 20 in the same row 18. This movement is indicated by the arrow P₁ in FIG. 4.

Then, the metal sheet 16 is moved transversely to the rows 18 of teeth by a distance d corresponding to the width of one tooth 20. This movement is indicated by the arrow D shown in FIG. 5.

Once the step of compression between the rows 18 of teeth 20 has been repeated, as shown in FIGS. 5 and 6, the two rows 18 of teeth 20 are moved by half a pitch in the opposite sense to the arrow P₁, that is to say in the sense of the arrow P₂, shown in FIG. 7.

In order to obtain the expanded metal fin 4 as shown in FIG. 1, the above steps are repeated until the entire surface of the sheet 16 has been compressed, and then the holes and the louvers are realized.

The invention is not limited to the embodiment presented, and further embodiments will be dearly apparent to a person skilled in the art. For example, according to an embodiment that is not shown, the tubes have a circular cross section and the corresponding through-holes are circular.

Claims

1. A heat exchanger comprising:

at least one tube for heat transfer fluid to flow through, connected to at least one heat dissipation fin,

wherein the fin is made of expanded metal sheet.

2. The heat exchanger as claimed in claim 1, the tube being connected to the fin by clamping the tube in a collar formed in the fin.

3. The heat exchanger as claimed in claim 1, further comprising a row of substantially parallel tubes, wherein the fin comprises at least one row of deflectors forming louvers, said row being formed in the fin and interposed between two tubes of the row of tubes.

4. The heat exchanger as claimed in claim 1, wherein the expanded metal sheet comprises meshes that are each in the overall shape of a rhombus.

5. The heat exchanger as claimed in claim 1, wherein the expanded metal sheet comprises aluminum.

6. A method for manufacturing a fin of a heat exchanger as claimed in claim 1, the fin being formed from a metal sheet, the method comprising:

a) compressing the metal sheet between two complementary rows of aligned teeth borne respectively by two jaws of a press;

b) moving the two rows of teeth by half a pitch, the pitch corresponding to the distance between the consecutive apices of two teeth in the same row;

c) moving the metal sheet transversely to the rows of teeth by a distance corresponding to the width of one tooth;

d) re-compressing the metal sheet between the two complementary rows of aligned teeth

e) moving the two rows of teeth are moved by half a pitch in the opposite sense to that in step b);

f) repeating steps a) to e); and

g) forming through-holes for a tube to pass through.

7. The method as claimed in claim 6, further comprising the additional step of forming louvers between said through-holes.