FR2568000A1 - FINED EXCHANGER TUBE - Google Patents

Abstract

FINNED EXCHANGER TUBE, CONSTITUTED BY A TUBE 1 AROUND WHICH IS WOUND, ON THE EDGE, A METAL BAND 2 WELDED TO ITS BASE TO THE TUBE, CHARACTERIZED IN THAT THE SAID METAL BAND IS MADE BY THE ASSEMBLY, BY WELDING END TO END , OF TWO STRIPES 4, 6 OF DIFFERENT METALS, THE ONE 4 WELDED ON THE TUBE HAVING A COEFFICIENT OF EXPANSION VERY NEAR THAT OF THE TUBE AND THAT 6, LOCATED FAREST ON THE OUTSIDE, HAVING A COEFFICIENT OF CONDUCTIBIL MORE THAN THE CONDUCTIBIL OF THE TUBE.

Description

The present invention relates to a tube with fins

  exchanger having cooling fins for extending the heat exchange surface. The fins consist of a strip of coiled strip

  on a spiral edge around the tube and welded all along.

  The strip of strip is generally notched at regular intervals on its outer edge so as to form notches in order to allow its winding on the tube which also promotes the

circulation of the external fluid.

  When the tube and the strip are made of identical metal, we are in a favorable situation from the point of view of thermal stresses, however, sometimes we have to use tubes made of special steels, such as stainless steel. , when the fluid to be conveyed through the tube is corrosive or the severe operating conditions. If then a strip also made of stainless steel is used to make the fins, the heat efficiency of the exchanger is not optimum and

  it is necessary to produce large exchangers.

  We can then, in this case, use a strip of another metal better conductor of heat, for example nickel, but then we have constraints due to differential expansions between tube and fin, and such a solution is not applicable to high temperatures, for example for an exchanger in which a

fluid at 550 C air-cooled.

  The object of the present invention is therefore to produce a sample tube.

  finned applicator applicable to the case of a tube made of a metal which is a relatively poor conductor of heat and which nevertheless can operate with a fluid at very high temperature without excessive stresses due to differential expansions and making it possible to /

  make a heat exchanger as small as possible.

  The present invention therefore relates to a finned exchanger tube, consisting of a tube around which is wound, on edge, a metal strip welded at its base to the tube, characterized in that said metal strip is produced by assembly , by butt welding, of two strips of different metals, the one welded to the tube having a -2 coefficient of expansion very close to that of the tube and the one located outermost, having a coefficient of thermal conductivity

higher than that of the tube.

  Advantageously, said metal strip comprises notches extending from the outside until slightly beyond the weld between the

  two strips constituting said strip.

  The invention will be clearly understood in the light of the description of a

  exemplary embodiment of the invention made below, with reference to the appended drawing in which: FIG. 1 shows in perspective a portion of exchanger tube

according to the invention.

  Figure 2 shows a top view of the tape winding

metal around a tube.

  FIG. 1 therefore represents a portion of a tube 1 of a heat exchanger comprising a fin 2 wound in a helix around the tube. The tube 1 is for example a stainless steel tube conveying for example liquid sodium at 550 C. According to the invention, the fin 2 is made in two parts. It consists of a heel 3 made from a stainless steel strip 4 (fig.2) and a crenellated outer part 5 made from a strip 6 (fig.2) of another metal , having better thermal conductivity than the stainless steel of the tube 1 and the heel 3, for example made of nickel. The fin 2 is thus wound in a helix around the tube 1 and welded by its heel against the tube. We proceed as follows; we start by welding side by side the two strips: 4 in stainless steel and 6 in nickel. Then, cuts 7 are made so as to make notches. The cutouts 7 reach and even slightly exceed the weld bead 8. The strip thus formed is then wound and welded on the

tube 1.

  The strip 4 constituting the heel 3 of the fin 2 is made, in the example cited, of the same metal as that of the tube 1. It is optionally possible to use a different metal provided that its

  coefficient of expansion is very close to that of the metal of the tube.

  It is well understood that the arrangement according to the invention makes it possible to avoid the constraints due to differential expansions, while improving the heat exchange coefficients thanks to the part 5 of

  the metal fin 2 having better thermal conductivity.

  The strips 4 and 6 are not necessarily the same thick-

  sister. Furthermore, in the case of a tube 1 of large diameter or else if the width of the external strip 6 is small, it is possible to omit the

cuts 7.

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Claims (3)

  1 / Finned exchanger tube, consisting of a tube (1) around which is wound, on edge, a metal strip (2) welded at its base to the tube, characterized in that said metal strip is produced by assembly , by butt welding, of two strips (4, 6) of different metals, that (4) welded on the tube having a coefficient of expansion very close to that of the tube and that (6) located the outermost having a higher coefficient of thermal conductivity than that of the tube.   2 / exchanger tube according to claim 1, characterized in that said metal strip comprises notches (7) extending from the outside until slightly beyond the weld (8) between the two   strips constituting said strip.   3 / exchanger tube according to one of claims 1 or 2, characterized   in that said strip welded to the tube is of the same metal as the tube.