EP0546969B1 - Cylindrical enclosure of large diameter for cooling components - Google Patents

Description

The subject of the present invention is a large-diameter cylindrical enclosure intended to receive members which have to be cooled by an external fluid such as in particular apparatuses for power electronics of a high speed train.

It will find its application in all areas where it is necessary to use an enclosure that must contain devices, possibly precision, which must be cooled by an external heat transfer fluid.

In many industrial sectors such as the chemical or petrochemical industry, the waste treatment industry, the nuclear or conventional energy industry, as well as in the packaging industry. air and rail transport, enclosures are used which must be cooled by an external fluid. These enclosures are intended in particular to contain different types of devices or apparatus necessary for the control, or command of industrial installations as well as that of the power cars.

To allow this heat exchange, for example, use is made of fins regularly arranged on the periphery of the external surface of a tube, according to a distribution and a distribution which vary according to the nature of the use.

In addition, these fins must have the largest possible heat exchange surface in order to allow a satisfactory heat exchange efficiency.

For this, we currently know different types of fins whose shape, nature and constitution also depend on their use and the desired result.

These fins are placed on tubes of small diameters which considerably limits their possibilities of use.

Thus, such tubes can only be used to contain devices of small dimensions or to ensure the circulation of fluids.

A first type of fins used is constituted by straight fins.

These fins are produced by a metal ribbon which has been previously wound on a suitable machine, a ribbon which is wound on the body of the small diameter tube by exerting significant pressure to ensure their maintenance while forming a seat by knurling each side of the fin. Such methods are limited to very small tubes, the diameter of which can only go up to a few centimeters.

One can also use to produce such fins, a device which comprises two non-cutting discs arranged perpendicular to the body of the tube to be covered. The first disc provides a groove on the smooth face of the tube while the second disc guides the metal strip inside the said groove by exerting sufficient pressure on only one side of the fin in order to maintain it.

In an alternative embodiment, it is also possible to dig a groove which is no longer straight but helical on the external face of the enclosure and push the metal on either side inside this groove. To do this, the pre-wound metal tape is introduced into this groove by tightening it strongly. The edges formed on either side are crushed and pushed back on each side of the fin.

Whatever the embodiment, these fins can only be placed on tubes of small diameters. In addition, they have the disadvantage of not being sufficiently maintained in the groove so that in certain types of use, this considerably reduces the efficiency of the heat exchange and therefore the calorific efficiency of the device.

This poor mechanical strength of the connection can also have the consequence of releasing the smooth surface of the tube so that this smooth surface is then subject to corrosion.

This corrosion being all the more accentuated when such tubes are used in humid atmospheres or when the heat transfer fluid is itself corrosive.

To overcome these drawbacks, it has been thought to produce fins which have a body, in cross section of L or double L.

By document US-A-3,388,449 (or FR-A-2,060,217), a cylindrical enclosure is already known, having to be cooled by an external heat transfer fluid, and which has a smooth external surface, at least partially covered with fins regularly distributed over the smooth external surface in a helical arrangement with a fixed pitch, each fin having a body having, in cross section, a substantially L or double L configuration, comprising a foot and a base applied against the smooth external surface, the fins being wound under tension on the smooth external surface by partially overlapping so that their base is at least partially covered by a foot and / or a base of the fin adjacent to the corresponding side.

Furthermore, from document US-A-4,514,900, a tube with helical fins of L-section is known, the entire external surface of the base of each fin is counter-knurled to anchor this base in a continuous knurling on the surface outside of the tube.

To do this, we first of all knurl the external face of the small-diameter tube, then roll up the metal tape which is formed into an L and which is knurled by exerting pressure on the foot of the L of so as to nest each L-shaped foot in each other.

Thanks to this counter-knurling of the L-shaped or double L-shaped fin relative to the external surface of the tube, tubes of small diameter are produced, the fins of which are perfectly maintained on their surface.

This ensures good transmission of calories with minimum pressure drop.

In addition, with such types of fins, better protection of the external surface of the tube against corrosion is obtained, as well as the possibility of use at higher temperatures.

However, such tubes must necessarily have an external surface which can be knurled. However, in many types of application, it is impossible to knurle the external surface of the tube since it must contain very fragile or even precise devices or members which are arranged in a determined configuration which does not allow any knurling of the external wall. of the tube.

This is particularly the case of enclosures which must contain power electronics for high speed trains.

With such enclosures, there is therefore a problem which is that of the fitting of fins which must have perfect mechanical strength despite the smooth surface of the enclosure.

Furthermore, it is also necessary that such enclosures make it possible to obtain excellent heat exchange efficiency results whatever the conditions of use.

This problem is further increased since all these enclosures are generally very large diameters. They must also imperatively be protected against any type of chemical or mechanical attack.

In this case, the solution of the straight fins stacked or even welded is not satisfactory.

Furthermore, when such fins are used to make these enclosures with large diameters, it is necessary to have recourse to methods which generate a significant loss of material, which considerably increases their cost.

It should also be noted that the tightness of these enclosures must be total vis-à-vis the internal fluid as well as vis-à-vis the external atmosphere.

Finally, these enclosures are subjected to mechanical stresses which can be significant and in particular to vibrations which can generate separation of the fins from the tube.

The present invention aims to remedy the drawbacks of the devices currently known by providing a large diameter enclosure whose external surface is smooth which has excellent thermal efficiency, good resistance against corrosion as well as good mechanical resistance of the fins therebetween.

Furthermore, a surprising advantage of such enclosures lies in the fact that the fins have a distribution of localized radial undulations, which promotes the flow of the fluid in particular by vortex phenomenon, this flow of the fluid causing an increase in the thermal efficiency.

To this end, according to the invention, the cylindrical enclosure to be cooled by an external heat transfer fluid, and which comprises, as known by US-A-3,388,449, a smooth external surface at least partially covered with fins regularly distributed over said smooth outer surface in a helical arrangement with a defined pitch, each fin having a body having, in cross section, a substantially L-shaped configuration, comprising a foot and a base applied against the smooth outer surface, the fins being wound under tension on said surface external smooth by partially overlapping so that their base is partially covered by the foot of the fin adjacent to the corresponding side, is characterized in that it has an axial dimension or height (H) and a diameter (D) such that the H / D ratio is between approximately 1.14 and approximately 5.33, and in that each fin has a knurling which extends over the surface of the part of the base which is covered by the foot of the adjacent fin.

Alternatively, when each fin has a body having, in cross section, a substantially double L configuration, comprising a first leg and a first base applied against the smooth external surface, the fins being wound under tension on said smooth external surface by partially overlapping so that their first base is at least partially covered by a second leg and a second base of the fin adjacent to the corresponding side, the enclosure according to the invention is characterized in that it has an axial dimension or height (H) and a diameter (D) such that the H / D ratio is between approximately 1.14 and approximately 5.33, and in that each fin has, on part of its first base, a first knurling which is covered by the second base of the fin adjacent to the corresponding side, and in that said second base has a second knurling on the surface of its part which covers the knurling presented by the first base covered with the adjacent fin on the other side.

• on réalise une enceinte cylindrique dont au moins une partie de la surface externe est lisse,
• on déroule en continu un ruban métallique selon une vitesse déterminée ; puis,
• on applique au ruban une traction en réalisant un corps d'une ailette de section transversale en forme sensiblement de L ou de double L tout en exerçant en même temps une rétention du défilement dudit ruban,
• on dispose des ailettes sous tension selon une répartition hélicoïdale à pas (A) déterminé sur au moins la partie lisse de la surface externe de l'enceinte cylindrique, en synchronisant la vitesse de mise en place des ailettes avec la vitesse de défilement du ruban,
  ce procédé étant caractérisé en ce qu'on réalise ladite enceinte cylindrique avec une dimension axiale ou hauteur (H) et un diamètre (D) tels que le rapport H/D est compris entre environ 1,14 et environ 5,33, et
• on réalise au moins un moletage sur une partie du ruban qui est destinée à former une partie d'ailette recouverte par l'ailette suivante formée sur l'enceinte.

The subject of the invention is also a method for producing an enclosure as presented above, and according to which:

• a cylindrical enclosure is produced, at least part of the external surface of which is smooth,
• a metallic strip is continuously unwound at a determined speed; then,
• a tension is applied to the ribbon by producing a body of a fin of cross section in the form of a substantially L or double L while at the same time retaining the movement of the said ribbon,
• the fins are placed under tension according to a helical distribution with a pitch (A) determined over at least the smooth part of the external surface of the cylindrical enclosure, by synchronizing the speed of fitting of the fins with the speed of movement of the ribbon,
  this process being characterized in that said cylindrical enclosure is produced with an axial dimension or height (H) and a diameter (D) such that the H / D ratio is between approximately 1.14 and approximately 5.33, and
• at least one knurling is carried out on a part of the strip which is intended to form a part of a fin covered by the following fin formed on the enclosure.

• des moyens pour réaliser une enceinte cylindrique dont au moins une partie de la surface externe est lisse,
• des moyens pour stocker un rouleau de ruban métallique,
• des moyens pour exercer une traction selon une vitesse déterminée sur le ruban,
• des moyens pour retenir le ruban accouplé aux moyens pour exercer une traction sur ledit ruban,
• des moyens pour maintenir l'enceinte cylindrique animée d'un mouvement de rotation, et
• des moyens pour former le ruban sous la forme d'ailettes de section transversale en forme de L ou double L, enroulées hélicoïdalement autour de ladite enceinte cylindrique,

et ce dispositif est caractérisé en ce que lesdits moyens pour réaliser l'enceinte permettent de former cette dernière avec une dimension axiale ou hauteur (H) et un diamètre (D) tels que le rapport H/D est compris entre environ 1,14 et environ 5,33, et en ce que le dispositif comprend également des moyens pour moleter le ruban sur au moins une partie destinée à former une partie d'ailette qui est recouverte par l'ailette suivante formée sur l'enceinte.The invention also relates to a device for implementing the above method, this device comprising:

• means for producing a cylindrical enclosure of which at least part of the external surface is smooth,
• means for storing a roll of metallic tape,
• means for exerting traction at a determined speed on the strip,
• means for retaining the ribbon coupled to the means for exerting traction on said ribbon,
• means for keeping the cylindrical enclosure animated by a rotational movement, and
• means for forming the ribbon in the form of fins of L-shaped or double L-shaped cross section, wound helically around said cylindrical enclosure,

and this device is characterized in that said means for producing the enclosure make it possible to form the latter with an axial dimension or height (H) and a diameter (D) such that the H / D ratio is between approximately 1.14 and about 5.33, and in that the device also comprises means for knurling the ribbon on at least one part intended to form a part of a fin which is covered by the next fin formed on the enclosure.

Other objects and advantages of the present invention will appear during the description which follows which is however given only for information and which is not intended to limit it.

In addition, one of the aims of this method makes it possible to install fins, at a rate high and continuous, on large diameter cylindrical enclosures whose external surface is smooth without connecting the strip and therefore without causing loss of material, which considerably reduces the cost.

Another advantage of this process is that it is particularly well suited for enclosures which have a large diameter and whose surface is smooth.

Another advantage is that it allows an adjusted fitting of the fins ensuring that they are kept under tension between them.

Another object of this process is that it allows efficient recovery of the heat exchange surface.

• la figure 1 est une vue schématique illustrant une enceinte conforme à l'invention,
• la figure 2 est une vue schématique illustrant une enceinte conforme à l'invention dont on a partiellement coupé la face avant,
• la figure 3 est une vue en coupe transversale d'une ailette en forme de simple L,
• la figure 4 est une vue schématique en coupe transversale d'une ailette en forme de double L,
• la figure 5 est une vue schématique illustrant plus particulièrement une ailette,
• la figure 6 est une vue schématique illustrant un dispositif pour la mise en oeuvre du procédé conforme à l'invention.

The invention will be better understood from the description which follows, accompanied by the accompanying drawings, among which:

• FIG. 1 is a schematic view illustrating an enclosure according to the invention,
• FIG. 2 is a schematic view illustrating an enclosure according to the invention, the front face of which has been partially cut,
• FIG. 3 is a cross-sectional view of a single L-shaped fin,
• FIG. 4 is a schematic cross-sectional view of a double L-shaped fin,
• FIG. 5 is a schematic view illustrating more particularly a fin,
• Figure 6 is a schematic view illustrating a device for the implementation of the method according to the invention.

The present invention relates to a cylindrical enclosure of large diameter intended to receive organs or devices to be cooled by an external fluid as well as a method for producing such enclosures and a device for its implementation.

It will find its application in all areas where it is necessary to house an apparatus or a device, possibly complex, fragile and of precision which must be cooled by an external heat transfer fluid.

The enclosure 1 according to the invention is more particularly adapted to receive organs of the power electronics of a high speed train as will emerge from the description which follows. Of course, this application is in no way limiting, and the size as well as the shape of the enclosure can vary to be adapted to receive other types of devices.

Thus, this enclosure can be applied in other heat transfer devices or any other cooling system.

Referring to Figure 1, we see a cylindrical enclosure 1 of large diameter and a determined height. By way of example, an enclosure intended to receive the power electronics of a TGV has a diameter D of between 150 and 350 mm and a height H of between 400 and 800 mm.

Referring to Figure 2, the enclosure 1 has an outer surface 2 perfectly smooth and an inner surface 3 can also be smooth. It is made of all types of materials. In a preferred embodiment, it is made of aluminum but it could also be made of any other material or alloys of suitable materials according to requirements such as, for example, stainless steel, copper, copper-nickel alloy, tinned copper, etc.

At each of its ends 3 and 4, the enclosure 1 has an annular groove 5 intended to receive a seal 6 when it is in the mounted position.

Indeed, it is imperative in the use of such enclosures 1 to produce high-speed train electrical cabinets that the refrigerant circulates outside the enclosure 1 without being able to penetrate inside the latter.

In addition, whatever the conditions of use, linked to variations in temperature or mechanical stress such as vibrations, these enclosures 1 must always remain perfectly sealed. Any introduction, even minimal, of an unwanted external agent would have the consequence of damaging the power electronics and therefore of immobilizing the train.

On the smooth external surface 2 of the enclosure 1 are regularly spaced in a distribution a superposition of fins 7 according to the invention.

This distribution of fins 7 completely covers the heat exchange surface which corresponds to the part of the surface of the enclosure situated between the two ends 3 and 4.

Of course, this heat exchange surface can vary depending on the uses.

These fins 7 are made of a material identical to that of the enclosure 1, that is to say aluminum. However, depending on requirements, these fins could be made of any other type of metal or metal alloy such as in particular copper, copper-nickel alloy, carbon steel or stainless steel, etc.

These fins 7 are arranged in a helical winding whose pitch A is determined. The pitch A, is determined as being the distance separating two successive fins 7 as it is more particularly illustrated in FIG. 2.

The pitch A, which is a function of different parameters and in particular the desired thermal efficiency as well as the nature and the shape of the fins 7, is adapted according to the use.

However, it should be noted that, in the context of the application described, the pitch A and the number of fins which are on the enclosure 1 must be determined with precision. By way of example, the enclosure 1 must comprise 357 fins per meter with a tolerance of more or less 3 fins, that is to say that this enclosure 1 must comprise between 354 and 360 fins per meter.

In fact, in this type of application, it is desirable to have a precise number of fins 7 disposed on the smooth external surface of the enclosure 1 since it is impossible to make connections.

Any excessive drop in step A also has the consequence of causing a pressure drop and therefore of reducing the transmission of energy. calorific.

Furthermore, the spacing between each fin 7 if it is too large, may have the consequence of reducing the retention of the fins 7 between them as will be described later, as well as reducing the protection of the smooth external surface 2 of the enclosure 1 against corrosion.

Each fin 7, as more particularly illustrated in FIG. 3, has a body 10 which has a L-shaped cross-section. This body 10 has a foot 11 and a base 12 whose dimensions are variable depending on the proper dimension of the fins and desired use.

The base 12 has knurling 13 on at least part of its surface to allow tensioning and effective covering of each fin 7 by covering this knurling 13 with the lower part of the foot 11 of the adjacent fin 7.

In one embodiment, this knurling 13 is arranged on a part of the surface of the base 12 sufficient to ensure its effective recovery by the foot 11 of the adjacent fin on a covering surface corresponding substantially to the knurled surface.

This overlap ensures that the fins are held together on the smooth external surface 2 of the enclosure 1 corresponding to the entire surface of the heat exchange. This covering also ensures perfect mechanical strength which allows the enclosure to be used in all conditions.

In an alternative embodiment, to increase the mechanical retention of the fins 7 between them, on the outer surface 2 of the enclosure, the fins 7 have in cross section a shape of double L as more particularly shown in FIG. 4.

In this case, each fin 7 has a body 14 which comprises on the one hand a foot 15 and a base 16 covered by a base 17 and a foot 18 of the adjacent fin 7 and, on the other hand, a foot 19 and a base 20 intended to also cover a base and a foot of another fin 7.

The base 16 and the base 20 also have a knurling 22 disposed on a part of the surface in order to increase the maintenance under tension of the fins 7 between them.

Whatever the embodiment of the fins 7, they are adapted to have a large heat exchange surface which is maintained over time, as well as perfect mechanical strength of the fins 7 between them on the external surface 2 of the pregnant 1.

A surprising and unexpected aspect of the invention resides in the particular conformation of the fins as shown in FIG. 5.

Referring to FIG. 5, it can be seen that the base 24 has over its entire periphery substantially in the vicinity of the base 25 a regular distribution of radial ripples 26. This regular distribution of radial ripples 26 results, as will be described later, of the manufacturing process.

These corrugations 26 offer an important advantage by allowing improved circulation of the heat transfer fluid, in particular by the effects of turbulence and eddies, which makes it possible to increase the heat exchange efficiency.

The subject of the invention is also a method for producing the enclosures 1.

An important factor involved in the production of these enclosures 1 lies in the difficulty of placing the fins 7 under tension on a smooth enclosure of large diameter so that they mechanically hold together.

In addition, it is desirable that the tension exerted, during the fitting of the fins 7, is sufficient so that they are held in a coherent manner with one another and that they cannot shift relative to each other which whatever the conditions of use.

We make enclosure 1 with a large diameter whose external surface 2 is smooth over at least part of their total external surface corresponding to the heat exchange surface.

Then a metal strip 30 is continuously unrolled at a determined speed.

To ensure the positioning of the fins 7 under tension, on the smooth external surface 2 of the enclosure 1, the pressure exerted during the positioning of the fins 7 is regulated by exerting a sufficient tensile force on the metal strip. 30 during the formation of the body 10 of the fin 7 and of its knurling while also exerting a retaining action, synchronized or not, on the movement of the mechanical tape 30. These two actions combined, according to a force including intensity is controlled, ensuring that the fins 7 are tensioned on the external surface 2 of the enclosure 1.

The critical tension must in this case be reached in order to ensure an effective and homogeneous retention of the fins 7 as well as a precise adjustment of their position on the smooth external surface 2 of the enclosure 1.

Indeed, if an insufficient tension is exerted, the fins 7 are not sufficiently held together on the external surface 2 of the enclosure 1 so that they can separate during use. This separation is particularly frequent when these enclosures are subjected to significant mechanical or thermal stresses. This separation has the consequence of freeing an area from the surface 2 of the enclosure 1, which is therefore subject to corrosion. It follows that this corrosion can cause the formation of micro-cracks and therefore break the seal of the enclosure 1 which can lead to the stop of the operation of the high speed train.

Likewise, this separation of the fins 7 has the consequence of reducing the efficiency of the thermal efficiency of the enclosure.

Similarly, if too much tension is exerted on the metal strip 30, due to its small thickness, it deforms, and it is no longer possible to produce fins 7.

Then, by winding under pressure on the smooth external surface 2 of the enclosure 1 driven in a rotational movement, the fins 7 according to a distribution which here is helical. The speed of rotation of the enclosure 1 is determined in order to ensure a desired distribution according to a determined pitch of the fins 7.

To facilitate sufficient deformation of the metal, the metal is heated to an appropriate temperature by transmitting to the metal strip 30 sufficient heat energy during the operation of forming the body of the fin 7 and knurling the fin 7. For example, for aluminum, the metal strip is heated to a temperature between 20 and 50 ° C.

It should also be noted that the speed of rotation of the cylindrical enclosure 1 is linked with that of the unwinding of the metal strip 30. In fact, it is notably as a function of this speed of rotation of the enclosure 1 that the pitch A of the fin 7 is determined and that the correct positioning of the fins 7, that is to say the overlapping and partial overlapping of their foot and of the base is perfectly obtained to ensure that said fins 7 are kept under pressure.

Furthermore, a surprising unexpected aspect of this process lies in the shape of the fins. In fact, due to the tension exerted on the metal strip 30 during the tensioning of the fins 7 on the smooth external surface 2 of the enclosure 1, it appears on these fins 7, a radial distribution of undulations 26. This radial distribution of corrugations 26 promotes the turbulence flow of the fluids and therefore increases the heat exchange properties of the enclosure 1.

The invention also relates to a device for implementing the method.

This device comprises means 40 for producing the enclosure 1 of large diameter, the external surface 2 of which is smooth.

This device also includes means 41 for storing the metallic strip 30 in the form of a reel. These means 41 consist of a horizontal magazine 42, the dimensions of which may be adjustable as a function of those of the coil of metal tape 30. Of course, one could envisage the presence of several magazines of different sizes possibly superimposed or arranged side by side. Means 43 are provided for exerting traction on the metal strip 30 which runs continuously. These means 43 consist of a wheel 45 driven in rotation around a shaft actuated by motor members of a conventional type.

The speed of rotation of the wheel 45 and its size are adjustable by conventional means within the reach of ordinary skill in the art.

Means 46 for exerting a retention of the continuous scrolling of the metallic strip 30 are provided. These means 46 consist of two pressure rollers 47 inside which the metal strip 30 passes.

The drive of the rollers 47 is independent of that of the wheel 45, but the combined action of these rollers 47 and of the wheel 45 has the consequence that the traction exerted by the wheel 45 associated with the retention of the metallic strip 30 exerted by the pressure rollers 47 makes it possible to place the fin 7 on the enclosure according to a determined pressure and tension.

The device also has means 48 for forming the body 10 of the fin and for knurling this body 10. These means 48 are constituted here by the rollers 47 which have on a part of its surface in the vicinity of its periphery knurling and a horizontal support table. The passage of the metallic strip 30 on this horizontal table 49 and the combined action of the rollers 47 ensure both the formation of the body 10 of the fin in L or in double L as well as its knurling on a part of its surface.

The distribution and the dimension of the knurling, on a part of the surface of the body 10 of the fin 7 is of course adjustable to allow positioning and overlapping of the fins 7 ensuring satisfactory mechanical strength of the different fins 7 between them when they are energized on the external surface 2 of the enclosure 1.

Furthermore, the device has means 50 for holding the cylindrical enclosure 1. These means 50 consist of a mandrel 51 whose diameter is complementary to that of the enclosure 1. The mandrel 51 is driven by a regular rotational movement synchronized or not with that of the knurled wheel 45 in order to allow regular positioning of the fins 7 on the smooth external surface 2 of the enclosure 1.

In addition, the mandrel 51 is driven by a regular rotational movement synchronized or not with that of the knurled wheel 45 in order to allow the fins 7 to be put in place at a determined pitch A. Thus, for example, the speed of rotation of the mandrel 51 is 7 to 8 revolutions per minute. Of course, it is adjustable according to the desired step A.

To ensure a transmission of heat energy, the knurled wheel 45 comprises means such as an electrical conductor allowing the passage of a current, an electrical resistance 52 or any other equivalent device.

Thus, when the metal strip 30 passes in contact with the knurled wheel 45, it receives a certain amount of heat. It then becomes more malleable and can be more easily formed in L or double L.

Means 53 for controlling, regulating and synchronizing the operation of the device are also provided to ensure operation of the device under desired conditions of use.

Claims (10)

1. A cylindrical enclosure (1) for cooling by an external heat-transfer fluid, and comprising a smooth outer surface (2) at least partially covered by fins (7) distributed uniformly over said smooth outer surface (2) in a helical arrangement of determined pitch (A), each fin (7) having a body (10) which in cross-section has a substantially L-shaped configuration, comprising a foot (11) and a base (12) which are applied against the smooth outer surface (2), the fins (7) being wound under tension on said smooth outer surface (2) with a partial overlap such that their base (12) is partially covered by the foot (11) of the adjacent fin (7) on the corresponding side, characterised in that it has an axial dimension or height (H) and a diameter (D) such that the ratio H/D is between approximately 1.14 and approximately 5.33, and in that each fin (7) has a knurling (13) which extends over the surface of the part of the base (12) which is covered by the foot (11) of the adjacent fin (7).
2. A cylindrical enclosure (1) for cooling by an external heat-transfer fluid, and comprising a smooth outer surface (2) at least partially covered by fins (7) distributed uniformly over said smooth outer surface (2) in a helical arrangement of determined pitch (A), each fin (7) having a body (14) which in cross-section has a substantially double-L-shaped configuration, comprising a first foot (15) and a first base (16) which are applied against the smooth outer surface (2), the fins (7) being wound under tension on said smooth outer surface (2) with a partial overlap such that their first base (16) is at least partially covered by a second foot (18) and a second base (17) of the adjacent fin (7) on the corresponding side, characterised in that it has an axial dimension or height (H) and a diameter (D) such that the ratio H/D is between approximately 1.14 and approximately 5.33, and in that each fin (7) has, on a part of its first base (16), a first knurling (22) covered by the second base (17) of the adjacent fin (7) on the corresponding side, and in that said second base (17) has a second knurling (22) on the surface of its part which covers the knurling (22) presented by the covered first base (16) of the adjacent fin (7) on the other side.
3. An enclosure according to Claim 1 or 2, characterised in that the fins (7) have a uniform distribution of radial corrugations (26) on their body (10, 14).
4. An enclosure according to any one of Claims 1 to 3, characterised in that its height (H) is between 400 and 800 mm and its diameter (D) is between 150 and 350 mm.
5. An enclosure according to any one of Claims 1 to 4, characterised in that its smooth outer surface (2) has a heat-exchange zone covered by fins (7) and defined between two end zones (3, 4) each having an annular groove (5) receiving a gasket (6).
6. A method of producing a cylindrical enclosure (1) according to any one of Claims 1 to 5, wherein:

   - a cylindrical enclosure (1) is made, at least part of the outer surface (2) of which is smooth,

   - a metal strip (30) is continuously unwound at a determined speed; and then

   - traction is applied to the strip (30) when forming a body (10, 14) of a fin (7) having a cross-section of substantially L or double-L-shape while applying movement retention to the said strip (30),

   - fins (7) are arranged under tension in a helical distribution of determined pitch (A) over at least the smooth part of the outer surface (2) of the cylindrical enclosure (1), the speed of locating the fins (7) being synchronised with the speed of movement of the strip (30), characterised in that the said cylindrical enclosure (1) is made with an axial dimension or height (H) and a diameter (D) such that the ratio H/D is between approximately 1.14 and approximately 5.33, and

   - at least one knurling (13, 22) is made on a part of the strip (30) which is intended to form a part of a fin (7) covered by the next fin formed on the enclosure (1).
7. A method according to Claim 6, characterised in that heat energy is transmitted to the metal strip (30) to facilitate the formation of the body (10, 14) of the fin (7).
8. A method according to Claim 6 or 7, characterised in that the said knurling (13, 22) is effected at the same time as the said movement retention is applied to the strip (30).
9. Apparatus for performing the method according to any one of Claims 6 to 8, comprising

   - means (40) for forming a cylindrical enclosure (1), at least part of the outer surface (2) of which is smooth,

   - means (41) for storing a reel of metal strip (30),

   - means (43) for applying traction to the strip (30) at a determined speed,

   - means (46) for retaining the strip (30) coupled to the means (43) for applying traction to said strip,

   - means (50) for keeping the cylindrical enclosure (1) driven by rotary movement, and

   - means (48) for forming the strip (30) in the form of fins (7) of a cross-section of L or double-L shape, wound helically around said cylindrical enclosure (1), characterised in that the said means (40) for producing the enclosure (1) enable the latter to be formed with an axial dimension or height (H) and a diameter (D) such that the ratio H/D is between approximately 1.14 and approximately 5.33 and in that the apparatus also comprises means (45, 47) for knurling the strip (30) over at least a part intended to form a part of a fin (7) which is covered by the next fin (7) formed on the enclosure (1).
10. Apparatus according to Claim 9, characterised in that the said means (45, 47) for knurling the strip (30) have means common, firstly, with the means (43) for applying traction to the strip (30) and, secondly, with the means (48) for forming the strip (30), such common means respectively comprising, firstly, a knurled wheel (45) for applying traction to the strip and, secondly, two knurled presser rollers (47) for retaining the strip and co-operating with a horizontal table (49) for forming the body (10) of the fin (7).

Images