FR2631269A1 - METHOD FOR MANUFACTURING FIN TUBES WITH HIGH THERMAL EXCHANGE COEFFICIENT - Google Patents

Abstract

Method for manufacturing finned tubes with a high heat exchange coefficient, in which the tube 1 to be fitted with fins, while it is in rotation and straight forward movement, is subjected successively and separately to an operation of surface notch and deformation and lifting of the partially detached part.

Description

- 1-

  METHOD FOR MANUFACTURING COEFFICIENT FIN TUBES

HIGH THERMAL EXCHANGE.

  The present invention relates to a manufacturing process

  finned tubes with high heat exchange coefficient.

  More particularly, the present invention refers to a method of manufacturing finned tubes with a high heat exchange coefficient suitable for use in

heat exchangers.

  As is known, various processes can be used for the production of finned tubes for heat exchangers.

heat.

  One method is to wrap around a cylindrical tube

  smooths a strip of thin sheet metal arranged in a spiral. This process

  not only is quite complex and therefore expensive, but also has the disadvantage that contact

  between the tube and the fin is not done on the entire sur-

face of the tube.

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  - 2 - In addition, on the surface of the tube and / or on the surface of the sheet which comes into contact with the tube, there is a layer, even thin, of oxide, so that the conductivity

is not insured.

  Another method is to pass the smooth tube,

  thicker than that required, through a very

  spinner, spiral movement. The ductile material of the tube is thus crushed and reassembled out of the shaped mold

  of spiral fins. This process results in a great waste

  lage of material, the fact that the fins can not be thin, and the thermal efficiency of the fin tube

  obtained is not very satisfactory.

  In addition, the process is rather complex to implement and, consequently, expensive, since it requires

  inserting a metal bar into the tube to prevent

  expensive crushing of the tube itself during work, under the effect of the pressure exerted, and then the removal of

this bar.

  Another rather simple and economical process for manufacturing

  quer finned tubes for heat exchangers, is that described in Italian Patent No. 748709 filed January 13, 1965 and issued February 15, 1967. This process involves making one or more circular or helical cuts in an inclined direction relative to the axis of the tube, on the external surface of the tube itself, and at the same time or successively to the notch operation, to be deformed and folded outwards, relative to the external surface of the tube, the portion of material isolated from the rest of the material in the tube. The notch created on the surface

  external of the tube has a direction of penetration into the ma-

  substantially inclined relative to the axis of the tube itself

  similarly, by isolating from the rest of the material, without however completely detaching it, portions of material having the shape of a crest placed along the external surface of the tube. Parallel to the notching operation, using the same tool, the partially insulated portions of material are deformed and folded outwards, relative to the external surface of the tube, so as to overflow as much as possible.

  relative to it, and constitute a fin.

  A tool suitable for carrying out at the same time the cutting and the outward folding of the partially insulated material in the form of a thin sheet arranged helically around the tube, is described in Italian patent application No. 22798 A / 85 filed on 12 November 1985. The tool described in this application comprises a cutting line composed of two portions, connected to each other, one of which with a cutting function which first meets the moving surface of the tube and presents itself , relative to it and its generators, in an inclined position at an angle which

  goes from 0 to 90, and the other, having a deformation function

  tion of the chip which abandons the last contact with the fin obtained from the tube, delimits a portion of

  surface of the tool, the points of which, by the relative movement

  tif compared to the fin, are driven by relative speeds

  direct ves tangentially both to said surface of

  the tool only on the surface of the fin at the contact points.

  The tool is driven in a helical movement relative to the axis of the tube. This can be obtained by imparting to the tube a rotary movement around its axis - and with the tool a uniform rectilinear movement parallel to the axis of the tube. As a variant, the tube can be kept in rectilinear movement

  uniform along its axis and the tool in uniform rotary movement

  shape around its own axis. The tube is kept at

  ximity of the tool by means of a centering and precision positioning member, rigidly fixed to the structure

carrying the tools.

2 6 3 1 2 6 9

  -4- This process, even if it has had some industrial success, has certain practical drawbacks due both to the wear of the tool which must be continually replaced, and to its

  construction which requires very specialized personnel.

  The object of the present invention is to provide a method of manufacturing finned tubes with a high heat exchange coefficient, where the fins are obtained from a

  single piece of tube, and which does not have the disadvantages

nients indicated above.

  More particularly, the object of the invention is to provide a method which allows the finning of the tubes by notching, deformation and outward folding of partially isolated material in the form of a thin sheet arranged in a helix, simple, economical and

easy to make.

  According to the present invention, this objective and others are achieved by means of a method which consists of: a. to impart to the tube a rotational movement with respect to its axis and a rectilinear movement parallel to its axis, with, for each revolution, an axial rectilinear displacement of the tube equal to the desired pitch of the fin; b. performing the notching operation of the tube separately from that of producing fins; vs. to perform the operations of incision and production of fins in the opposite position relative to the axis of the tube; and D. to allow, during the notching and finning operations, a displacement of the tube, according to

  a segment equal to the depth of the cut, parallel to

to its axis of rotation.

  -5- The tools for notching and making fins are fixed on supports preferably arranged in position

  opposite and symmetrical with respect to the axis of the tube.

  Said supports are brought closer to the tube to be fitted with fins and adjusted so as to cut the tube to a depth

  equal to the desired height for the fins.

  The cutting tool can be of any type already known, and is oriented relative to the surfaces of the tube so that the notch is inclined and has an angle

  between 5 and 80 relative to the axis of the tube.

  The fin manufacturing tool has its curved and inclined surface so as to be able to penetrate into the slot previously formed by the notch, deform and bend, in a plane substantially perpendicular to the tube, the insulated chip so as to protrude as much as possible. from the surface of the

  tube, and to constitute a fin of suitable proportions

  bles fixed to the surface of said tube.

  It is preferable that the notch and fin production tools are placed in the opposite position and on the

  same axis with respect to the tube to be fitted with fins; in varian-

  te, said tools can be arranged in opposite position

  and axially separated by a distance of at least at least

not gash.

  According to an essential aspect of the present invention, the tube to be provided with fins is guided and supported by a support located near the notch and tools. production of fins and which, during work, keeps the tube in position, without excessive deformation, and which allows the

  tube to slide axially and rotate in said support.

  263t269 - 6 - This support consists of a socket, preferably made of hard material and special anti-friction, introduced and blocked

  in a housing fixed to the tool holder structure.

  Said socket is provided with a corresponding lateral opening.

  weight of which is arranged the notch tool and an elliptical hole whose largest diameter is disposed along the axis passing between the incision tool and that of

fin production.

  The process for manufacturing the finned tubes, object of the present invention, can be better understood thanks to the

  following detailed description referring to the drawing

  annexed, which represents an embodiment of the pre-

  invention, given by way of example, but not

limiting ...

  In the drawing: FIG. 1 represents the schematic front view of the device for notching and production of fins which implements the method of the present invention; 2 shows a schematic top view of the longitudinal section of Figure 1, obtained along a plane passing between the axis of the tube and the notch point;

  Figure 3 shows a schematic perspective view

  tive of the tool used to make the notch;

  Figure 4 shows a schematic perspective view

  tive of the crest deformation and lifting tool; and - 7 -

  Figure 5 shows a schematic perspective view

  tive of the tube support and guide sleeve.

  In the figures, the tube 1, which is smooth to provide with fins, is kept in rectilinear advance movement and of rotation about its own axis by motor members, not illus-

  very on the figures because they are of known type.

  The tube 1, smooth with fins, is passed through the elliptical hole 2 of a guide sleeve 3

  fixed to the frame 4 of the machine, by means of a fixing screw

  tion 5. The difference between the two radii dl and d2 of hole 2 is equal to the desired depth of the notch. The

  socket 3 is provided with a longitudinal slot 6, corresponding

  weight of which the notch tool 7 is inserted, and of a groove 13 in correspondence of which the fin tool 10 is inserted. Said notch tool 7 is fixed to a support 8 integral with a system of sliding guide 9

  which allows the displacement of the tool 7 for its approximation-

and its distance from the tube 1.

  In the opposite position to the notch tool 7, relative to the axis of rotation and advance of the tube 1, is arranged the tool

  fin production or deformation and lifting

  of the cut portion. Said tool 10 is fixed to a support 11 secured to a sliding guide system 12

  which allows the displacement of the tool 10 for its approximation-

and its distance from the tube 1.

  The tools for the notch 7 and the production of fins 10 are arranged so that the tube 1 is first notched and successively the detached portions are

  deformed and lifted to form the fins.

  The process for manufacturing finned tubes, object of the present invention, consists in introducing the tube 1 to be provided -8-

  fins, in the hole 2 of the guide sleeve 3.

  Successively, the two notch 7 and lifting tools

  ment 10 are adjusted so that they are placed in the opposite position and in contact with the external surface of the tube 1. The tube 1 is then rotated along its axis

  and it is moved axially at a corresponding speed

  you at the pace of the desired fin. While the tube is rotating, the notch tool 7 is pushed against the tube along a segment corresponding to the desired depth of

the notch.

  The height of the fins depends on the inclination of the tool

  notch relative to the axis of the tube.

  Along the external surface of the tube 1, a continuous helical notch is thus produced which detaches a portion of

  material without, however, detaching it completely.

  By effect of the notch force and the pressure exerted

  by the fin production tool 7, the tube 1 is moved

  axially so that the tool 10 fits into the helical groove of notch. Such axial displacement is regulated by the elliptical shape of the hole 2. The tool 10 deforms and folds outward relative to the surface

  outside of tube 1, the partially detachable portion of material

  from the rotating tube 1, forming the helical fin

continuous dal of the tube itself.

  The tube 1 can be made of copper, aluminum or any other

ductile and conductive material.

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Claims (6)

Claims   1. Method of manufacturing high finned tubes   heat exchange coefficient where the fins are obtained   bare on the surface of the tube (1) by a helical notch of a portion of material, without complete detachment thereof, and deformation and folding towards the outside, relative to the external surface of the tube, of the drifting portion of the notch operation, characterized in that, during the fin formation operation, the tube is kept in rotary movement around its axis and in rectilinear movement parallel to its axis, with a corresponding axial rectilinear displacement at   not desired fin; the notch operation is performed   killed separately from the deformation and outward folding operation of the cut portion; the two notch and folding operations are opposite with respect to the axis of the tube, and it is possible to move the tube parallel to its axis of rotation over a distance   corresponding to the depth of the notch.   2. Process according to claim 1, characterized in that the tube is guided and supported by a sleeve provided with an elliptical hole, where the difference between the two diameters is equal to the desired depth of notch. 3. Method according to claim 2, ccaractérisé in that the sleeve is provided with a longitudinal slot in correspondence of which is installed the notch tool.   4. Method according to one of the preceding claims,   characterized by the fact that the notching and deformation and outward folding means are fixed on - 10 -   sliding guide systems which allow them to be   and their distance from the tube to be fitted with fins.   5. Method according to one of the preceding claims,   characterized by the fact that the notching and finning tools are placed in the opposite position and on   the same axis with respect to the tube to be fitted with fins.   6. Method according to one of claims 1 to 4,   characterized in that the notch and fin forming tools are placed in opposite position and axially separated by a distance equal to at least one..not of the notch.