EP0687880A1 - Tube with a plurality of spiral ribs and method of manufacturing the same - Google Patents

Abstract

The invention relates to a metallic finned tube (1), in particular for heat exchangers or the like, with multi-start integral fins (2) that run around the outside in a helical manner, the n finned passages beginning at the beginning of the tube - evenly distributed over the circumference of the tube. The finned tube (1) is characterized in that at a rate n> = 4 at least one group is formed which has at least two adjacent starts (A1, A2 or A3, A4 ...) of finned passages. The method according to the invention ensures economical production of the finned tube (1) according to the invention. <IMAGE>

Description

The invention relates to a metallic finned tube, in particular for heat exchangers or the like; with helical circumferential, multi-start integral ribs on the outside (see, for example, DE-AS 2.110.485).

Finned tubes with single or multi-start fins running helically on the outside are rolled out of the tube wall by means of rolling tools which have roller disks arranged on tool shafts (cf. US Pat. Nos. 1,865,575 / 3,327,512 and Fig. 1).

While thread rolling on bars or thick-walled pipes often uses devices with two rolling tools arranged opposite one another, devices with three or four rolling tools evenly distributed around the pipe circumference are used for rolling finned pipes (see Fig. 2).

The transferable thermal performance of finned tubes depends, among other things, on the enlargement of the surface achieved by the fins. For this reason, the fin division of finned tubes has decreased continuously in recent years. As a result, the surface enlargement achieved by the ribbing could be increased further and further. With a rib pitch of 0.63 mm (corresponding to 1574 ribs per m), the surface is quadrupled compared to the smooth tube. In applications with phase change, ie in evaporators and condensers, surface forces and capillary-porous effects result in additional intensification of the heat transfer, in particular in the case of Pipes with small fin pitches reached.

The invention has for its object to improve the heat transfer performance of the known finned tubes, an economical production of the finned tubes must be ensured.

The object is achieved in that at a rate n ≧ 4 at least one group is formed which has at least two adjacent starts (A₁, A₂ or A₃, A₄ ...) of rib courses.

The economical production of the finned tube according to the invention is explained in connection with the method according to the invention.

According to preferred embodiments of the finned tube according to the invention, groups of two, three or four beginnings of finned passages are formed.

For example, in the case of a device with three rolling tools and a six-course rolling method, there are three groups, each with two adjacent starts of rib passes, as shown in FIG. 3a. In contrast to this, in the case of a device with six rolling tools, with six-course rolling, there would be six starts of rib courses (FIG. 3b).

The invention is particularly suitable for high-performance finned tubes in which the fin tips are compressed on the outside either to form thickened ends, are notched and possibly split after the notching to form cavities and / or are laterally bent and / or compressed.

In the finned tubes according to the invention, the fin pitch is preferably t _R = 0.25-1.50 mm and the fin height h _R ≦ 1.60 mm.

To intensify the heat transfer, the outside of the finned tubes designed according to the invention can be combined with different structures on the inside of the tube. It is preferably proposed that the inside has helical circumferential inner ribs, the division - measured perpendicular to the inner ribs - t _i = 0.5 - 3 mm, their height h _i = 0.2 - 0.5 mm and their pitch angle ϑ = 25 - 70 °.

According to a further embodiment of the invention, the pitch angle of the inner fins (9) ϑ = 5 - 25 °, the ratio of the height of the inner fins (9) to the inner diameter of the tube h _i / D _i = 0.02 - 0.03, the middle Flank distance of the inner fins (9) W = 0.15 - 40 mm and the apex angle of the inner fins γ = 30 - 60 ° (W and γ are measured in a section plane perpendicular to the pipe axis).

According to another alternative, the inside has corrugations, which can also be interrupted and whose spacing - viewed in the longitudinal direction of the tube - preferably corresponds to the product of the fin pitch t _R and pitch n.

Furthermore, protrusions are recommended on the inside, which are formed by two intersecting systems of oppositely helical inner trains.

The invention further relates to a method for producing the finned tube according to the invention.

wobei w_walz die Walzgeschwindigkeit, α der Schrägstellungswinkel, D_sch der Durchmesser der größten Walzscheibe und ω die Drehzahl der Werkzeugwellen ist.The fins were originally rolled on the outside of a finned tube. To increase the output of a rolling device, a consideration of the Relationship for the rolling speed w _roll . The rolling speed is calculated from: $${\text{w}}_{\text{roll}}{\text{= π. tan (α). D}}_{\text{sh}}\text{. ω Eq.}$$

where w _{roll is} the rolling speed, α is the inclination angle, D _{sch is} the diameter of the largest rolling disk and ω is the speed of the tool shafts.

There are technical limits to increasing the speed ω. D _sch are geometrical limits; because the maximum diameter results from the condition that the roller disks of adjacent tool shafts must not touch during operation.

wobei n die Gängigkeit, t_R die Rippenteilung und D_Kern der Kerndurchmesser des Rippenrohres ist. Demnach läßt sich bei vorgegebener Rippengeometrie (Teilung und Kerndurchmesser) die Schrägstellung nur durch Erhöhung der Gängigkeit vergrößern.An increase in w _roll can therefore only be achieved via the inclination angle α. The following applies to tan α:

where n is the movement rate, _R t is the pitch of the ribs and D _core, the core diameter of the finned tube is. Accordingly, for a given rib geometry (pitch and core diameter), the inclination can only be increased by increasing the pitch.

First, two-start finned tubes were rolled on rolling devices with three rolling tools (see US Pat. No. 3,383,893).

Later, three-speed rolling was carried out on such devices (cf. US Pat. No. 3,481,394). This patent also mentions the possibility of rolling with six threads when using devices with six rolling tools. It is characteristic of the prior art that either all the rolling tools run in a common rib gear (single and double-start rolling) or, in the limit case, each rolling tool forms its own rib gear (three- or four-gear rolling). A limit was reached because of that it was assumed that each rolling tool can produce a maximum of one rib gear.

Starting from a method according to the preamble of claim 16 (cf. DE-AS 2.110.485), the method according to the invention is characterized in that the desired movement n of the existing number N of rolling tools is adapted in such a way that one or more of the rolling tools each more generate as a ribbed duct; d. H. it is always n> N.

The wording "and / or" in the preamble of claim 16 relates to whether the tube should rotate at the same time as the axial feed movement or not.

The method according to the invention is based on the fact that at least one rolling tool is used to produce more than one rib gear. The ability to roll finned tubes is thus increased considerably beyond what was previously possible. The present invention enables the output of rolling devices to be multiplied. The maximum limit of the movement is the achievable inclination angles of the devices, apart from the self-locking. According to special embodiments of the method according to the invention, each rolling tool produces two, three or four rib courses.

A method according to claim 20 is recommended for producing a finned tube with compressed fin tips, a method according to claim 21 for producing a finned tube with notched finned tips and one according to claim 22 for producing a finned tube with split and / or bent and / or compressed finned tips.

The use of a profiled rolling mandrel is recommended for producing a finned tube according to the invention with inner fins. To produce an inventive A method according to claim 24 is proposed for finned tube with inner corrugations (cf. also EPS 0.102.407). In order to prevent the adjacent corrugations on the inside of the tube from being too close together in the case of the fine fin divisions, it is recommended that a corrugated washer is not used in all rolling tools.

The invention is explained in more detail using the following exemplary embodiments.

1 schematically shows an integral finned tube 1 according to the invention, on the outside of which fins 2 run helically, between which a groove 3 is formed. The ribs 2 have a height h _R ; the rib division (distance from center of rib to center of rib) is denoted by t _R.

The finned tube 1 according to the invention is produced by a rolling process (cf. US Pat. Nos. 1,865,575 / 3,327,512) using the device shown in FIGS. 1 and 2b.

A device is used which consists of N = 4 tool holders 4 (4₁ / 4₂ / 4₃ / 4₄), in each of which a rolling tool 5 is integrated (only one tool holder 4 is shown in FIG. 1, but three or more than four tool holders 4 are used). The tool holders 4 are each offset by β = 360 ° / N on the circumference of the finned tube 1. The tool holder 4 can be adjusted radially. They are in turn arranged in a stationary roller head (not shown) (according to another variant, the tube is only advanced axially when the roller head is rotating).

The smooth pipe 1 'entering the device in the direction of the arrow is set in rotation by the driven rolling tools 5 arranged on the circumference, the shafts 6 of the rolling tools 5 running obliquely to the pipe axis. Of the Inclination angle α of the shafts 6 is determined according to the desired pitch n according to Eq. (2) set. The rolling tools 5 consist, in a manner known per se, of a plurality of rolling disks 7 arranged side by side on the shafts 6, the diameter of which increases in the direction of the arrow. The centrally arranged rolling tools 5 form the helically surrounding ribs 2 from the tube wall of the smooth tube 1 ', the smooth tube 1' being supported here by a profiled rolling mandrel 8. As a result, the ribs, which are denoted by the number 9, are formed on the inside of the tube 1 in the form of a spiral.

The rolling process can be clearly identified at the start of the pipe or at the transition pieces between finned and non-finned pipe sections, since the rolling disc is engaged in groups when immersed in the pipe wall. Fig. 3 shows schematically the difference between the inventive and conventional rolling method using the example of six-speed rolling. According to Fig. 3a, three groups of two adjacent beginnings A₁, A₂ or A₃, A₄ or A₅, A₆ (the latter not shown) of fins are distributed evenly over the circumference of the tube, while according to Fig. 3b six individual beginnings A₁, A₂, A₃, A₄, A₅, A₆ (A₄ - A₆ not shown) are arranged on the pipe circumference. (For the rest, the previous reference numbers, some of which are provided with indices, are used in FIGS. 3a, 3b.)

Numerical example:

According to the described method, finned tubes 1 with a fin pitch t _R ≈ 0.53 mm were produced on a device with four rolling tools 5 in eight threads. The fin diameter for this type of tube is D = 19 mm, the fin height h _R = 0.95 mm. On the inside of the finned tube, a helical inner finned structure was created in the same work step with about 40 inner fins 9, which run at an angle of inclination ϑ = 45 ° to the tube axis.

Another implementation is based on the eight-thread rolling of a finned tube 1 with a pitch t _R ≈ 0.64 mm with a similar internal structure as described above.

FIG. 4 shows, in addition to FIG. 1, a rolling device in which a swaging disk 10 is additionally integrated in the tool holder 4 for upsetting into T-shaped rib tips 2 '.

To explain the internal structure of the tube 1, FIG. 5 shows a partial section perpendicular to the tube axis, in which the sizes rib diameter D, inner diameter D _i , rib height h _i , average flank spacing W and the apex angle γ of the inner ribs 9 are entered.

Claims (25)

Metallic finned tube (1), in particular for heat exchangers or the like, with on the outside helical circumferential, multi-start integral fins (2), which are described, among other things, by the sizes n, finned pitch t _R and fin height h _R , the n fins on Start the pipe - evenly distributed over the pipe circumference -
characterized,
that at a rate n ≧ 4 at least one group is formed which has at least two adjacent starts (A₁, A₂ or A₃, A₄ ...) of rib courses. Finned tube according to claim 1, characterized in
that groups of 2 beginnings of rib courses are formed. Finned tube according to claim 1, characterized in
that groups of 3 beginnings of rib corridors are formed. Finned tube according to claim 1, characterized in
that groups of 4 beginnings of rib courses are formed. Finned tube according to one or more of claims 1-4, characterized in
that the rib tips (2 ') are compressed to form thickened ends. Finned tube according to one or more of claims 1-4, characterized in
that the rib tips (2 ') are notched. Finned tube according to claim 6, characterized in
that the rib tips (2 ') are split to form cavities and / or laterally bent and / or compressed. Finned tube according to one or more of claims 1-7, characterized in that
that the rib pitch t _R = 0.25 - 1.50 mm and the rib height h _R ≦ 1.60 mm. Finned tube according to one or more of claims 1-8, characterized in
that it has helical inner ribs (9). Finned tube according to claim 9, characterized in
that the division of the inner ribs (9) - measured perpendicular to the inner ribs (9) - t _i = 0.5 - 3 mm, the height of the inner ribs (9) h _i = 0.2 - 0.5 mm and the pitch angle of the Inner ribs (9) ϑ = 25 - 70 °. Finned tube according to claim 9, characterized in
that the pitch angle of the inner fins (9) ϑ = 5 - 25 °, the ratio of the height of the inner fins (9) to the inner diameter of the tube h _i / D _i = 0.02 - 0.03, the mean flank spacing of the inner fins (9) W = 0.15 - 0.40 mm and the apex angle of the inner ribs γ = 30 - 60 °. Finned tube according to one or more of claims 1-8, characterized in
that the inside has corrugations. Finned tube according to claim 12, characterized in
that the corrugations are interrupted. Finned tube according to claim 12 or 13, characterized in that
that the axial spacing of the corrugations corresponds to the product of rib pitch t _R and pitch n. Finned tube according to one or more of claims 1-8, characterized in
that it has projections on the inside, which are formed by two intersecting systems of oppositely helical inner trains. Method for producing a finned tube according to one or more of claims 1-4, in which the following method steps are carried out: a) on the outer surface of a smooth tube (1 '), helical ribs (2) are rolled out, in that the rib material is obtained by displacing material from the tube wall to the outside by means of a rolling process, b) the rolling process is carried out with at least one rolling tool (5) lying against the pipe, which consists of a plurality of adjacent rolling disks (7) with different diameters, which can be pressed radially into the pipe wall and whose shafts (6) during the rib production under a predetermined, the desired pitch n corresponding inclination angle α with respect to the tube axis are arranged, c) the smooth tube (1 ') is supported by a rolling mandrel (8) located therein, d) the resulting finned tube (1) is set in rotation by the rolling forces and / or advanced according to the fins (2) being formed, the fins (2) being formed from the otherwise undeformed smooth tube (1 ') with increasing height,
characterized by the following process step: e) the desired movement n is adapted to the existing number N of the rolling tools (5) in such a way that one or more of the rolling tools (5) each produce more than one rib gear. A method according to claim 16 for producing a finned tube according to claim 2, characterized in that
that each rolling tool (5) produces two rib courses. A method according to claim 16 for producing a finned tube according to claim 3, characterized in that
that each rolling tool (5) produces three rib courses. A method according to claim 16 for producing a
Finned tube according to claim 4, characterized in that each rolling tool (5) produces four fins. Method according to one or more of claims 16-19 for producing a finned tube according to claim 5,
characterized,
that the rib tips (2 ') are deformed in at least one step by radial forces. Method according to one or more of claims 16-19 for producing a finned tube according to claim 6,
characterized,
that notches are pressed into the rib tips (2 ') by at least one notch disk (10). A method according to claim 21 for producing a finned tube according to claim 7, characterized in that
that the rib tips (2 ') split in the direction of the ribs (2) and / or bent by axial forces and / or deformed by radial forces. Method according to one or more of claims 16-22 for producing a finned tube according to one or more of claims 9-11, characterized in that
that the smooth tube (1 ') is supported by a profiled rolling mandrel (8). Method according to one or more of claims 16-22 for producing a finned tube according to claim 12 or 13, characterized in that
that after the formation of the ribs (2), the groove (3) between the ribs (2) is pressed continuously or only in places by radial forces, with no support being provided by an internal mandrel in this area, so that tube wall material to form Corrugations are shifted to the inside of the pipe. A method according to claim 24 for producing a finned tube according to claim 15, characterized in that
that not all the rolling tools (5) used are assigned a corrugated washer.

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