Method for connecting tubes of a shell and tube heat exchanger to a tube bottom of the shell and tube heat exchanger

Abstract

The present invention relates to a method for connecting tubes (221) of a shell and tube heat exchanger (200) to a tube bottom (230) of the shell and tube heat exchanger (200), wherein the tubes (221) and the tube bottom (230) are each made of aluminum or an aluminum alloy, and wherein the tubes (221) are connected to the tube bottom (230) by means of laser welding in a bonded manner.

Claims

1. A method for connecting tubes of a shell and tube heat exchanger to a tubesheet of the shell and tube heat exchanger, said method comprising: providing tubes and said tubesheet produced from aluminum or an aluminum alloy, wherein the tubes have in each case a maximum wall thickness of 2.0 mm and wherein the tubesheet has a thickness between 100 mm and 200 mm, and connecting said tubes to said tubesheet in a material-bonding manner by means of laser welding using a laser beam, wherein said laser beam during said laser welding has an intensity above 1 MW/cm.sup.2.

2. The method as claimed in claim 1, wherein the laser beam during said laser welding has an intensity above 2 MW/cm.sup.2.

3. The method as claimed in claim 1, wherein the tubes and/or the tubesheet respectively have a thermal conductivity between 10 W/mK and 140 W/mK.

4. The method as claimed in claim 1, wherein the tubes and/or the tubesheet are respectively produced from an alloy of aluminum that contains magnesium, manganese, silicon and/or copper.

5. The method as claimed in claim 1, wherein the laser beam during said laser welding has an intensity above 4 MW/cm.sup.2.

6. The method as claimed in claim 1, wherein the tubes and the tubesheet each have a thermal conductivity between 10 W/mK and 140 W/mK.

7. The method as claimed in claim 1, wherein the tubes and/or the tubesheet are respectively produced from an alloy of aluminum containing between 4.0% and 4.9% magnesium.

8. The method as claimed in claim 1, wherein the tubes and/or the tubesheet are respectively produced from an alloy of aluminum containing between 0.4% and 1.0% manganese.

9. The method as claimed in claim 1, wherein the tubes and/or the tubesheet are respectively produced from an AlMgSiCu alloy.

10. The method as claimed in claim 1, wherein the tubes and/or the tubesheet are respectively produced from an aluminum alloy containing at most 0.15% manganese, between 0.8% and 1.2% magnesium, between 0.4% and 0.8% silicon, and between 0.15% and 0.4% copper.

11. The method as claimed in claim 1, wherein the tubes and/or the tubesheet are respectively produced from an AlMgSi alloy.

12. The method as claimed in claim 1, wherein the tubes and/or the tubesheet are respectively produced from an aluminum alloy containing at most 0.1%, between 0.45% and 0.9% magnesium, between 0.2% and 0.6% silicon, and at most 0.1% copper.

13. The method as claimed in claim 1, wherein the laser beam is focused by means of optical elements.

14. The method as claimed in claim 13, wherein the laser beam is guided by means of an optical waveguide.

15. The method as claimed in claim 13, wherein the laser beam is produced by a fiber laser, a diode laser or a solid-state laser.

16. The method as claimed in claim 13, wherein the laser beam is guided by means of a fiber-optic cable.

17. The method as claimed in claim 1, wherein, before the laser welding, the tubes of the shell and tube heat exchanger are connected in a form-fitting manner to the tubesheet of the shell and tube heat exchanger.

18. The method as claimed in claim 17, wherein a first tubesheet is arranged at a first end of a core tube of the shell and tube heat exchanger and wherein a second tubesheet is arranged at a second end of the core tube, each of the tubes has a first end and a second end, the first end of each of the tubes is introduced into a bore in the first tubesheet, the tubes are coiled around the core tube, the second end of each of the tubes coiled around the core tube is introduced into a bore in the second tubesheet, and subsequently the tubes are connected to the first tubesheet and to the second tubesheet in a material-bonding manner by means of laser welding.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIGS. 1a and 1b are, respectively, sectional and perspective views of a preferred configuration of a shell and tube heat exchanger which has been produced by means of a preferred embodiment of a method according to the invention.

(2) FIGS. 2a and 2b are, respectively, sectional and perspective views of a further preferred configuration of a shell and tube heat exchanger which has been produced by means of a preferred embodiment of a method according to the invention.

(3) FIG. 3 schematically shows a device which is designed to carry out a preferred embodiment of a method according to the invention.

(4) In FIGS. 1a and 1b, a preferred configuration of a shell and tube heat exchanger is schematically shown and denoted by 100. In FIG. 1a, the shell and tube heat exchanger 100 is shown in a sectional view. In this example, the shell and tube heat exchanger 100 is formed as a straight-tube heat exchanger.

(5) The straight-tube heat exchanger 100 has a shell 110, which has a fluid inlet 111 and a fluid outlet 112 in order to pass a first fluid through the shell 110.

(6) Arranged within the shell 110 is a bundle of tubes 120 comprising a multiplicity of straight-running tubes 121. A second fluid may be passed through the tubes. The individual tubes 121 are connected in a material-bonding manner to tubesheets 130 of the straight-tube heat exchanger 100. The tubesheets 130 may for example be fastened to the ends of the shell 110.

(7) The straight-tube heat exchanger 100, the tubes 121 and the tubesheets 130 are produced from an aluminum alloy, in particular from an aluminum-magnesium-manganese alloy. For example, the tubes 120 and the tubesheets 130 are produced from the material EN AW-5083 or EN AW-AlMg4.5Mn0.7 with the material number DIN 3.3547, that is to say from an aluminum alloy with a proportion of manganese of between 0.4% and 1.0% and with a proportion of magnesium of between 4.0% and 4.9%.

(8) In FIG. 1b, part of the straight-tube heat exchanger 100 from FIG. 1a is shown in a perspective view. In FIG. 1b, only the bundle of tubes 120 and the tubesheets 130 are shown.

(9) As can be seen in FIG. 1b, the tubesheets 130 have bores 132. These bores 132 are arranged in a bore region 131 of the respective tubesheet 130. Each of the tubes 121 of the bundle of tubes 120 is connected in a material-bonding manner to the respective tubesheet 130 at one of these bores 132. In the course of a production process, these material-bonding tube-tubesheet connections are produced by means of laser welding, as described in detail further below with reference to FIG. 3.

(10) In FIGS. 2a and 2b, a further preferred configuration of a shell and tube heat exchanger is schematically shown and denoted by 200. In FIG. 2a, the shell and tube heat exchanger 200 analogous to FIG. 2a is shown in a sectional view. The shell and tube heat exchanger 200 is formed for example as a helically coiled shell and tube heat exchanger.

(11) By analogy with the straight-tube heat exchanger 100 from FIGS. 1a and 1b, the helically coiled shell and tube heat exchanger 200 also has a shell 210 with a fluid inlet 211 and a fluid outlet 212, arranged in the interior of which is a bundle of tubes 220 comprising a multiplicity of tubes 221.

(12) By contrast with the straight-tube heat exchanger 100, the tubes 210 of the helically coiled shell and tube heat exchanger 200 do not run in a straight line, but are coiled helically around a core tube 240. Tubesheets 230 of the helically coiled shell and tube heat exchanger 200 have along their circumference bore regions 231 with bores 232, each of the tubes 221 of the bundle of tubes 220 being connected in a material-bonding manner to the respective tubesheet 230 at one of these bores 232.

(13) The tubes 221 and tubesheets 230 are also preferably produced from an aluminum alloy, for example from the material EN AW-5083 or EN AW-AlMg4.5Mn0.7.

(14) In FIG. 2b, part of the helically coiled shell and tube heat exchanger 200 (the bundle of tubes 220, the tubesheets 230 and the core tube 240) from FIG. 2a is shown in a perspective view. As can be seen in FIG. 2b, the tubesheets 230 are fastened to the core tube 240 for example by way of supporting arms 233.

(15) In FIG. 3, a device which is designed to carry out a preferred embodiment of a method according to the invention is schematically shown.

(16) In FIG. 3, it is shown by way of example how with this device the tubes 221 are connected in a material-bonding manner to one of the tubesheets 230 of the helically coiled shell and tube heat exchanger 200 according to FIGS. 2a and 2b in the course of a production process.

(17) The device comprises a laser welding unit 300. A laser 310, for example an Nd:YAG laser, produces a laser beam 311, which can be focused by means of a focusing optical system 320 comprising expedient optical elements onto a location to be welded on the tubesheet 230. The focusing optical system 320 may for example have concave mirrors, which focus the laser beam 311 onto the location to be welded.

(18) A control unit 330 is designed to activate the laser 310 and the focusing optical system 320, in particular to move the laser beam 311 along and reposition and refocus it on the tubesheet. The control unit 330 provides automated control of the laser welding and allows automated production of the tube-tubesheet connections.

(19) It goes without saying that the device can also be used in an analogous way for producing the material-bonding connection between the tubes 122 and the tubesheets 130 of the straight-tube heat exchanger 100 according to FIGS. 1a and 1b, or generally for producing a material-bonding connection between tubes and tubesheets of some other shell and tube heat exchanger.

LIST OF REFERENCE NUMERALS

(20) 100 Shell and tube heat exchanger, straight-tube heat exchanger 110 Shell 111 Fluid inlet 112 Fluid outlet 120 Bundle of tubes 121 Tubes 130 Tubesheets 131 Bore region 132 Bores 200 Shell and tube heat exchanger, helically coiled shell and tube heat exchanger 210 Shell 211 Fluid inlet 212 Fluid outlet 220 Bundle of tubes 221 Tubes 230 Tubesheets 231 Bore region 232 Bores 233 Supporting arms 240 Core tube 300 Laser welding unit 310 Laser, Nd:YAG laser 311 Laser beam 320 Focusing optical system 330 Control unit