WO2020253992A1

WO2020253992A1 - Thermal prestressing for the bundled tubes of a wound heat transfer system

Info

Publication number: WO2020253992A1
Application number: PCT/EP2020/025288
Authority: WO
Inventors: Herbert Aigner; Manfred Schönberger; Christian Michael HERWERTH
Original assignee: Linde Gmbh
Priority date: 2019-06-21
Filing date: 2020-06-17
Publication date: 2020-12-24

Abstract

The invention relates to a method for winding at least one tube (20) onto a core tube (21) of a wound heat transfer system (1), the at least one tube (20) being wound helically onto the core tube (21), by rotating the core (21) about its longitudinal axis (z); during winding of the at least one tube (20) a portion (20a) of the at least one tube (20) to be wound onto the core tube (21) is heated by a heating device (34) and/or is bent mechanically, so that the at least one tube (20) is prestressed.

Description

description

Thermal prestress for the bundle tubes of a wound heat exchanger

The invention relates to a method for winding at least one tube onto a core tube which is intended for a wound heat exchanger.

Such a wound heat exchanger has a jacket which extends along a preferably vertically oriented longitudinal axis and delimits a jacket space for receiving a first fluid. A tube bundle with a plurality of tubes for receiving at least one second fluid is arranged in the jacket space, the tubes each being wound at least in sections helically on a core tube that extends in the jacket space along or coaxially to the longitudinal axis. Through this, several tube layers are formed which are arranged one above the other in the radial direction of the core tube or the tube bundle, so that the tube bundle (in relation to the radial direction) has an innermost tube layer that is arranged adjacent to the core tube, as well as an outermost tube layer that is the radial direction is arranged further away from the core tube and in particular encloses the innermost tube layer (and possibly the tube layers provided in between). The at least one second fluid can thus enter into an indirect heat exchange with the first fluid guided in the shell space.

In a method for winding such tubes onto the core tube, the core tube is generally clamped in a suitable device and rotated about its longitudinal axis. A tube attached to the core tube with one end or otherwise suitably attached to the core tube can be wound onto the core tube in a helical or helical manner, whereby it is suitably guided along the longitudinal axis of the core tube, so that the respective tube is ultimately opened by rotating the core tube the core tube or onto a tube layer already wound onto the core tube and spacers arranged and fixed thereon. The spacers are preferably designed as elongated webs, the tubes being fixed to the webs, for example by means of brackets. When winding wound heat exchangers, it is particularly important to wind the tubes around the core tube or the winding body in a prestressed manner. This tube prestressing primarily serves to ensure the cohesion of the wound body. This also applies in particular if the pre-tensioning decreases due to additionally wound pipe layers. Up to now, the pipe pre-tensioning has been applied purely mechanically by a system of pre-adjustable springs in the winding head.

Through experiments and theoretical considerations to the prevailing

Tension level (pre-tensioning and additional tension during winding, e.g. from its own weight) in the bundle tubes or its development, it is known that the pipe pre-tensioning only accounts for a fraction of the total tension (insofar as it can actually be maintained at the preset level). Even if the applied pipe prestressing force of e.g. 100 N to 300 N could be fully implemented for pipe prestressing, there are currently only minor expansions associated with prestressing that contribute to the bundle cohesion.

The pre-tensioning of the tubes is necessary to ensure that the bundle is held together during the entire winding process. This is especially true in the lower and later also in the upper area of the tube bundle. If the pretension cannot be maintained, the bundle of bundles gradually dissolves after the stirrup-web connections tear and the cohesion is impaired or the ideal shape of the tube bundle cannot be maintained. Furthermore, the tube prestressing ensures the necessary friction within the tube bundle. This is independent of the bracket

Load transfer in axial as well as in tangential direction necessary. Can this friction e.g. are increased by increasing the preload, this contributes to a more uniform bundle behavior (predictability of bundles) and can also partially relieve the stirrups.

Based on this, the present invention is based on the object of improving a method of the type mentioned at the outset so that a larger one

Prestressing of the tubes of the tube bundle can be achieved.

This object is achieved by a method for winding at least one tube onto a core tube of a wound heat exchanger according to claim 1. Advantageous configurations of the method according to the invention are specified in the corresponding subclaims and are described below.

According to claim 1, the inventive method for producing a tube bundle of a wound heat exchanger provides that at least one tube is wound onto the core tube in a helical manner by rotating the core tube around its longitudinal axis, with an instantaneous outer surface of the tube bundle being wound onto the core tube The section of the at least one tube to be wound up is heated by means of a heating device, so that the wound tube receives a defined pretension when it cools, and / or that when the at least one tube is wound up, a section of the at least one tube to be wound onto an instantaneous outer surface of the tube bundle is mechanically Bend the section a curve with a

Obtains a radius of curvature which is smaller than a radius of curvature of the current outer surface of the tube bundle, so that the at least one tube receives a bias.

At the beginning of the process, the said momentary outer surface of the tube bundle is formed by an outer surface of the core tube or by a base body having the core tube, since at the beginning of the winding process a complete tube layer is not yet arranged on the core tube.

The method according to the invention can provide that either a thermal treatment of the pipe section to be wound up takes place or the said mechanical bending of the pipe section that is currently being wound up. However, these two basic procedures can also be combined.

With the method according to the invention, a precisely defined tube bundle designed for the later operating conditions can advantageously be created, in which each tube can receive a significantly higher prestress due to the thermal or mechanical processing.

Due to the springs used so far, e.g. 100 N to 300 N

Pre-tensioning force applied to the pipe during winding. The achievable here

Pre-tensioning is usually not enough to cope with the compressive stresses that arise the load flow in the tube bundle (from the coiled layers). Furthermore, a stiffening of the pipe layers is required to cope with the rising

To be able to compensate the dead weight of the individual layers. By the

thermal method according to the invention for applying the prestress or

Pre-expansion, significantly higher pre-expansion can be achieved through the material-specific thermal expansion coefficient of the pipe material (for material 1.4301 or X5CrNi18-10 approx. 0.000016 / K).

This already applies to a comparatively low heat input and rapid cooling of the tubes to be wound. Even with a maximum permanent temperature increase during winding of 10 K, a pre-expansion of the said pipe material in the range of 0.016% is obtained, which is a significantly higher one

Preload than corresponds to the mechanically applied preload.

According to one embodiment of the method, it is provided that the section of the at least one tube that is currently to be wound is heated to a temperature that is less than or equal to 70 ° C., in particular less than or equal to 65 ° C., in particular less than or equal to 60 °.

According to one embodiment of the invention, it is also preferably provided that the section to be wound up at the moment is heated to at least a temperature which is at least 1 ° C, preferably at least 5 ° C, preferably at least 10 ° C, preferably at least 20 ° C, preferably at least 30 ° C. is above a later cooling temperature to which the section cools, the cooling temperature being in particular room temperature (for example 20 ° C.).

In the method, a section of the at least one tube is therefore preferably continuously heated, which is then wound onto the core tube or the wound body that has already been produced, which later results in the finished tube bundle. The temperature of the pipe section that is currently being wound can thus be set comparatively precisely.

The heating of the at least one tube or of the respective tube to be wound by means of induction is considered to be particularly promising. This consideration is based on the fact that every electrically conductive material is inductively heated can. Another benefit of inductive heating is that it is excellent

Automation and the very precise (especially workpiece-dependent) setting options (e.g. penetration depth of the current, amount of heat, etc.).

Correspondingly, according to one embodiment of the method, it is provided that the heating device has an inductor, the respective section of the at least one tube currently to be wound up being heated by means of the inductor by generating an electrical current in the tube or in the relevant section of the tube (Joule heat ). As an alternative to this, the respective section of the pipe to be wound up at the moment can be heated by means of a laser or by means of hot air or by means of a burner or by means of ultrasound or by means of microwaves.

Furthermore, according to one embodiment of the method, it is provided that the winding of the at least one tube is carried out with the aid of a movable winding head, the winding head being moved along the core tube when winding the at least one tube around the at least one tube in a helical manner on the rotating one Wind up the core tube. According to one embodiment of the method, the heating device can be integrated into the end winding.

If the section of the at least one tube that is currently to be wound is mechanically bent, it can be provided that the above-described mechanical bending of the section is carried out by means of the winding head.

For this purpose, the winding head can have a correspondingly shaped guide through which the at least one tube is forcibly guided during winding, so that the section of the tube that is currently being wound is given a curvature with the said radius of curvature.

Furthermore, according to one embodiment of the method, it is provided that the at least one tube is wound onto the core tube with the interposition of webs extending along the core tube. Of course, several tubes can also be wound onto the core tube using the method according to the invention. For each pipe layer, at least one pipe is wound onto an outside of the core pipe or onto the previous pipe layer, each with spacers in the form of elongated webs in between.

The spacers each extend parallel to the longitudinal axis of the core tube and are preferably arranged equidistant from one another in the circumferential direction of the tube bundle. The subsequent pipe layer is wound onto the pipe layer below and the spacers arranged on it. The respective pipe layer is therefore supported on the pipe layer below via the spacers.

It is also preferably provided that the at least one tube to be wound onto the core tube is initially provided wound on a drum, with the at least one tube being unwound from the drum in sections and wound onto the core tube during said winding onto the core tube. The at least one tube is preferably passed through a straightening device before being wound and in particular before being heated by the heating device or before mechanical bending, which is configured to straighten the at least one tube in sections before winding.

Another aspect of the present invention relates to a device for producing a tube bundle of a wound heat exchanger, in particular for

Implementation of the method according to the invention, wherein the device has a drive for rotating a core tube of the heat exchanger about a longitudinal axis of the core tube, and wherein the device has a heating device which is designed to heat a section of the at least one tube that is on a momentary surface of the tube bundle is to be wound up, and / or wherein the

The device is designed to mechanically bend a section of the at least one tube to be wound onto an instantaneous outer surface of the tube bundle when the at least one tube is being wound, so that the section is given a curvature with a radius of curvature that is smaller than a

Radius of curvature of the current outer surface of the tube bundle. Furthermore, according to one embodiment of the invention, it is provided that the heating device has an inductor for heating the tube to be wound up or the respective section to be wound up.

Alternatively, it can be provided according to one embodiment that the heating device for heating the at least one tube

has a laser, or

is designed to generate hot air, or

has a burner, or

is designed to generate ultrasound, or

is designed to generate microwaves.

Furthermore, according to one embodiment of the invention, it is provided that the device has a movable winding head for guiding the at least one tube when the at least one tube is being wound onto the core tube.

Said heating device can be arranged in the winding head.

Furthermore, the winding head can have a guide which is designed to mechanically bend the section of the at least one tube to be wound onto the current outer surface of the tube bundle when the section is moved along the guide.

Further details and advantages of the invention are to be explained by the following description of the figures of exemplary embodiments on the basis of the figures.

Show it:

Fig. 1 is a fragmentary sectional view of a wound

Heat exchanger;

Fig. 2 is a schematic sectional view of an embodiment of a

Device for winding a tube onto a core tube of a

Heat exchanger; and Fig. 3 is a schematic sectional view of a further device for

Winding a tube onto a core tube of a heat exchanger. FIG. 1 shows an example of a wound heat exchanger 1. This is designed for the indirect heat transfer between a first and at least a second fluid S, S ‘and has a jacket 10 which surrounds a jacket space M for receiving the first fluid S, which e.g. Can be introduced into the jacket space M via an inlet connection 101 on the jacket 10 and via a corresponding one

The outlet connector 102 on the jacket 10 can be withdrawn from the jacket space M again, the first fluid S being a tube bundle 2 of the

Heat exchanger 1 acted upon from above.

The jacket 10 of the heat exchanger 1 extends along a longitudinal axis z, which extends along the vertical in relation to a properly arranged state of the heat exchanger 1. The tube bundle 2 has a plurality of tubes 20 for receiving the at least one second fluid S ‘. Different second fluids S ‘can e.g. are routed in assigned tubes or tube groups of the tube bundle 2, i.e. the tube bundle 2 is divided according to the number of second fluids S ‘to be conveyed. The tubes 20 are helical to a core tube 21 of the

Heat exchanger wound so that a plurality of pipe layers 200, 201, 202 are formed, which are arranged one above the other in a radial direction R that is perpendicular to the longitudinal axis z, the core tube 21 also extending along the longitudinal axis z and coaxially to the jacket 10 is arranged in the shell space M. In relation to the radial direction R, there is an innermost pipe layer 201, which is surrounded in particular by further pipe layers 200 arranged one above the other in the radial direction R, with an outermost pipe layer 202 ultimately surrounding the pipe layers 200, 201 arranged below and an outer side of the tube bundle 2 trains.

Furthermore, the individual pipe layers 200, 201, 202 are preferably fixed to one another via spacers 6 in the form of webs extending along the longitudinal axis z, with several spacers 6 being arranged one above the other in the radial direction R of the tube bundle 2. A constant number of spacers 6 is preferably provided between the adjacent pipe layers 200. Several tubes 20 can each be combined in a tube sheet 104, wherein the second fluid S ′ or several second fluids S ′ can be introduced into those tubes 20 via inlet connections 103 on the jacket 10 and withdrawn from the tubes 20 via outlet connections 105 . Heat can thus be transferred indirectly between the first fluid S and the at least one second fluid S ', these fluids S, S' being able to be passed through the heat exchanger 1, for example, in countercurrent. The jacket 10 and the core tube 21 are in particular designed to be cylindrical, at least in sections, so that the longitudinal axis z forms a cylinder axis of the jacket 10 and the core tube 21 extending concentrically therein. In the shell space M, a preferably hollow-cylindrical Flemd 3 can also be used

be arranged, which surrounds the tube bundle 2 in order to reduce a bypass flow of the first fluid S guided in the shell space M past the tube bundle 2.

The individual tubes 20 are preferably wound onto the core tube 21 using a method shown schematically in FIGS. For this purpose, a device 30 according to the invention is preferably used, which is shown in each case schematically in section in FIGS. FIGS. 2 and 3 show different embodiments of the device 30.

According to FIG. 2, the device 30 can have a drum 32 on which the tube 20 to be wound can be provided. Furthermore, the

Device 30 have a straightening device, not shown here, which is designed to straighten a pipe section unwound from drum 32. The straightened tube section of the tube 20 is then wound onto the core tube 21 by suitably fixing it to the core tube 21 or to a previously wound tube layer and then rotating the core tube 21 around the longitudinal axis z by means of a drive 31.

In this case, a section 20a of the tube 20 to be wound up in each case is wound onto the core tube 21 or onto a momentary outer surface 20b of the

Tube bundle 2 preferably continuously heated with a sausage device 34, wherein the sausage device 34 can be arranged in a winding head 33 of the device 30. The winding head 33 is designed to guide the tube 20 and is moved along the longitudinal axis z of the core tube 21 when the core tube 21 rotates, so that the tube 20 is wound helically onto the core tube 21.

The heating device 34 can for example have an inductor 35 for heating the pipe section 20a, to which a suitable voltage is applied so that the inductor 35 generates an alternating magnetic field that generates corresponding eddy currents in the section 20a of the pipe 20 that heat the section 20a (Joule heat).

The heated section 20a of the tube 20 expands accordingly and, in the expanded state, is wound onto the spacers 6 which are arranged on the previous tube layer (or initially on the surface of the core tube 21).

When it cools down, the heated tube 20 or the heated section 20a, which is now in the at least partially wound-up state, contracts again, which advantageously has a relatively high definition

Pre-tensioning of the pipe is achieved, which can significantly exceed a mechanical pre-tensioning force that can be applied, especially if necessary.

FIG. 3 shows a further embodiment of a device 30 according to the invention or a method according to the invention, with mechanical preprocessing being carried out here instead of a thermal treatment of the at least one tube 20. Here, when the at least one tube 20 is being wound onto the core tube 21, the section 20c of the at least one tube 20 to be continuously wound onto the current outer surface 20b of the tube bundle 2 is mechanically bent, so that the section 20c has a curvature before being wound onto the said surface 20b with a radius of curvature R1 which is smaller than a radius of curvature R2 of the current outer surface 20b of the

Tube bundle 2, so that the at least one tube 20 is pretensioned against the surface 20b or the tube bundle 2. The radius of curvature R2 of the momentary outer surface 20b lies in the cross-sectional plane running perpendicular to the core tube 21 according to FIG. 3 and relates to the

Circumferential curvature of the tube bundle 2. The mechanical bending of the respective section 20c of the pipe 20 to be wound up can take place when the pipe 20 is wound up by means of a correspondingly shaped guide 33a of a winding head 33 of the device 30. When the core tube 21 rotates, the winding head 33 is moved by means of the drive 31 along the longitudinal axis z of the core tube 21, so that the tube 20 is pre-bent and helically wound onto the core tube 21.

Here, too, the device 30 can have a drum 32 (cf., for example, FIG. 2) on which the tube 20 to be wound can be provided. Furthermore, the device 30 can have a straightening device, not shown here, which is designed to straighten a pipe section unwound from the drum 32 prior to pre-bending by means of the guide 33a of the winding head 30.

List of reference symbols

Claims

1 . Process for the production of a tube bundle (2) a wound one

Heat exchanger (1), wherein the at least one tube (20) is wound helically onto a core tube (21) by rotating the core tube (21) about its longitudinal axis (z),

wherein when the at least one tube (20) is being wound up, a section (20a) of the at least one tube (20) to be wound onto a momentary outer surface (20b) of the tube bundle (2) is passed through a

Heating device (34) is heated so that the at least one tube (20) receives a pretensioning when cooling

and or

wherein when the at least one tube (20) is being wound up, a section (20c) of the at least one tube (20) to be wound onto an instantaneous outer surface (20b) of the tube bundle (2) has a curvature with a radius of curvature (20c) by mechanical bending of the section (20c) R1) which is smaller than a radius of curvature (R2) of the instantaneous outer surface (20b) of the tube bundle (2), so that the at least one tube (20) is pretensioned.

2. The method according to claim 1, characterized in that the section (20a) of the at least one tube (20) is heated by means of the heating device (34) to a temperature which is less than or equal to 70 ° C, in particular less than or equal to 65 ° C, in particular less than or equal to 60 °; and / or that the section (20a) to be wound up at the moment is heated to at least a temperature which is at least 1 ° C, preferably at least 5 ° C, preferably at least 10 ° C, preferably at least 20 ° C, preferably at least 30 ° C above a later Cooling temperature is, wherein the cooling temperature is in particular room temperature.

3. The method according to claim 1 or 2, characterized in that the

Heating device (34) has an inductor (35), the section (20a) of the at least one tube (20) being heated by means of the inductor (35) by generating an electric current in the section (20a) of the at least one tube (20) .

4. The method according to any one of claims 1 to 3, characterized in that the heating device (34)

the section (20a) of the at least one tube (20) is heated by means of a laser, or

the section (20a) of the at least one tube (20) is heated by means of hot air, or

the section (20a) of the at least one tube (20) is heated by means of a burner, or

the section (20a) of the at least one tube (20) is heated by means of ultrasound, or

the section (20a) of the at least one tube (20) is heated by means of microwaves.

5. The method according to any one of the preceding claims, characterized

characterized in that the winding of the at least one tube (20) takes place with the aid of a movable winding head (33), the winding head (33) being moved along the core tube (21) when the at least one tube (20) is wound up, around the at least one Wind the tube (20) helically onto the current surface (20b) of the tube bundle (2).

6. The method according to claim 5, characterized in that the heating device (34) is arranged in the winding head (33).

7 The method according to claim 5 or 6, characterized in that the

mechanical bending is carried out by means of the winding head (33).

8. The method according to claim 7, characterized in that the mechanical bending is carried out by a guide (33a) of the winding head (33) on which the at least one tube (20) is guided along during winding.

9. The method according to any one of the preceding claims, characterized

characterized in that the at least one tube (20) is wound onto the core tube (21) with spacers (6) extending along the core tube (21) in between.

10. Device (30) for producing a tube bundle (2) of a wound heat exchanger (1), in particular for performing the method according to one of claims 1 to 9, wherein the device (30) has a drive (31) for rotating a core tube (20 ) has about its longitudinal axis (z), and

- wherein the device (30) has a heating device (34) which is used for

Heating a portion (20a) of the at least one tube (20) is formed, which on a momentary outer surface (20b) of the

The tube bundle (2) is to be wound up,

and or

wherein the device (30) is designed to mechanically bend a section (20c) of the at least one tube (20) to be wound onto an instantaneous outer surface (20b) of the tube bundle (2) when the at least one tube (20) is being wound, so that the section (20c) is given a curvature with a radius of curvature (R1) which is smaller than a radius of curvature (R2) of the current outer surface (20b) of the tube bundle (2).

1 1. Device according to claim 10, characterized in that the

Heating device (34) for heating the section (20a) of the at least one tube (20) has an inductor (35).

12. The device according to claim 10, characterized in that the

Heating device (34) for heating the at least one tube (20)

has a laser or

is designed to generate hot air or

has a burner or

trained to generate ultrasound or

is designed to generate microwaves.

13. Device according to one of claims 10 to 12, characterized in that the device (30) has a movable winding head (33) for guiding the has at least one tube (20) when the at least one tube (20) is wound onto the core tube (21).

14. Device according to claims 10 and 13, characterized in that the heating device (34) is integrated in the winding head (33).

15. Device according to claims 10 and 13, characterized in that the winding head (33) for the mechanical bending of the section (20c) of the at least one tube (20) has a guide (33a) which is shaped so that the section ( 20c) of the at least one tube (20) said

Curvature is obtained when the section (20c) is guided along the guide (33a) when the at least one tube (20) is wound up.