DE29824612U1 - Heat exchanger - Google Patents

Description

EHW Thale EMAIL GmbH

# 6069 E/fr

25.07.2001 - Description

Heat exchanger

The invention relates to a heat exchanger with a first container area for a medium to be cooled or heated, in particular a chemically aggressive medium, wherein a number of tubular lines made of an enamelled metal run in this first container area, the inner cavities of which form a second container area for a second cooling and/or heating medium and which lines lead through openings in a tube sheet out of the first container area and into one or more chambers with the second cooling or heating medium.

Heat exchangers are required for a wide range of applications; heat exchangers for chemically aggressive media, such as acids or gases, represent a particularly demanding special case. The point is that such a medium needs to be cooled or heated, for example during its reaction or storage, and as effectively and quickly as possible. Heat exchangers are naturally ideal for this. The medium, especially water, which usually cools and dissipates reaction heat (or in certain applications also heats it), is led through pipes which are surrounded on the outside by the aggressive chemical medium. The heat exchange takes place through the pipe wall. These pipes must be made of a highly resistant material or protected in some other way against the chemically aggressive medium. Contact between the media must be avoided, as must the chemically aggressive medium diffusing out of the heat exchanger at unintended locations. A particular problem area is the exit of the pipes from the volume area, i.e. the first container area specified above in which the chemically aggressive medium is located.

EHW Thale EMAIL GmbH

# 6069 E/fr

25.07.2001 - Description

In known heat exchangers for this purpose, for example, both the pipes and the corresponding tube sheet through which the pipe is led out are made of tantalum. This is of course very complex, especially in terms of cost.
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Alternatively, enamelled steel pipes are used which are guided through a tube sheet, with the passages being secured with appropriate seals, such as sealing rings. This is both complex and only provides incomplete protection, as these seals are themselves vulnerable and have to be made from a material other than steel, usually plastic.

It would be extremely dangerous if the chemically aggressive media could diffuse through these ducts in any way, as they could then get into the other cooling or heating medium, thus reaching the unprotected inside of the pipes and causing considerable damage there. In addition, corrosion can also occur within the area of the ducts or in the adjoining areas of the chamber. This leads to a significantly shortened service life of the heat exchanger.

It is not possible, as might be obvious in other areas of technology, to weld the steel pipes to the tube sheet in the penetration area. These welds would themselves be exposed to the aggressive medium and could not be re-enamelled or otherwise protected in this area because there is no geometric accessibility for this.

In contrast, one object of the invention is to propose a heat exchanger with an improved design. This object is achieved in a heat exchanger of this type in that the enamelled outer surface of the lines and the inner surfaces of the openings lie on one another in a press fit without seals and without leaks.

EHW Thale EMAIL GmbH

# 6069 E/fr

25.07.2001 - Description

This type of construction solves the problem in a surprising way: a feedthrough in which the enamelled coatings sit directly on top of each other, are leak-proof and press-fitted together, and the opening, which is also seal-free, meets all requirements. There are no longer any components that are exposed to the corrosive medium and this cannot penetrate through either.

Until now, all experts would have considered such a concept impossible; they have never even considered it. This is due in particular to the complicated shapes of the pipes in these heat exchangers, which are bent and cannot be enamelled separately, and due to the geometric conditions, there is practically no way of inserting them in a press fit. Experts also have the problem that enamel cannot be machined with such great precision that a liquid- and gas-tight connection is created.

Contrary to the prejudice of experts, however, this is possible according to the invention.

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EHW Thale EMAIL GmbH

# 6069 E/fr

25.07.2001 - Description

In a process for producing this heat exchanger according to the invention,

- Pipes are manufactured by preparing and enamelling short, straight sections, these short, straight sections are connected and welded via one or more connecting sections and the joints are locally re-enamelled,

or pipes are manufactured by machining complete enamelled U-pipes at the straight ends and connecting them to the openings by press fitting,

the pipes or at least their short straight sections are cryogenically cooled and inserted with their short, straight sections into the openings in the vessel wall,
Heating then causes expansion and thus a press fit of the short straight sections in the openings.

For this purpose, the press fit is preferably created by cryogenic shrinkage. This has the particular advantage that it is possible to join the parts precisely. As has been shown, it is easily possible to pass the standardized helium leak test with such a design.

It is particularly preferred if the tube sheet is also made of enamelled metal, this applies in particular to the inner surfaces of the openings through which the pipes pass.

It is also particularly advantageous to use an enamel layer of only 500 to 600 pm thickness, which is only slightly thicker in the area of the feedthrough, i.e. in the area of the press fit. A very thin enamel layer can reduce the heat transfer coefficient k (W/m ² K) on the pipes, which naturally greatly improves the functionality of a heat exchanger.

EHW Thale EMAIL GmbH

# 6069 E/fr

25.07.2001 - Description

Furthermore, it is particularly preferred if the lines each consist of a pipe section that forms the area inside and adjacent to the passage through the opening, as well as further pipe sections manufactured separately. This makes it possible to manufacture the one relatively short pipe section for the actual passage with high precision and with the utmost precision, also with regard to avoiding angular deviations, which is a great advantage for an accurate press fit.

In particular, it must be taken into account that lines in heat exchangers of the type of interest preferred here have two straight, parallel sections that are intended to pass through two openings in a common tube sheet and that are connected to the openings in the area exactly opposite to the tube sheet inside the vessel by means of a section bent by 180°. In order to pass through the tube sheet, it is therefore necessary to lead this entire element of the line exactly parallel through the sheet so that both outer sides of the line run exactly parallel in the openings in the press fit during cryogenic shrinkage, since even small tilts could lead to problems.

According to the invention, the remaining longer part of the line can then be welded to the short straight sections and the connecting areas can be locally re-enamelled. These longer parts are less critical and only need to be manufactured with normal precision.

It is also possible to standardize the production of heat exchangers. For each heat exchanger, pipes of different lengths are used, which run over each other in a geometrically non-disruptive manner; the curved connecting sections have different lengths, the longer, straight sections can be manufactured using continuous processes, as described in DE 195 03 999 A1, for example, and cut to the required lengths and assembled.

EHW Thale EMAIL GmbH # 6069 E/fr

25.07.2001 - Description

An embodiment of the invention is described in detail below with reference to the drawing. They show:

Figure 1 shows a section through a heat exchanger perpendicular to a wall through which the pipes pass;

Figure 2 is a view, partly broken away, from the chamber to the

Tube sheet and 10

Figure 3 is a schematic representation of an embodiment of a line.

A heat exchanger shown schematically in Figure 1 has a cylindrical container 5 with an outer wall 7 and an inner first container area 10. In the container area 10 there is an aggressive medium that reacts or is stored there and is to be cooled in a defined manner or, if necessary, heated. The medium can be a gas or a liquid; the actual reaction can also take place outside the container, so that the medium is only fed into the container 5 for the purpose of heat exchange. The aggressive medium is fed into the container area 10 through a nozzle 8 and out again through a second nozzle 9.

In addition to the nozzles 8 and 9, a tube sheet 14 is particularly noteworthy. This closes off a side surface of the elongated cylindrical first container area 10 and is detachably connected to the other container walls. However, this connection is highly sealed and closed.

A plurality of openings 15 extend through the base 14. The base 14 is made of an enamelled metal, possibly also of a relatively corrosion-resistant material such as Hastelloy.

EHW Thale EMAIL GmbH

# 6069 E/fr

25.07.2001 - Description

Inside the container area 10 there are a number of tubular lines 20. These lines 20 extend through the tube base 14 or the openings 15 therein and lead to a chamber 25 or 26. This connection forms the second container area for a second medium, which is usually not aggressive and is often water or consists of a high percentage of water. This second medium is used to remove or supply heat. There is therefore as intensive a heat exchange as possible between the two container areas, but no physical contact or even exchange.

The second medium is fed to the chamber 25 via a feed 27. From the chamber 25 it flows into the lines 20 and through the openings 15 in the tube sheet 14. Through the lines 20 it passes over the long straight section (shown upwards in Figure 1) into the top of the bend and again in another long straight section downwards, again through openings 15 in the tube sheet 14 back into the second chamber 26. The second medium then flows out of the chamber 26 via an outlet 28.

The chambers 25 and 26 are separated by a partition wall 29; overall, these two areas together represent a 2-chamber system. The content of the two areas 25 and 26 of the chambers differs in terms of their inherent temperature. Since this is a heat exchanger as a whole, the second medium absorbs (or releases) temperature from the first medium in the container 5 as it flows through the line 20, so that it arrives in the chamber 26 at a higher (or lower) temperature than it had in the exit area of the chamber 25.

The second medium can usually be reused after it has been cooled down or brought back to the desired temperature. Since it is usually ordinary water or a substance with a high water content, working with this medium is relatively uncritical.

EHW Thale EMAIL GmbH

# 6069 E/fr

25.07.2001 - Description

Figure 2 shows a view from the chamber 25, 26 in the direction of the container wall 14. The inlet 27 to the chamber 25 and the outlet 28 from the chamber 26 can be clearly seen in section, as well as the partition wall 29 between the two areas of the chamber. In the section shown in Figure 2 **

The openings 15 are in the partially broken-off section on the right;****■

clearly visible, through which the cables 20 pass. From the cables .,, *.

gen 20 is basically just the inner area of the curve at the top of _t "

Figure 1. J****:

Also shown are the nozzles 8 and 9, which supply the first container area 10 with the first medium or discharge it from it.

The lines 20 are - as shown in Figures 1 and 2 when viewed together - arranged one above the other in an arc shape so that the first container area 10 can be traversed by as large a number of such lines 20 as possible and the function of the heat exchanger can be carried out particularly effectively and with many wall contact areas and thus a large heat exchange surface is achieved with minimal mass use, which results in a high degree of efficiency.

Figure 3 shows one of the lines 20 in detail. First of all, the tube sheet 14 can be seen at the bottom, through which the line 20 passes at two points, namely through the openings 15.

The line itself consists of five sections in the embodiment shown, which makes production particularly practical. First of all, two short, straight sections 31 and 32 are provided, which pass exactly through the openings 15 in the tube sheet 14 and are precisely parallel to one another. These short, straight sections 31, 32 are followed by a long, straight section 33 or 34. These long, straight sections are essentially parallel to one another, although this parallelism is less critical. These long sections can be cut with a suitable

EHW Thale EMAIL GmbH

# 6069 E/fr

25.07.2001 - Description

Process, in particular with a continuous process according to DE 195 03 999 A1 and enamelled. The upper ends of the long, straight sections 33, 34 are connected to each other by a connecting curved section 35. ·**1\

When producing the line 20 as a whole, the two long i****:

straight sections 33, 34 are made and enamelled and then connected to the arch... :

section 35 are connected via two welds 38. This creates

through already the largest part of the entire line 20. Now in a pre- : **":

The alignment machine ensures that the two short, straight, also already enamelled sections 31 and 32 are welded to the two free ends of the long, straight sections 33, 34 in such a way that they are exactly parallel to each other and have a precise distance from each other. This again creates two weld seams 38.

In another alternative, the line 20 is made from a completely enamelled U-pipe. When complete U-pipes are used, the weld seams are completely eliminated.

There may therefore be a relatively slight kink at these connection points of the respective straight sections 31 and 33 or 32 and 34, since the manufacturing tolerances of the long sections can be relatively large and only the precise parallelism of the two short end pieces is important.

Now in this phase, all four weld seams 38 between the five individual sections of the line 20 are re-enamelled. The finished line 20 is now inserted into the openings 15 of the tube sheet 14. For this purpose, the line is cryogenically cooled and thus fits easily into the prepared openings 15 of the tube sheet 14, which in turn are enameled, for example. After heating the line 20, an exact press fit is created.

When using complete U-tubes, the ends are machined directly.

EHW Thale EMAIL GmbH

25.07.2001 - Description

To understand the problem, it should be noted that only one line is shown in Figure 3. In practice, as can be seen in Figures 1 and 2, an enormous number of closely spaced openings are created in the tube sheet 14, into which lines must be inserted so as to cover each other. Enamelling at exactly this point during or after the insertion of the lines 20 is not possible.

EHW Thale EMAIL GmbH # 6069 E/fr 25.07.2001 - Description

List of reference symbols

5 container 7 Wall of 5 8th Support 9 Support 10 first container area 14 Tube sheet 15 Openings in 14 20 Line 25 chamber 26 chamber 27 Supply to 25 28 Exit from 26 29 partition wall 31 short, straight section 32 short, straight section 33 long, straight section 34 long, straight section 35 connecting arch section 38 Welds

· · 4

Claims (8)

1. Heat exchanger with a first container area ( 10 ) for a medium to be cooled or heated, in particular a chemically aggressive medium, wherein in this first container area ( 10 ) a number of tubular lines ( 20 ) consisting of an enamelled metal run, the inner cavities of which form a second container area for a second, cooling and/or heating medium and which lines ( 20 ) lead through openings ( 15 ) in a tube sheet ( 14 ) out of the first container area ( 10 ) and into one or more chambers ( 25 , 26 ) with the second, cooling or heating medium, characterized in that the enamelled outer surfaces of the lines ( 20 ) and the inner surfaces of the openings ( 15 ) lie on one another in a press fit without seals and without leaks. 2. Heat exchanger according to claim 1, characterized in that it is a press fit produced by cryogenic shrinkage. 3. Heat exchanger according to claim 1 or 2, characterized in that each of the lines ( 20 ) leads through one of the openings ( 15 ) into the first container region ( 10 ) and one of the other openings ( 15 ) into the same tube sheet ( 14 ) and out of the container region ( 10 ) again. 4. Heat exchanger according to claim 3, characterized in that each of the lines ( 20 ) consists of at least two parallel, non-bent pipe sections ( 31 , 32 , 33 , 34 ) and a third curved section ( 35 ) which performs a bend of 180° and connects the non-bent pipe sections. 5. Heat exchanger according to one of the preceding claims, characterized in that the lines ( 20 ) have at least one relatively short, straight pipe section ( 31 ) in the region of the passage through the openings ( 15 ) of the tube sheet ( 14 ) and a further pipe section ( 33 ) adjoining this relatively short pipe section ( 31 ) and connected to this pipe section by welding, wherein the connection region is subsequently locally re-enamelled. 6. Heat exchanger according to claim 4 and 5, characterized in that the lines ( 20 ) each have two relatively short, straight pipe sections ( 31 , 32 ) in the area of the passage through two openings ( 15 ) of the tube sheet ( 14 ) and respectively adjoining long, straight pipe sections ( 33 , 34 ) connected to the short, straight pipe sections ( 31 , 32 ) by welding, and a fifth curved section ( 35 ) which makes a bend of 180° and connects the long, straight pipe sections ( 33 , 34 ), the four connection areas then being locally re-enamelled. 7. Heat exchanger according to one of the preceding claims, characterized in that the enamel layer on the lines ( 20 ) has a thickness of only 500 to 600 µm outside the area in or adjacent to the openings ( 15 ). 8. Heat exchanger according to one of the preceding claims, characterized in that the tube sheet ( 14 ) also consists of enamelled metal, in particular in the inner surfaces of the openings ( 15 ).