EP2803929B1 - Heat exchanger with heat exchange hoses of plastic material - Google Patents

Description

The invention relates to a heat exchanger having the features in the preamble of patent claim 1.

From the fluid mechanics it is known that cylindrical bodies are vibrated by the formation of counter-rotating vortices in such a way that the bodies themselves begin to oscillate. In particularly critical situations, the separation frequency of the vertebrae can also fall within the range of the natural vibration or the natural frequency of the body. The larger the free-swinging length of tubes, that is, the larger the heat exchangers are, the more likely the problem of vibrational excitation to occur. Particularly large heat exchangers are used, for example, in flue gas desulphurization plants of power plants. Since the aggressive flue gases can attack the heat exchanger tubes, they consist of a corrosion-resistant material, in particular of a corrosion-resistant plastic such. Example, a fluoroplastic, in particular perfluoroalkoxylalkane (PFA) or modified polytetrafluoroethylene (mod. PTFE), which is why plastic hoses. Since this material has a lower strength and rigidity than steel, it also tends to vibrate. In addition, the tubes must be freed from attachments from time to time. This is done by means of water. In order to improve the cleaning result and to prevent the transfer of cleaning water into adjacent tube bundles, the heat exchanger is equipped in the region of side suspensions with side wall films.

Due to the aligned arrangement of the heat exchanger tubes in combination with the flue gas channel dimensions vibrations in the heat exchanger can occur. This is often expressed by humming or roaring, which is unpleasant for the human organism. In addition, it is possible that the mechanical vibrations on adjacent trades such. B. be transferred to housing or work platforms. Depending on the intensity of the vibrations, damage to the components can also occur. The vibrations occur through the formation of Kármán vortex streets. The installation of partition walls (anti-sound boards or acoustic foils) disturbs the formation of Kármán vortex streets. The vibrations are thereby shifted in frequency ranges outside the natural frequency of the heat exchanger tubes. The partitions are installed between two adjacent rows of tubes. The partitions must also, as the tubing consist of a corrosion and heat resistant material. For this reason, a suitable plastic is usually used as a construction material. With a small hose distance, thicker foils (1.5 mm) are used for the partitions. At z. B. 12 mm distance between two adjacent heat exchanger tubes and a film arranged therebetween even the slightest deformation of the film to a contact between the film and the heat exchanger tube. Contact between the hoses and the foils should be avoided at all costs, because the dusty atmosphere in combination with the rubbing contact on the foils leads to abrasion on the surface Heat exchanger hose and leads to the acoustic films. The abrasions on the heat exchanger hose lead in the long term to a failure of the heat exchanger.

The invention has for its object to show a heat exchanger with arranged in the flow direction of the gas stream film elements, which is improved in terms of stiffness of the film, so that the friction between the heat exchanger tubes and the films is reduced or avoided.

This object is achieved with a heat exchanger having the features of patent claim 1.

Advantageous developments of the invention are the subject of the dependent claims.

The heat exchanger according to the invention comprises a plurality of vertically extending heat exchanger hoses made of plastic, which are arranged parallel to each other in rows and are preferably positionally oriented in several planes by holding elements at a distance. The heat exchanger hoses are intended to be flowed across by a gas stream. It is z. B. to a heat exchanger of a flue gas desulfurization. At least one film element, in particular as a sidewall film element, extends in the flow direction of the gas stream. It is arranged in the height range between two mutually spaced retaining elements. The film element is oriented by stiffening means. These stiffening means enforce the retaining elements in the same manner as the heat exchanger hoses.

It has been recognized in the context of the invention that the low inherent rigidity of the film elements is significantly responsible for the abrasive contact between the heat exchanger tubes and the film element and contributes significantly to the destruction of the heat exchanger tubes. Theoretically, it would be possible to use thicker-walled and therefore more rigid film elements of the same type. However, that would significantly increase the material input and effort. On the other hand, the use of particularly resistant and rigid materials would also lead to the destruction of the heat exchanger tubes when they come into contact with the heat exchanger tubes due to differences in hardness, surface structures, etc. For this reason, the foil elements with Provided stiffening, which enforce the holding elements. These film elements may be sidewall films and / or acoustic films.

This may mean, on the one hand, that the holding elements, which are placed in a grid-like arrangement within the tube bundle, serve exclusively for fixing the stiffening means. The stiffening means in this case are struts which extend between successive holding elements.

However, the preferred variant is that the stiffening means are formed by the heat exchanger tubes themselves.

In both variants, the distance of the film element to the adjacent heat exchanger tubes is also kept under high thermal stress. At a center distance of z. B. 24 mm between two adjacent rows of heat exchanger tubes, the film element is now incorporated into the pipe division. The number of stiffeners determines the maximum deformation of the film transverse to the gas inflow. As a result, the risk of contact between the film element and the heat exchanger tubes in an adjacent row is reduced or avoided.

In addition, it should be noted that in large-scale systems, a plurality of heat exchanger tubes is connected in parallel. For example, per tube bundle 1,800 heat exchanger tubes may be provided, which are arranged in individual rows next to / behind each other. By a film element, a holding element for the heat exchanger hoses would be used to accommodate the film, so that about 50 heat exchanger hoses would have to be omitted by the stiffening means in the form of struts. Although this reduces the performance of the heat exchanger slightly, but the advantage is a significantly improved vibration damping and durability of the adjacent heat exchanger tubes, so that the disadvantage of reduced power is more than compensated.

The heat exchanger performance is reduced even less when the stiffener is formed by the heat exchanger tubes themselves. In this case, the heat exchanger hoses stay in place, but do not participate in the heat exchange.

The number can be slightly reduced. Although the film element which is in direct contact with the heat exchanger tubes inhibits the free flow of the affected heat exchanger tubes and reduces the heat exchange to a certain extent on at least one side, this effect results in even lower losses than in the case of bracing means which are designed as separate struts.

The stiffening means in the form of struts are preferably designed so that they can be easily fixed to the holding elements. The holding elements have guide elements in the form of openings for passing through the heat exchanger tubes. For this reason, the struts are cylindrical. They reach through these openings and have a shell. The sheath is preferably made of the same material as the heat exchanger hoses. In a first preferred embodiment, the struts have inside a support profile or reinforced by fillers. The support profile should have a higher rigidity than the sheathing. The sheathing rather serves to protect the support profile from corrosive influences of the gas flow. The support profile may be a non-metallic or a metallic insert, in particular a wire. The wire is surrounded by the sheath made of plastic, in particular of fluoroplastic. The support profile has the function to auszusteifen the casing from the inside, especially if this has a relatively small wall thickness. On the other hand, the support profile should also not be too heavy. Therefore come as a support profile also plastics, in particular glass fiber reinforced plastics in question. Support profiles of non-ferrous metals, such as Aluminum, are also suitable because of the lower weight.

In an alternative embodiment, the stiffening means in the form of struts comprise a casing, wherein within the casing no substantially rigid support profile is arranged, but a filler. The filler consists of a flowable or pourable mass. This filler does not have to completely fill the sheath. With the filler, it depends largely on its weight. That is, it should have such a high weight that the flexible sheath is stretched and due to the stretch of the sheath a stiffener is effected. In this approach, the filler can be selected substantially solely by its specific gravity. It preferably has a greater specific gravity than the sheath itself. In particular, the mass of the filler is at least as large as the mass of the sheath surrounding it. Particularly inexpensive are mineral fillers, such as sand. Of course, other suitable high density materials, such as metals, may be considered. The jacket does not necessarily have to be completely filled with the filler. For example, a filling height of one-third of the total length of the sheath may be sufficient to stretch the sheath and provide sufficient rigidity of the stiffening means. Preferably, the weight of the filler is one to two times the weight of the surrounding shell.

The ends of the casing may additionally be closed. The closed ends can also serve to fix the casing and thus the struts. For this purpose, the closed ends can be enlarged so far in diameter that the ends do not slip through the holding elements. Since it is heat exchanger tubes made of plastic in a hanging arrangement, that is essentially in a vertical orientation, the individual struts hang as it were on the upper side holding elements and are prevented by the ends of the jacket from slipping through the holding elements.

While the connection between the struts and the retaining elements takes place in a form-fitting manner, the film element can in particular be connected in a materially bonded manner to the stiffening means. It may in particular be welded to the stiffening means. The welding of fluoroplastics is especially possible with modified PTFE materials, such as TFM. But the fluoroplastics MFA and PFA can be connected by welding technology. The welding of the film element takes place either in the upper region, so that thermal expansion downwards is possible, or alternatively in the middle region between two holding elements. The central area is defined as the area ranging from 40% to 60% of the vertical distance between two holding elements.

In the context of the invention, of course, also suspensions of the film elements by hooks or clamps and similar components on the top holder assembly are possible, which are either intended to clamp directly the film element, or appropriate recordings for the incorporation of holding elements, such as hooks or clips , exhibit.

The film elements according to the invention can be arranged several times in each plane, depending on the vibration conditions of the heat exchanger. A plane refers to the vertical area between two superimposed holding elements.

The heat exchanger tubes can be arranged on both sides of the film elements, so that the film elements are in a sense located in the central region of the heat exchanger. It is also conceivable, however, an arrangement in which the heat exchanger tubes are arranged only on one side of a film element. This is not necessarily a peripheral arrangement, because it is possible to build a plurality of such heat exchanger parallel to each other, so that the individual heat exchanger with its heat exchanger tubes is indeed only arranged on one side of the film element, but on the other hand immediately adjoin the heat exchanger hoses adjacent heat exchanger , The foil elements can therefore also have the function of delimiting individual regions of the tube bundle of the heat exchanger from other regions of the same heat exchanger or of an adjacent heat exchanger.

Figur 1

in perspektivischer Ansicht einen Teilbereich eines Wärmetauschers in einer ersten Ausführungsform;

Figur 2

in perspektivischer Ansicht einen Teilbereich eines Wärmetauschers in einer zweiten Ausführungsform;

Figur 3

eine perspektivische Ansicht eines Wärmetauschers in einer dritten Ausführungsform;

Figur 4

in vergrößerter Darstellung eine Aussteifungselement im Teilschnitt;

Figur 5

eine Seitenansicht eines Folienelements und

Figur 6

eine weitere perspektivische Ansicht eines Wärmetauschers in einer weiteren Ausführungsform.

The invention will be explained in more detail with reference to an embodiment shown in the drawings. It shows:

FIG. 1

in perspective view a portion of a heat exchanger in a first embodiment;

FIG. 2

in perspective view a portion of a heat exchanger in a second embodiment;

FIG. 3

a perspective view of a heat exchanger in a third embodiment;

FIG. 4

in an enlarged view a stiffening element in partial section;

FIG. 5

a side view of a film element and

FIG. 6

a further perspective view of a heat exchanger in another embodiment.

FIG. 1 shows a perspective view of a portion of a heat exchanger 1. The heat exchanger 1 is, for example, a flue gas heat exchanger. The heat exchanger 1 has, for example, a width of 2 m and a height of 12 m. Several of these heat exchangers 1 can be arranged next to one another in modular construction, so that overall widths of, for example, 10 m result. Heat exchanger 1, the z. B. used in flue gas desulphurisation plants of power plants are exposed to strong corrosive influences. The heat exchanger tubes 2 are therefore made of plastic. Preferably, it is a fluoroplastic, in particular PTFE, MFA, PFA or TFM. The plastic has a reduced rigidity due to the increased operating temperatures. In addition, the material is relatively expensive. Therefore, not too large wall thicknesses should ultimately be installed to improve the heat transfer. For this reason, the heat exchanger tubes 2 are guided by holding elements 3. The holding elements 3 are preferably also made of plastic and are arranged in several height levels. In one possible embodiment, the center distance between two holding elements is 24 mm. The holding elements 3 extend horizontally in the flow direction S of the gas flow G. They are attached to support tubes 4 and support profiles 5 which extend transversely to the flow direction S. For reasons of clarity, only a smaller number of retaining elements 3 and the heat exchanger tubes 2 has been shown. In the practical embodiment, the holding elements 3 extend in substantially greater numbers on both sides of the illustrated heat exchanger tubes 2. Also, many of the support tubes 4 and carrier profiles 5 are arranged one above the other, for example, in vertical intervals of 50 cm to 60 cm. In the context of the invention is spoken by several levels.

According to the invention, at least one film element 6 is arranged in at least one plane, preferably all planes. The film element 6 preferably also consists of a fluoroplastic. It has a thickness of preferably 1 mm to 3 mm and dimensions of about 500 mm in height and at least 1,000 mm in length. The film element 6 extends in the flow direction S.

The special feature of the film element 6 is that it is penetrated by stiffening means 7. The stiffening means 7 extend vertically in the image plane. The number of stiffening means 7 depends essentially on the extent of the film element 6. The lateral extent of the film element 6 must be limited in such a way that contact with the adjacent heat exchanger tubes 2 is safely excluded. Specifically, in this embodiment, the stiffening means 7 are formed by the heat exchanger tubes 2. This means that the stiffening means 7 themselves extend through the holding elements 3, by the same guide elements in the form of openings, which are also provided for the heat exchanger tubes 2. The openings in the holding elements 3, which are actually provided for receiving the heat exchanger tubes 2, thus serve simultaneously for fixing the stiffening means. 7

The connection between the stiffening means 7 and the film element 6 via pockets 8 in the film elements 6. The pockets 8 are formed by two mutually parallel slots 9, 10. These slots 9, 10 extend in the flow direction S in this embodiment. The length of the slots 9, 10 is selected so that the film element 6 can be issued in opposite directions, so that the heat exchanger tube 2 in its function as a stiffening means 7 through the openings in Area of the slots 9, 10 can be performed. As a result, the film element 6 surrounds the stiffening means 7 on both sides. FIG. 1 shows that each stiffening means 7 passes through a plurality of successive pockets 8 in the vertical direction. Out FIG. 1 Furthermore, it can be seen that, in addition to the pockets 8 penetrated by the illustrated heat exchanger tubes 2, additional pockets 8 are additionally provided in the upper region of the film element 6 which are not yet occupied by stiffening means 7 are. These pockets 8 are used to hold other types of stiffening means 7, as in the FIGS. 2 to 4 be explained. The film element 6 is therefore suitable for receiving different stiffening means 7.

FIG. 2 shows a further embodiment of a heat exchanger 1. It will be at FIG. 2 the too FIG. 1 introduced reference numerals used as far as identical or substantially identical components are designated.

FIG. 2 again shows a heat exchanger 1, which differs from the design of the FIG. 1 characterized in that the stiffening means 7a are configured differently. These are not heat exchanger tubes 2, but separate stiffening means 7a in the form of struts. These stiffening means 7a do not have the function to participate in the heat exchange, but only the function to auszusteifen the Fol'ienelement 6. But the stiffening elements 7a enforce also, in the same way as in FIG. 1 the heat exchanger tubes 2, the openings in the holding elements 3 in the vertical direction. The outer dimensions of the stiffening means 7a are identical except for the length. From the sectional view, however, it can be seen that the stiffening means 7a has a closed end 11. Unlike the embodiment of the FIG. 1 Where the heat exchanger tubes 2 continue to extend upward in the image plane, the stiffening means 7a end the FIG. 2 at the position shown. They enforce only one film element 6 completely. In the embodiment of the FIG. 1 For example, a single heat exchanger hose 2 can pass through a plurality of film elements 6 in different planes.

The stiffening means 7a of FIG. 2 in the form of a strut has on the outside a tubular sheath 12. The sheath 12 surrounds an inside support profile 13. The support profile 13 may be a wire or a rod. The support profile 13 is in particular metallic and can be protected from corrosive gases on all sides by the outer casing 12. The sheath 12 is preferably made of the same material as the heat exchanger tubes 1, in particular of a fluoroplastic. It is preferably a weldable fluoroplastic. In which Embodiment of FIG. 2 the end 11 of the casing 12 is closed by a plug 15.

The embodiment of FIG. 3 shows an alternative in which the end 11 is flattened.

FIG. 4 shows this embodiment in an enlarged view. The clipping of the upper end 11 has the advantage that the end 11 is widened. The diameter is larger than the diameter of the opening 12 penetrated by the sheath 12 in the holding elements 3, so that the stiffening means 7a can not slip through the holding element 3. The lower end 14 is closed by a plug 15.

FIG. 3 shows how the lower ends 14 engage in pockets 8 of the film element 6. Below the pocket 8 there is a further slot 16 in the flow direction S of the gas G. As a result, the film element 6 can issue laterally transversely to the flow direction up to the slot 16 and conform to the tubular stiffening means 7a.

FIG. 5 shows a possible embodiment of a film element 6 in a side view. In the upper area are recesses for the support tube 4 and the support section 5, as shown in the FIGS. 1 and 2 is shown. An essential feature of the film element 6 are the pockets 8, several of which are arranged successively in the vertical direction. In this embodiment, there are four pockets 8 per stiffening means 7. In the upper area, a further pocket 8 is additionally provided in each case. This pocket 8 is offset from the former pockets 8. It serves to receive the lower ends 11 of stiffening means, which hold another film element 6 in an overlying plane.

FIG. 6 Finally, a variant showing a combination of the embodiments of FIGS. 1 and 2 represents. In the front image plane, a fixation of film elements 6a by means of stiffening means 7a is provided. The stiffening means 7a are configured as struts which extend only between two successive holding elements 3. As described above, enforce the Stiffening means 7a actually provided for the heat exchanger tubes 2 openings in the holding elements 3. The stiffening means 7a terminate shortly above or just below the respective holding elements 3, so that the respective limited by the holding elements 3 level is completely penetrated and held the film element 6a and stiffened becomes.

In the overlying and underlying film elements 6a additional pockets 8 are formed for this purpose at the edge, which serve to receive the ends 11 of the holding elements 3. This variant corresponds essentially to the embodiment of FIG. 2 ,

In the image plane behind is located on the same heat exchanger 1, the variant of FIG. 1 , That is, the stiffening means 7 are not separate struts, but are formed by the heat exchanger tubes 2 themselves. The heat exchanger tubes 2 in turn extend through the pockets 8. It is therefore possible within the scope of the invention to combine different stiffening means 7, 7a in a heat exchanger with one another.

The two variants have in common that the film element 6 is arranged substantially in the predetermined by the holding elements 3 level for the heat exchanger tubes 2 and stiffening means 7, 7a. By welding the film elements 6, 6a with the stiffening means 7, 7a, in particular in the central region between two holding elements 3, that is in a range corresponding to about 40% to 60% of the distance between two holding elements 3, it can be achieved that the film element 6, 6a upwards and downwards, that is evenly, expands and thus stresses within the film element 6, 6a are avoided. The number of stiffening means 7, 7a limits the lateral deflection of the film elements 6, 6a by thermal expansion.

FIG. 6 shows, moreover, that the holding elements 3 can be arranged on both sides of the film element 6a or the heat exchanger tubes 2 in the holding elements 3 can accordingly run on both sides of the film element 6a. Also conceivable is a configuration in which the Heat exchanger hoses 2 are arranged only on one side of the film element 6, as for example in the FIGS. 1 and 2 can be seen.

Reference numerals:

1 -

heat exchangers

2 -

heat exchanger tube

3 -

retaining element

4 -

support tube

5 -

support section

6 -

film element

6a -

film element

7 -

stiffening

7a -

stiffening

8th -

bag

9 -

slot

10 -

slot

11 -

The End

12 -

jacket

13 -

support profile

14 -

The End

15 -

Plug

16 -

slot

G -

gas flow

S -

flow direction

Claims (15)

1. Heat exchanger comprising a plurality of vertically-extending heat exchanger tubes (2) made of plastic, which are arranged in parallel in rows and are position-oriented by retaining elements (3) at a distance from one another, wherein the heat exchanger tubes (2) are arranged in order to be flowed over transversely by a gas stream (G), and wherein there is at least one foil element (6, 6a) in the flow direction (S) of the gas stream (G), which is arranged at the height region between two retaining elements (3) spaced apart, characterised in that reinforcement means (7, 7a) orients at least one foil element (6, 6a), wherein the reinforcement means (7, 7a) reinforce the retaining elements (3).
2. Heat exchanger according to claim 1, characterised in that the reinforcement means (7) are formed from the heat exchanger tubes (2).
3. Heat exchanger according to claim 1, characterised in that the reinforcement means (7a) are constructed as struts, which extend between successive retaining elements (3).
4. Heat exchanger according to claim 3, characterised in that the reinforcement means in the form of struts include a casing (12), wherein a support profile (13) is arranged in the casing (12).
5. Heat exchanger according to one of the claims 1 to 3, characterised in that the reinforcement means in the form of struts include a casing (12), wherein the space surrounded by the casing (12) at least partially encloses a filler.
6. Heat exchanger according to claim 5, characterised in that the filler has a higher specific weight than the casing.
7. Heat exchanger according to claim 6, characterised in that the filler comprises a mineral material and/or a metal.
8. Heat exchanger according to one of the claims 5 to 7, characterised in that the mass of the filler is at least equal to the mass of the casing.
9. Heat exchanger according to one of the claims 4 to 8, characterised in that the casing (12) is made of the same material as the heat-exchanger tubes (2).
10. Heat exchanger according to any one of the claims 4 to 9, characterised in that the ends (11) of the casing (12) are sealed.
11. Heat exchanger tube according to claim 10, characterised in that the sealed ends (11) are so far enlarged in diameter that the ends (11) do not slide through the retaining elements (3).
12. Heat exchanger according to one of the claims 1 to 11, characterised in that the foil element (6) is firmly bonded with the reinforcement means (7, 7a).
13. Heat exchanger according to claim 12, characterised in that the foil element (6, 6a) is firmly bonded with the reinforcement means (7, 7a) in a range from 40% to 60% of the distance between two retaining elements (3).
14. Heat exchanger according to one of the claims 1 to 13, characterised in that the heat exchanger tubes (2) are arranged on both sides of the foil elements (6, 6a).
15. Heat exchanger according to one of the claims 1 to 14, characterised in that the heat exchanger tubes (2) are arranged on only one side of a foil element (6, 6a).

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