DD300656A5 - heat exchangers - Google Patents

Abstract

A heat exchanger and a method for operating the same are described. The heat exchanger has a substantially cylindrically symmetrical flow space 2, which is traversed by a first fluid in a substantially vertical direction. Within perpendicularly extending tubes flows a second fluid. According to the invention, fittings for increasing the mechanical stability (support plates 12) are provided. In addition, anti-dazzle plates can be installed parallel to the tubes to dampen acoustic vibrations. The distribution of the first fluid can be optimized by a specially designed baffle 10. Fig. 1

Description

For this 3 pages drawings

The invention relates to a heat exchanger with a substantially cylindrical flow space which is delimited by a jacket, with a number of tubes which pass through the flow space in a direction substantially parallel to the cylinder axis and with at least one pair of nozzles facing each other on the cylindrical surface of the shell are arranged and lead into the flow space. Furthermore, the invention is concerned with a method of operating such a heat exchanger, with a use thereof and with an application of the method. Such heat exchangers are used for a variety of applications for cooling or heating liquids and / or gases by indirect heat exchange. In this case, a fluid enters through one of the nozzle in the flow space, there flows around the tubes with a Strömungsrichturig, which is substantially perpendicular to the cylinder axis, and flows through another nozzle back out. Often the flow space is divided into several sections, each with its own pair of filling and drainage. Such a design in which the fluid flows in the flow space in cross-flow to a second fluid, which is passed through the interior of the tubes, offers the advantage that the first fluid experiences only a very small pressure loss during passage through the heat exchanger. This is effected by a relatively direct passage through the flow space, which, however, requires a very open construction without flow-preventing internals in the flow space. This in turn reduces the mechanical stability and rigidity of the device, so that such heat exchangers can be used so far only at relatively low flow velocities in the flow space. Moreover, in such cross-flow heat exchangers and the problem of distribution of the first fluid in the flow space perpendicular to the flow direction has not been solved satisfactorily.

The object of the invention is therefore to improve a heat exchanger of the type mentioned in that its mechanical stability is sufficient for use at higher flow rates. In this case, a favorable Wärmeübortragungsleistung and a good distribution of the first fluid to be ensured in the flow space. This object is achieved by support plates which are installed substantially perpendicular to the cylinder axis in the flow space. These supports cause a much more stable and rigid mechanical construction and reinforcing rigidity of the cylindrical shell around the flow space. The heat exchanger according to the invention can therefore cope flow velocities up to about 10% of the speed of sound in the flow space. In addition to the mechanical stability in the longitudinal direction, problems can also arise in the heat exchanger due to acoustic vibrations, which are built up by standing waves in planes perpendicular to the cylinder axis. According to a further aspect of the invention, to overcome these difficulties, at least one antinoise sheet can be installed, which is arranged substantially in the flow space to the cylinder axis. In general, two parallel Antidröhnbleche be used on both sides of the cylinder axis, which extend over the full length of the flow space. Under certain circumstances, even an odd number and an asymmetrical arrangement of Antidröhnblechen be favorable. In this way, obstacles are installed in each cross-sectional area, which counteract the formation of standing acoustic waves.

To further increase the stability of the heat exchanger and to facilitate the production of the same, it is advantageous if Antidröhnbleche and support plates are integrally connected to each other, for example by welding the contact surfaces. This creates a particularly stable and rigid honeycomb structure within the flow space. However, in this construction a cross-exchange of the fluid in the flow space between different honeycombs is no longer possible, so that a uniform fluid distribution is not readily ensured. In particular, the exchange between the honeycomb divided region and the edge region of the flow space is greatly hindered, so that the heat transfer performance is not optimal, especially in this edge region.

A further development of the invention has a baffle plate which is arranged substantially perpendicular to the connecting line between two pairwise opposing nozzles and continuously over the full length of the flow space parallel to the cylinder axis. It is advantageous if there is a gap between the longitudinal sides of the baffle plate and the jacket. Compared to usually related baffles, which are only mounted on a small surface below the inlet nozzle and therefore represent only a very rough measure for the distribution of the fluid flowing through the inlet nozzle, the baffle invention causes targeted better supply of fluid in the edge regions of the Strömungsraum.Gs ,

Furthermore, it is advantageous if the baffle plate is divided into sections in the direction of the cylinder axis, the different

have relative hole cross-sectional areas. This allows a targeted distribution of guided through the flow space

Fluids are also achieved in the direction of the cylinder axis. It is advantageous if the baffle plate is divided into sections, each having a whole number η of sections

and be bounded on each side either by one end of the flow space or by a plane lying exactly between two pairs of nozzle perpendicular to the cylinder axis. The sockets are preferably arranged so that the sections are equal in size. A heat exchanger can have several sections or only one. In the latter case, only a pair of nozzles are present.

In a favorable embodiment of the invention, in each case a portion of the baffle plate has an even number η of

successive sections P |, i = 1, ..., n, where respectively the sections

Pi and P _n -i ₊₁ , i = 1, ..., n / 2

with respect to their dimensions a "b-, and their relative hole cross-sectional area U are constructed identically.

The part or pieces are therefore symmetrical with respect to their division into sections to the connecting line of the associated Couple of neck. It proves to be advantageous if the number η of the sections Pi within a section is between 2 and 18, and if

for the relative hole cross-sectional areas Lj of the sections P | applies:

Li> L, ₊ "i = 1n / 2-1.

Preferably, η is between 4 and 8.

In a favorable embodiment of the invention, the ratio between the largest and smallest relative hole cross-sectional area L ₁ ZL _n Z ₂ as a function of Verteillänrjö l _v (= distance between the central axis of the filler neck and limiting the corresponding Toilstückes) and the inner radius r of the filler neck is selected, and although preferably according to the relationship

L, = f-VT7 ~ U ₂ .

The factor f is of the order of 1, for example between 0.8 and 1.3. The ratio 1 _v / r is usually in the range of

3; L ₁ ZL _n Z ₂ is generally about 1.5 to 2.0, preferably about 1.7.

Extensive hydrodynamic calculations have shown that with the aid of such a design of the baffle plate a

favorable distribution of gas, which is guided through the flow space and thus a high

Heat transfer performance of the heat exchanger can be achieved. A value range of L _{n / 2} has proven particularly favorable

between 10 and 30% exposed.

According to a further variant of the heat exchanger according to the invention, which extend through the flow space Tubes in a plurality of along the connecting axis of a pair of sockets lined up bundles, wherein the Tubes are interconnected so that the bundle flows through the fluid flowing in the tubes sequentially

become. In this way, in addition - depending on the mode - a DC or countercurrent effect can be achieved.

The invention also relates to a method of operating such a heat exchanger, wherein each pair of nozzles

a filling and a discharge nozzle, wherein in the method, a first fluid through the / the filler neck in the

Introduced flow space and is led out through the / the drain port and a second fluid through the interior

the pipes is passed. The inventive method is characterized in that the second fluid first in the

Pipes of the drain neck nearest bundle is introduced and then successively the tubes of the

flows through in the direction of the inlet port lying bundle. The second fluid is thus to some extent in the

Passed countercurrent to the first Fiuid. In a further development of the method according to the invention, the first fluid is introduced in gaseous form into the flow space

and partially condensed in the heat exchange with the second fluid.

It is convenient to use water as the second fluid in the process and to view it as a cooling or heating medium. Until about 15 years ago, it was customary to use as quench cooler in ethylene plants heat exchanger, although similar

the type according to the invention has a cylindrical flow space and cooling water pipes lying parallel to the cylinder axis, in which, however, the gas to be cooled is passed back and forth several times over the cross section of the flow space.

However, this results in a much higher pressure loss and the process is overall energetically unfavorable. When energy became scarce and expensive, it was forced to use direct contact cooler and the cracked gas through

to cool direct heat exchange with water. Although such systems have a low pressure loss; However, this is bought by high expenditure on equipment. On the one hand, this is due to the fact that the cooling water is circulated and therefore has to be cooled again in a separate heat exchanger. On the other hand, it is necessary that

separate.

The use of the heat exchanger according to the invention as a step cooler for fission gas in an ethylene plant or the Application of the method according to the invention in a process for obtaining ethylene for cooling cracked gas

now combine the advantages of the two types of fission gas coolers known in ethylene plants, namely, on the one hand, moderate equipment costs and thus relatively low capitalists and, on the other hand, very low pressure drop and thus low pressure

Operating cost. Preferably, the cracked gas is passed as the first fluid through the flow space. The invention and further details of the invention are described below with reference to a schematic in the drawings

illustrated embodiment illustrated.

Show here 1 shows a longitudinal section in a vertical plane, 2: a cross section and 3 shows a further longitudinal section in a horizontal plane through a heat exchanger according to the invention.

The jacket 1 of the heat exchanger is designed substantially cylindrically symmetrical about the axis 8. It encloses together with the partitions 3 A and 3 C, the flow space 2. This in turn is divided by a further partition wall 3 B into two subspaces between which no gas exchange is possible. To the subspace arranged on the left in FIG. 1 belongs a first pair 4 of connecting pieces, Ic. It is made up of inlet stub 4 A and outlet stub 4 B. Similarly, on the right side, the sockets 5A and 5B of the pair 5 can be seen.

According to the invention, two support plates 12 are installed in the flow space, the number of which in the exemplary embodiment amounts to a total of 10, ie 5 per subspace. The support plates 12 are supported by a bottom 15. Furthermore, two antidrone sheets 11 are shown in FIG. 2, which extend over the full length of the flow space 2 from the dividing wall 3 A to the dividing wall 3 C (see FIG. 1). Support plates 12, Antidröhnbleche 11 and partitions 3 A, 3 B, 3C are welded together and form a rigid, honeycomb-like structure in which no lateral gas exchange between the honeycomb and no exchange to the volume between Antidröhnblechen 11 and shell 1 is possible.

For this reason, a baffle plate 10 is provided according to the invention, which is arranged below the inlet stub 4A, 5A in a horizontal plane over the full length of the flow space 2. The width b of the baffle plate 10 shown in FIG. 10 is approximately equal to the inner diameter 2 r of the filler neck 4A, 5A. However, b may also be slightly larger or smaller than 2r (see numerical example below). In the transverse direction, the baffle plate 10 is bounded by the two Antidröhnbleche 11 and connected to these cohesively.

By this arrangement, the perforated baffle plate 10 causes a difficult passage of the introduced through the inlet nozzle 4A, 5A fluid in the central part of the flow space 2 and thus a better distribution through the spaces 1414 (see Figure 2) in the direction of the edge volume between Antidröhnblechen 11 and jacket 1. Analogous to the subspaces of the flow space 2, the baffle plate 10 is divided by the partition wall 3 B into two sections. Each of the two sections of the baffle 10 consists of sections P ₁ to P ₆ and P ', to P' _e , as shown in Figure 3. The number η of the sections per section is 6 in the exemplary embodiment. The baffle plate 10 has, in a special version, three different types of perforations, which are distinguished by different relative hole cross-sectional area. By relative hole cross-sectional area is meant the ratio between the opening area of the holes and the total area of the sheet. The different types of punching can be realized by different densities and / or sizes of holes. Preferably, in the embodiment, three different values Li, L ₂ , L ₃ of relative hole cross-sectional areas are used, namely

L ₁ for P ₁ , P ₆ , P ',, Ρ' «, Lj for P ₂ , Pt, P'j, P'6 and L ₃ for P ₃ , P ₄ , P'a, PV

The perforations are chosen so that the relative hole cross-sectional area (L ₃ ) is the smallest and directly at the sections farthest from the inlet ports 4A, 5A, the relative hole cross-sectional area (Li) is greatest, just below the inlet ports 4A, 5A, to a uniform as possible To achieve fluid distribution in the flow space along the cylinder axis. In a heat exchanger designed for purposes of competition, the following numerical values were chosen:

Diameter of the flow space Radius of the opening of the filler neck Distribution length Length of each section Width of the sections

relative hole cross sections

Ratio max. to min. relative hole cross section hole diameter

hole pitch It is manufacturing technology favorable, the length a dor sections Pι to P ₆ and Pi 'to P ₆ ' equal to the distance between two To choose support plates 12. Of course, in terms of distribution, a higher number of sections is different

relative hole cross-sectional areas cheaper; in the hydrodynamic calculations, a value range for the number η of sections per section from 2 to 18, as a practicable compromise between distribution quality and equipment expenditure

preferably 4 to 8 proved.

The tubes which pass through the flow space 2 are not explicitly shown in the drawings. In the longitudinal section of Figure 1 are their straight sections between the baffle plate 10 and the support plate 15. At the ends of the heat exchanger are the Tubes either with one of the sockets 6A, 6B or interconnected, as in the following with reference to FIG 2 closer

is explained.

In the cross-sectional representation, four bundles A ₁₂ to A _{78 are} shown, each of which is divided into two subgroups of 50 to 300,

preferably 120 to 250 tubes and each fill a marked by two crossed lines volume on both sides of a

Antidröhnbleches 11 off. The tubes are connected to each other so that a fluid which is fed via the nozzle 6 A, first parallel to the Pipes of the subgroup Ai flows through and then successively through the tubes of the remaining subgroups and bundles

in the order A ₂ , A ₃ , A », Ag, A ₆ , A ;, Ag and then to the outlet port 6 B is passed.

d. = 1676 mm r = 348 mm iv = 999 mm a = 333 mm b = 666 mm L, 40% L ₂ 30% L ₃ 23% U / U = 1.74 d, = 8mm d ₂ = 8 mm d ₃ = 10mm t, = 12mm tj = 14mm ta = 20 mm

In the method according to the invention, the heat exchanger is operated so that a first fluid - for example, split gas in a Ethylenanlage- in two parallel streams on the inlet nozzle 4 A and 5 A in the flow space 2 and out through the outlet nozzle 4 B, 5 B again led out , as indicated by arrows in Figures 1 and 2. In cross-flow to a second fluid - for example, cooling water is fed through the nozzle 6A, passed through the pipes, not shown, and again taken over the nozzle 6B (arrows 7 in Figure 1).

Claims (17)

1. A heat exchanger having a substantially cylindrical flow space (2) which is delimited by a jacket (1), with a number of tubes passing through the flow space (2) in a direction substantially parallel to the cylinder axis (8) and having at least one A pair (4, 5) of connecting pieces, which are arranged opposite one another on the cylindrical surface of the jacket (1) and lead into the flow space (2), characterized by supporting plates (12) which are substantially perpendicular to the cylinder axis (8) in the flow space (2) are installed. 2. Heat exchanger according to claim!, Characterized by at least one Antidröhnblech (11) which is arranged substantially parallel to the cylinder axis (8) in the flow space (2). 3. Heat exchanger with the features of claims 1 and 2, characterized in that Antidröhnblech (s) (11) and support plate (s) (12) are cohesively connected to each other. 4. Heat exchanger according to one of claims 1 to 3, characterized by a baffle plate (10) which is substantially perpendicular to the connecting line between two pairs of opposing nozzles (4A, 4B, 5 A, 5B) and continuously over the full length of the flow space (2). is arranged parallel to the cylinder axis (8). 5. Heat exchanger according to claim 4, characterized in that between the longitudinal sides (13) of the baffle plate (10) and the jacket (1) is a gap (14). 6. Heat exchanger according to one of claims 4 or 5, characterized in that the baffle plate (10) in the direction of the cylinder axis (8) into sections (P ₁ to P ₆ , ΡΊ to P ' ₆ ) is divided, the different relative hole cross-sectional areas ( L ₁ to L ₆ , U, to L ' _e ), 7. Heat exchanger according to claim 6, characterized in that the baffle plate (10) in sections (20,20 ') is divided, each having an integer number η of sections (P ₁ to P ₆ , ΡΊ to P' ₆ ) and on each side either through one end (3 A, 3 C) of the flow space (2) or through an accurate, between two pairs (4,5) of nozzles (4A, 4B, 5 A, 5 B) perpendicular to the cylinder axis (8) lying Level (3B), be limited. 8. Heat exchanger according to claim 7, characterized in that in each case a portion (20,20 ') of the baffle plate (12) has an even number η of successive sections P ₁ , i = 1, ..., n, wherein in each case the sections P ₁ and P _n _i + i, i = 1, ..., n / 2 with respect to their dimensions ai, b, and their relative hole cross-sectional area Lj are constructed identically. 9. Heat exchanger according to claim 8, characterized in that the number η of the sections Pj (P ₁ to P ₆ , ΡΊ to P ' ₆ ) within a portion (20,20') is between 2 and 18 and that for the relative hole cross-sectional areas Lj sections Pj applies: Li> L _{i + 1} , i = 1n / 2-1 10. Heat exchanger according to claim 9, characterized in that for the maximum relative hole cross-sectional area L ₁ : L ₁ = f * VVr "* L _n / 2, with f: factor, 0,8Sfg1,3 l _v : distribution length (= distance between connection axis of a pair [4,5] of connection piece and limitation of the corresponding one Teilstückos)
r: radius of the opening of the filler neck (4A, 5A) 11. Heat exchanger according to one of claims 1 to 10, characterized in that the tubes in several along the connecting axis of a pair (4,5) of connecting pieces (4A, 4 B, 5A, 5 B) lined up bundles (A ₁ ^ to A ₇ , ₈ ) are combined, wherein the tubes are connected to each other, that the bundles (A ₁ ^ to A ₇ , ₈ ) are flowed through by the flowing fluid in the tubes sequentially. 12. A method of operating a heat exchanger according to claim 11, wherein each pair (4,5) of nozzles consists of a filling (4A, 5A) and a discharge nozzle (4B, 5B), a first fluid through the filler neck (4A, 5A) is introduced into the flow space (2) and out through the / the drain port (4B, 5B) and a second fluid is passed through the inner of the tubes, characterized in that the second fluid first into the tubes of the Ablassstutzen (4B, 5B) closest Bündol (Ai, 2) is introduced and then successively the tubes of the further in the direction of the inlet connection (4A, 5 A) lying frets! {Α _3ι4 to A _7i8 ) flows through. 13. The method according to claim 12, characterized in that the first fluid is introduced in gaseous form into the flow space (2) and partially condensed in the heat exchange with the zweitan fluid. 14. The method according to claim 12 or 13, characterized in that water is used as the second fluid. 15. Use of a heat exchanger according to one of claims 1 to 10 as a step cooler for fission gas in an ethylene plant. 16. Application of the method according to any one of claims 12 to 14 in a process for the recovery of ethylene for cooling cracked gas. 17. Application according to claim 16, characterized in that the first fluid consists of fission gas.