DE3913579A1 - HEAT EXCHANGER - Google Patents

Description

The invention relates to a heat exchanger with an im essential cylindrical flow space through a Sheath is limited, with a number of tubes that the Flow space in substantially parallel to the cylinder axis Pull through the direction and with at least one pair of connecting pieces, the opposite each other on the cylindrical surface of the shell are arranged and lead into the flow space. Further dealt with the invention with a method for operating a Such a heat exchanger, with a use of the same 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 used by indirect heat exchange. In doing so, a fluid enters through one of the spigots in the flow room, lapped there the tubes with a flow direction that is substantially perpendicular to the cylinder axis, and flows through a back out again. Often the flow space is in several sections, each with its own pair of Split filling and drainage pipe. Such a design, in the fluid in the flow space in cross-flow to a second Fluid passing through the interior of the tubes flows,  offers the advantage that the first fluid only a very small Pressure loss when passing through the heat exchanger undergoes. This is done through a relatively direct passage through the Flow space causes, however, a fairly open construction without flow-preventing internals in the flow space presupposes.

This in turn reduces the mechanical stability and Rigidity of the device, so far that such heat exchanger only at relatively low flow velocities in the Flow space can be used. Besides, with such Crossflow heat exchangers also the problem of distribution of first fluid in the flow space perpendicular to the flow direction so far not satisfactorily solved.

The object of the invention is now, a heat exchanger of to improve the type mentioned in that his mechanical stability also for use at higher Flow rates sufficient. It should be a cheap Heat transfer performance and good distribution of the first Be ensured fluids in the flow space.

This object is achieved by supporting plates, which are substantially are installed perpendicular to the cylinder axis in the flow space. These supports cause a much more stable and rigid mechanical construction and enhance the rigidity of the cylindrical shell around the flow space. The erfindungsge Permitted heat exchanger can therefore flow rates up to about 10% of the speed of sound in the flow space handle.

In addition to the mechanical stability in the longitudinal direction can at the heat exchanger also problems due to acoustic vibrations arising due to standing waves in planes perpendicular to Cylinder axis are constructed. According to another aspect The invention can overcome these difficulties at least one anti - drumming sheet be installed in the  essentially parallel to the cylinder axis in the flow space is arranged. In general, two parallel Antidröhnbleche used on both sides of the cylinder axis, the over the full length of the flow space. Under Circumstances can also be an odd number and one unbalanced Arrangement of Antidröhnblechen be favorable. In this way In each cross-sectional area obstacles are built in, which one Counteract formation of standing acoustic waves.

To further increase the stability of the heat exchanger and the Facilitating the production of the same it is favorable if Antidröhnbleche and support plates cohesively with each other are connected, 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 transverse exchange of the fluid no longer in the flow space between different honeycombs possible, so that a uniform fluid distribution not without further is guaranteed. In particular, the exchange between the honeycomb divided area and the edge area of the Flow space is severely hampered, so that the Heat transfer performance especially in this edge area not optimal.

A development of the invention has a baffle plate, the substantially perpendicular to the connecting line between two in pairs opposite nozzles and continuously over the full length of the flow space parallel to the cylinder axis is arranged. It is favorable, if between the Long sides of the baffle plate and the jacket a gap lies.

Compared to commonly related baffles, which only on a small area below the Eintrittsstutzens be attached and therefore only a very  rough measure for the distribution of the through the inlet nozzle represent flowing fluid causes the inventive Baffle targeted a better supply of fluid in the Edge regions of the flow space.

Furthermore, it is advantageous if the baffle plate in the direction of Cylinder axis is divided into sections, the different have relative hole cross-sectional areas. This can be a targeted distribution of the guided through the flow space fluid can also be achieved in the direction of the cylinder axis.

It is advantageous if the baffle plate is divided into sections, each having a whole number n of sections and are limited on each side either by one end of the flow space or by a plane lying exactly between two pairs of nozzles perpendicular to the cylinder axis. The nozzles are preferably arranged so that the sections are the same size. A heat exchanger can have several sections or only one. In the latter case, only a pair of nozzles is present.

In a favorable development of the invention, in each case one section of the baffle plate has an even number n of successive sections P _i , i = 1,. , ., n up, taking each sections

P _i and P _{ni +1} , i = 1 _,. , ., n / 2

with respect to their dimensions a _i , b _i and their relative hole cross-sectional area L _{i are constructed} identically.

The part or pieces are therefore in terms of their distribution in sections symmetrical to the connecting line of the associated Couple of neck.  

It proves to be favorable if the number n of the sections P _i within a section is between 2 and 18 and if the following applies for the relative hole cross-sectional areas L _{i of} the sections P _i :

L _i < L _{i +1} , i = 1 _,. , ., n / 2-1.

Preferably, n 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 / L _{n / 2 is selected} as a function of the distribution length l _v (= distance between the center axis of the filler neck and the boundary of the corresponding section) and the inner radius r of the filler neck, and preferably according to the relationship

The factor f is on the order of 1, approximately between 0.8 and 1.3. The ratio l _v / r is usually in the range of 3; L ₁ / L _{n / 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} between 10 and 30% has proved to be particularly favorable.

According to a further variant of the heat exchanger according to the invention, the tubes extending through the flow space are combined into a plurality of bundles lined up along the connecting axis of a pair of nozzles, the tubes being connected to one another such that the bundles are flowed through successively by the fluid flowing in the tubes. In this way, in addition - depending on the mode - a DC or countercurrent effect can be achieved.

The invention also relates to a method for operating a Such heat exchanger, in which each pair of nozzles from a Einfüll- and a drain pipe is made, wherein in the process a first fluid through the / the filler neck in the Introduced flow space and through the / the drain pipe again is led out and a second fluid through the interior of the Pipes is passed. The method according to the invention is characterized characterized in that the second fluid first into the tubes of the the drain neck nearest bundle is introduced and then successively the tubes in the direction of Inlet neck lying stream through bundles. The second fluid is thus to some extent in countercurrent to the first fluid guided.

In a further development of the method according to the invention the first fluid is introduced into the flow space in gaseous form and in the heat exchange with the second fluid partially condensed.

It is convenient to use water as the second fluid in the process use and use as a cooling or heating medium.

Until about 15 years ago, it was customary as a fission gas cooler in Ethylene plants to use heat exchangers, 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 several times over the Cross-section of the flow space is reciprocated.

However, this results in a much higher pressure loss and The process is overall energetically unfavorable.  

When energy became scarce and expensive, we were forced to Direct contact cooler to use and the cracked gas by direct Cool heat exchange with water. Although such systems have a low pressure loss; this is however due to high equipment costs bought. This is part of it justified that the cooling water are recycled and therefore cooled again in a separate heat exchanger must become. On the other hand, it is necessary that from the Direct contact cooler removed water and condensed out to separate heavy hydrocarbons in a separator.

The use of the heat exchanger according to the invention as Step cooler for fission gas in an ethylene plant or the Application of the method according to the invention in a method to recover ethylene for cooling cracked gas now the advantages of the two types known in ethylene plants of split gas coolers, namely on the one hand moderate apparatus Effort and thus relatively low capital costs and on the other hand very low pressure drop and therefore low operating costs. Preferably, the cracked gas is the first fluid through the Flow space led.

The invention and further details of the invention are in The following with reference to a in the drawings schematically illustrated embodiment illustrated.

Hereby show:

Fig. 1 a longitudinal section in a vertical plane,

Fig. 2 is a cross section and

Fig. 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 the flow space 2 together with the partitions 3 A and 3 C. This in turn is divided by a further partition wall 3 B into two subspaces, between which no gas exchange is possible. To the left are arranged in Fig. 1 partial space has a first pair of nozzles 4, which is formed from inlet nozzle 4 A and 4 B Ausstrittsstutzen. Similarly, on the right side of the nozzle 5 A and 5 B 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 Antidröhnbleche 11 are shown in Fig. 2, which extend over the full length of the flow space 2 of the partition wall 3 A to partition 3 C (see Fig. 1). Support plates 12 , Antidröhnbleche 11 and partitions 3 A , 3 B , 3 C 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 1 shell is possible.

For this reason, a baffle plate 10 is provided according to the invention, which is arranged below the inlet connection 4 A , 5 A in a horizontal plane over the full length of the flow space 2 . The width b of the depicted in FIG. 10, baffle plate 10 is approximately equal to the inner diameter r 2 of the filler neck 4 A, 5 A. However, b may be slightly larger or smaller than 2 r (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 4 A , 5 A fluid in the central part of the flow space 2 and thus a better distribution through the intermediate spaces 14 (see Fig. 2) in the direction of the edge volume between Antidröhnblechen 11 and sheath 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 ' ₁ to P' ₆ , as shown in Fig. 3. The number n of sections per section in the exemplary embodiment 6. The baffle plate 10 has in a special version on three different types of perforations, which are characterized by different relative hole cross-sectional area. By relative hole cross-sectional areas 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 L ₁ , L ₂ , L ₃ of relative hole cross-sectional areas are used, namely

L ₁ for P ₁, P ₆, P ' ₁, P' ₆,
L ₂ for P ₂, P ₅, P ' ₂, P' ₅ and
L ₃ for P ₃, P ₄, P ' ₃, P' ₄.

The perforations are chosen such that directly below the inlet nozzle 4 A, 5 A, the relative hole cross-sectional area (L ₃₎ is the smallest and the most distant from the inlet connection 4 A, 5 A portions of the relative hole cross-sectional area (L ₁₎ is largest in order to achieve the most uniform possible fluid distribution in the flow space along the cylinder axis.

In a test-built heat exchanger, the following numbers are selected:

Diameter of the flow space: d _s = 1676 mm Radius of the opening of the filler neck: r = 348 mm Distribution length: l _v = 999 mm Length of each section: a = 333 mm Width of the sections: b = 666 mm rel. Hole cross-sections: L ₁ = 40% L ₂ = 30% L ₃ = 23% Ratio max. to min. rel. Hole cross-section: L ₁ / L ₃ = 1.74 Hole diameter: d ₁ = 8 mm d ₂ = 8 mm d ₃ = 10 mm Hole pitch: t ₁ = 12 mm t ₂ = 14 mm t ₃ = 20 mm

It is favorable in terms of production to choose the length a of the sections P ₁ to P ₆ or P ₁ 'to P ₆ ' equal to the distance between two support plates 12 . Of course, in terms of distribution, a higher number of sections with different relative hole cross-sectional areas is more favorable; In the hydrodynamic calculations, a value range for the number n of sections per section of 2 to 18, preferably 4 to 8, has proven to be a practicable compromise between distribution quality and equipment complexity.

The tubes which pass through the flow space 2 are not explicitly shown in the drawings. In the longitudinal section of Fig. 1 are their straight sections between the baffle plate 10 and the support plate 15th At the ends of the heat exchanger, the tubes are connected either to one of the sockets 6 A , 6 B or to each other, as will be explained in more detail below with reference to FIG. 2.

In the cross-sectional representation 4 bundles A _{1, 2} to A _{7, 8 are} drawn, which are divided into two subgroups A ₁ , A ₂ to A ₇ , A ₈ . The subgroups consist 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 .

The tubes are connected to each other so that a fluid which is fed via the nozzle 6 A , first flows parallel through the tubes of subgroup A ₁ and then successively through the tubes of the remaining subgroups and bundles in the order A ₂ , A ₃ , A ₄ , A ₆ , A ₇ , A ₈ and then to the outlet nozzle 6 B is passed.

In the present process the heat exchanger is operated such that a first fluid - for example, cracked gas in an ethylene plant - one in two parallel streams through the inlet nozzle 4 A and 5 A into the flow space 2 and through the outlet nozzle 4 B, 5 B is led out again as indicated by arrows in Figs. 1 and 2. In the cross flow to a second fluid - for example, cooling water is fed through the nozzle 6 A , passed through the pipes, not shown, and taken over the nozzle 6 B again (arrows 7 in Fig. 1).

Claims (17)

1. Heat exchanger with a substantially cylindrical flow chamber (2) which is delimited by a casing (1), with a number of tubes that run through the flow space (2) in substantially the cylinder axis (8) parallel direction and at least one A pair ( 4 , 5 ) of nozzles, which are arranged opposite to each other on the cylindrical surface of the jacket ( 1 ) and 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 1, 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 integrally connected to one another. 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 opposing nozzles ( 4 A , 4 B , 5 A , 5 B ) and continuously over the full length of 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 ) in sections ( P ₁ to P ₆ , P ' ₁ to P' ₆ ) is divided, the different relative Have hole cross-sectional areas ( L ₁ to L ₆ , L ' ₁ to L ' ₆ ). 7. Heat exchanger according to claim 6, characterized in that the baffle plate ( 10 ) in sections ( 20 , 20 ') is divided, each having an integer n of sections ( P ₁ to P ₆ ; P' ₁ to P ' ₆ ) and on each side either through one end ( 3 A , 3 C ) of the flow space ( 2 ) or through a precisely between two pairs ( 4 , 5 ) of nozzles ( 4 A , 4 B , 5 A , 5 B ) perpendicular to Cylinder axis ( 8 ) lying plane ( 3 B ) are limited. 8. Heat exchanger according to claim 7, characterized in that in each case a portion ( 20 , 20 ') of the baffle plate ( 12 ) an even number n of successive sections P _i i = 1 ,. , ., n , wherein in each case the sections P _i and P _{ni + 1} , i = 1 _,. , ., n / 2 with respect to their dimensions a _i , b _i and their relative hole cross-sectional area L _{i are constructed} identically. 9. Heat exchanger according to claim 8, characterized in that the number n of sections P _i ( P ₁ to P ₆ ; P ' ₁ to P' ₆ ) within a portion ( 20 , 20 ') is between 2 and 18 and that for the relative hole cross-sectional areas L _{i of} the sections P _i are: L _i < L _{i +1} , i = 1 _,. , ., n / 2-1 10. Heat exchanger according to claim 9, characterized in that for the maximum relative hole cross-sectional area L ₁ : With
f : factor, 0.8 ≦ f ≦ 1.3
l _v : Verteillänge (= distance between connecting axis of a pair ( 4, 5 ) of nozzle and limitation of the corresponding section)
r : radius of the opening of the filler neck ( 4 A , 5 A) 11. Heat exchanger according to one of claims 1 to 10, characterized in that the tubes in a plurality along the connecting axis of a pair ( 4 , 5 ) of connecting pieces ( 4 A , 4 B , 5 A , 5 B ) lined up bundles ( A _{1, 2} to A _{7, 8} ) are combined, wherein the tubes are interconnected so that the bundles ( A _{1, 2} to A _{7, 8} ) are flowed through by the fluid flowing in the tubes sequentially. 12. A method of operating a heat exchanger according to claim 11, wherein each pair ( 4 , 5 ) of nozzle consists of a filling ( 4 A , 5 A ) and a drain port ( 4 B , 5 B ), a first fluid through the / the filler neck ( 4 A , 5 A ) introduced into the flow space ( 2 ) and through the drain port ( 4 B , 5 B ) is led out again and a second fluid is passed through the interior of the tubes, characterized in that the second fluid is first introduced into the tubes of the drain port ( 4 B , 5 B ) closest to the bundle ( A _{1, 2} ) and then successively the tubes of the further in the direction of inlet port ( 4 A , 5 A ) lying bundle ( A _{third , 4} to A _{7, 8} ) 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 second fluid. 14. The method according to claim 12 or 13, characterized 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 one of claims 12 to 14 in a process for recovering ethylene for cooling of cracked gas. 17. Application according to claim 16, characterized in that the first fluid consists of fission gas.