AU2016221798B2

AU2016221798B2 - Shell and tube heat exchanger

Info

Publication number: AU2016221798B2
Application number: AU2016221798A
Authority: AU
Inventors: Sayyed Ahmad FANI YAZDI; Axel Schulze
Original assignee: Hugo Petersen GmbH
Current assignee: Hugo Petersen GmbH
Priority date: 2015-02-18
Filing date: 2016-02-15
Publication date: 2020-11-12
Anticipated expiration: 2036-02-15
Also published as: DE112016000794A5; RU2017132094A; WO2016131786A1; DE102015102311A1; RU2684690C2; DE102015102311A8; BR112017017684A2; PE20180918A1; MA40804A1; AU2016221798A1; CL2017002114A1; BR112017017684B1; RU2017132094A3; FI20175825A; MA40804B1; FI130318B; MX2017010671A

Abstract

The invention relates to a shell and tube heat exchanger wherein, in order to enable uniform gas distribution in the flow around the tube bundle, a tube bundle, consisting of a plurality of tubes having at least one tube base, which is delimited to the outside by a shell surface and has a longitudinal axis extending centrally in the shell space, is arranged in a shell space, wherein the arrangement of the tubes in the tube bundle defines a tube area, which has an inner channel around the longitudinal axis which is free of tubes and an outer channel between the outer edge of the tube bundle and the shell surface which is free of tubes, wherein, according to the invention, the tube area has at least one connection zone between the inner and outer channel through which fluid enters into and/or exits from the shell space during operation of the shell and tube heat exchanger.

Description

Translation from German

A SHELL AND TUBE HEAT EXCHANGER

The invention relates to a shell and tube heat exchanger according to claim 1.

Shell and tube heat exchangers are also referred to as heat transfer apparatus and are the

heat exchangers most frequently used in industry.

In the shell and tube heat exchangers, the heat transfer surface separates a hot fluid space

from a cold fluid space. One fluid flows through the tubes (tube-side), while the other

fluid flows around the tubes (shell-side).

Tube bundles are placed into a shell and held within a tube sheet in such a manner that this

tube sheet acts as a barrier in order to prevent the mixing of the two fluids which have

different temperatures.

In order to produce a higher velocity within the shell space or to increase the contact

frequency of the medium in the shell space with the heat transfer area, baffles, deflection

segments, are used. The fluid in the shell space is thereby forced to travel a longer distance

between the inlet and outlet nozzles.

A heat exchanger of this type according to the prior art is shown in FIG. 1.

In this figure, the top illustration is a longitudinal section through a cross-flow operated

shell and tube heat exchanger. The bottom illustration shows an open perspective

representation of the shell space with tube bundle and deflection segments, baffles.

On the shell-side, the tube pitch has a strong influence on the fluid velocity and thus on the

heat transfer and on the pressure loss. Conventional cross-flow heat exchangers have non

uniform flow lines on the shell-side and, as a result, a higher mechanical load. In addition,

the pressure losses in these heat exchangers are very high.

The next step in the development of shell and tube heat exchangers were so-called radial

flow heat exchangers. A longitudinal section of this type of heat transfer apparatus is

shown in FIG. 2. The top illustration shows a longitudinal section of a cross-flow operated

shell and tube heat exchanger. An open perspective representation of the shell space with

tube bundle and baffles is shown in the bottom illustration in the figure, wherein the

respective heads for the supply and discharge of the tube-side and shell-side fluids are not

shown.

The weaknesses encountered in conventional shell-and-tube heat exchangers can be

reduced by means of a shell and tube heat exchanger with radial through-flow. As a result

of uniform flow from the central channel outwards in the radial direction or from the space

between the shell of the heat exchanger around the tube bundles to the central channel

respectively, both, lower mechanical loads and lower pressure losses in the shell space of

the heat exchanger are achieved. This results not only in freedom in the selection of the

shell-side orientation of the supply and discharge nozzles, but also in a more compact

design of the tube bundle.

When employing the radial shell and tube heat exchanger one disadvantage has to be

tolerated, namely that either a complex head and end bonnet must be constructed by

integrating the inlet as well as the outlet nozzles for the shell-side and tube-side connecting

pieces for the fluid flow through the tube bundle. Alternatively, the connecting pieces for

the fluid inlet or outlet on the shell-side must be positioned directly onto the shell, which

would be at the expense of a uniform flow in the respective inlet or outlet chamber.

It is the object of the present invention to provide a uniform flow from the central channel

outwards towards the shell surface, or rather from the space between the shell of the heat

exchanger around the tube bundles towards the central channel, and at the same time

permit a structurally simple fluid supply into and fluid discharge from the shell space.

In particular, it is an object of the invention to provide a pressure loss on the shell-side of

the shell and tube heat exchanger which is comparable to that of a shell and tube heat

exchanger offering comparable heat transfer performance.

It is a further object of the invention to reduce the structural size of a shell and tube heat

exchanger whilst providing comparable heat transfer capacity.

These tasks are achieved in a surprisingly simple manner with a shell and tube heat

exchanger according to Claim 1.

Further advantageous developments are described in the dependent claims.

The invention relates to a shell and tube heat exchanger, wherein a tube bundle comprising a

plurality of tubes having at least one tube sheet are arranged in a shell space, which is delimited

to the outside by a shell surface and has a longitudinal axis extending centrally in the shell space,

wherein the arrangement of the tubes in the tube bundle defines a tube layout, which has an inner

channel around the longitudinal axis which is free of tubes and an outer channel between the

outer edge of the tube bundle and the shell surface which is free of tubes, wherein, according to

the invention, the tube layout has at least one connection zone between the inner and the outer

channel through which fluid enters into and/or exits from the shell space during operation of the

shell and tube heat exchanger, wherein the connection zone is formed by a segment of the

circular cross section of the tube layout where tubes are missing, and wherein the tubes of the

tube bundle are encased solely by the shell surface in a direction perpendicular to their

longitudinal axis so that, during operation of the shell and tube heat exchanger, the medium can

freely flow around the entire tube bundle between inner channel and outer channel.

In the following, a basic form of a radial shell and tube heat exchanger shall serve as an example

to explain in more detail the mode of operation of the solution according to the invention. In a

cylindrical heat exchanger, having a tube area with circular cross-section, the tubes are, in

principle, arranged radially in relation to one another. In this configuration, the tube bundle is

arranged in such a way that it does not form a complete ring bundle but, due to the connection

zone, a segment of the circular cross-section of the tube area, which can be of any configuration,

is kept open in the tube arrangement. This design combines the advantages of a conventional

shell and tube heat exchanger, in particular a so-called cross-flow heat exchanger, with a radial

4A

shell and tube heat exchanger. Thus, by virtue of the invention. a better heat transfer is made

possible by reducing, at the same time, pressure loss in the shell space. In addition, during

operation of the heat exchanger according to the invention, lower mechanical loads are realised

(text continues on page 5) compared to those of conventional shell and tube heat exchangers, without a structurally complex head and end bonnet being required. Instead, a conventional type of bonnet, following the tube sheet in the longitudinal direction of the heat exchanger, can in principle be dispensed with. In this way, the invention allows for a more compact and thus also smaller size to be achieved.

The shell and tube heat exchanger according to the invention may be summed up as

achieving a "semi-radial flow". A heat exchanger according to the invention is therefore

also referred to as a "semi-RF heat exchanger". The term "semi" should be understood to

mean that only a part - not necessarily half - of the tube field layout is equipped with

tubes.

The shell space is delimited to the outside by the shell surface substantially parallel to the

envelope around the tube bundle. Within the scope of the invention the tube bundle can, in

principle, be configured to have any external shape.

In particular, the outer boundary of the tube bundle, viewed in cross section, can be defined

by a circle, a polygon, for example a rectangle, preferably a square, or an ellipse.

The tubes of the tube bundle are in particular, already due to the presence of the shell

surface, enclosed in one direction perpendicular to their longitudinal axis and/or the

longitudinal axis of the shell and tube heat exchanger so that, during operation of the shell

and tube heat exchanger, the medium can freely flow around the entire tube bundle

between the inner channel and the outer channel. As a rule, the tube bundle is generally

connected by means of its first tube sheet to a supply chamber for the supply of a tube space medium flowing through the tubes during operation of the shell and tube heat exchanger and, with its second tube sheet, to a discharge chamber for the discharge of a tube space medium flowing through the tubes during operation of the shell and tube heat exchanger, so that the tubes open into the supply or discharge chamber respectively.

In a special embodiment, the tubes of the tube bundle can also be held by a single tube

sheet only and, in the process, can be guided between their two passages through the tube

sheet by having deflections, for example, they may be bent in a U shape. The supply and

discharge chambers can then be accommodated adjacent to one another in a single end

bonnet.

The "connection zone" of the shell and tube heat exchanger according to the invention is

the region, in which the flow resistance for the shell-space fluid relative to the flow

resistance for the radial flow around the tube bundle is reduced. In this region, the packing

density of the tubes in the tube bundle is reduced.

In particular, the connection region within the tube field layout can be free of tubes.

The number of tube passages through a surface perpendicular to the longitudinal axis is

smaller in the connection zone than in the region of the tube field layout being located

outside of the connection zone.

The wording that, during operation, fluid enters into the lateral space through the

connection zone "and/or" exits out of the shell space, addresses a construction form within

the scope of the invention, according to which the heat exchanger can have a plurality of

chambers, so that in a first chamber the supply of shell space fluid can take place via the

connection zone and the discharge of shell space fluid from the heat exchanger can take place in a last chamber via the connection zone. If the heat exchanger has a single chamber, the first and last chamber are one and the same and the shell-space fluid flows solely through this chamber.

In a structurally simple embodiment, the tubes of the tube bundle are arranged with their

longitudinal extension parallel to the longitudinal axis. The parallel alignment of the tubes

is not essential, for example, the tubes can each also run on a spiral path around the

longitudinal axis in the shell space.

According to an advantageous development of the invention, the shell and tube heat

exchanger has a single chamber.

In particular, the shell and tube heat exchanger having one chamber is designed as a

module for a multi-part shell and tube heat exchanger in that the outlet from the discharge

chamber is designed to connect to the inlet into the entry chamber. This allows a plurality

of shell and tube heat exchangers to be connected to form a type of tower or stack inside

which, during operation, the shell-space fluid after leaving one heat exchanger module

enters the next module.

In order to be able to realise longer flow paths with the highest possible driving gradient

for the heat transfer, in one development of the invention the shell and tube heat exchanger

has two or more, preferably up to twenty, chambers around a single tube bundle, wherein

at least one deflection segment for the shell space fluid is arranged between adjacent

chambers.

During operation of the shell and tube heat exchanger, the shell-space fluid enters into the

first chamber which, apart from the shell surface and the edge of the connection zone

between the inner and outer channel of the tube field layout, is delimited by a tube sheet

and a deflection segment, baffle.

The baffle consists of a plate with a surface perpendicular to the longitudinal axis, which

corresponds inversely to the tube field layout, wherein an inner region is cut out of this

surface or an outer region is cut off.

In particular, the cross section of the inner region practically corresponds to that of the

inner channel, and the cross section of the outer region is practically identical to that of the

outer channel.

According to the invention, a structurally simple connection to apparatus arranged

upstream or downstream is made possible in that the shell and tube heat exchanger has a

supply device for shell space fluid into the inner or into the outer channel and a discharge

device for shell space fluid from the outer or from the inner channel, wherein the

connection zone between inner and outer channel is an integral component of the supply

device or the discharge device.

In the event of an odd number of chambers, the direction of flow of the shell space fluid

through the supply device and the discharge device in relation to the longitudinal axis is

the same. This means that, through the supply device and through the discharge device, the

shell-space fluid flows onto or away from the longitudinal axis.

In the event of an even number of chambers, the flow direction of the shell-space fluid

through the supply device is opposite to the flow direction through the discharge device in

relation to the longitudinal axis. That is to say, that the shell space fluid flows through the

supply line onto the longitudinal axis (away from the longitudinal axis) and through the

discharge line, the shell-space fluid flows away from the longitudinal axis (onto the

longitudinal axis).

Within the scope of the invention, the tube bundle can in particular have a circular cross

section, so that an inner structure of the shell and tube heat exchanger can be produced in a

structurally simple manner which, during operation, ensures a particularly uniform flow of

the shell-space fluid around the tubes.

The tube bundle can be arranged concentrically to the longitudinal axis. In a further

development of the invention, the tube bundle is arranged eccentrically to the longitudinal

axis, as a result of which, by means of the positioning of the tube bundle, an additional

option is created to influence the flow within in the shell space.

In an advantageously simple embodiment, the connection zone has a first and a second

passage surface as well as two lateral boundaries,

wherein the first passage surface is the transition area between the outer channel and the

connection zone,

the second passage surface is the transition between the connection zone and the inner

channel, the first lateral boundary extends from one edge of the first passage surface running in the longitudinal direction of the shell space to the corresponding edge of the second passage surface running in the longitudinal direction of the shell space, and the second lateral boundary extends from the other edge of thefirst passage surface running in the longitudinal direction of the shell space to the corresponding edge of the second passage surface running in the longitudinal direction of the shell space.

The two lateral boundaries of the connection zone run essentially parallel to each other,

when the connection zone is intended to realise the shortest path between the inner and the

outer channel.

Within the scope of the invention, in a direction perpendicular to the longitudinal axis or to

a parallel of the longitudinal axis, the lateral boundaries of the connection zone can, in

sections, create different cross-sectional shapes of the connection zone. The cross section

of the connection zone is the surface through which the shell space fluid passes when it

flows between the inner and the outer channel.

The invention offers a multitude of options for designing the geometry of the connection

zone in such a manner that it is adjusted to achieve the desired flow profile of the shell

space fluid and thus also the kinetics of the heat transfer during operation. Examples for

the design of the geometry of the connection zone are described in more detail below with

reference to the attached figures.

A further advantageous embodiment of the invention relates to the tube bundle consisting

of at least two, preferably three or four or five tube bundle modules. Thus, a construction of a desired tube bundle with a connection zone according to the invention is realised with pre-fabricated modules following the modular principle.

The tube bundle modules can be identical in this case.

In particular, n -1 (for example three) tube bundle modules having a cross-section - seen

perpendicular to the longitudinal axis - which is a substantially 1/n-circle (for example

quarter-circle) tube field layout, are connected to one another, wherein the connection

zone is produced by the nth (for example fourth) module which is absent in relation to the

full circle. The tube bundle modules are preferably connected in a simple manner by

insertion into the at least one tube sheet.

In a further embodiment of the invention, at least one tube bundle module is designed to be

non-identical to the at least one other tube bundle module. In particular, according to this

embodiment, one tube bundle module comprises a section of the tube layout having the

connection zone and adjacent tubes, while the one further tube bundle module or the

further tube bundle modules contribute the remaining tubes to the overall tube layout.

The invention also provides a tube bundle for a shell and tube heat exchanger described

above. Such a tube bundle can be manufactured and marketed separately. The final

assembly of the entire heat exchanger can then be carried out, for example, at the site of

use by installation in the shell and attaching the inlets and outlets to the connections for the

connection zone.

The shell and tube heat exchanger according to the invention can, in principle, be used for

liquid and gaseous media as well as for fluids containing liquid and gaseous media

components such as aerosols or wet steam. By virtue of its relatively high heat exchange

surface the shell and heat exchanger is particularly advantageous for use as a gas to gas

heat exchanger, that is to say, for heat exchange between two substantially gaseous media.

For example, the shell and tube heat exchanger according to the invention can be used for

heat recovery from hot exhaust gas streams. A particular area of application is their use in

the context of methods for synthesizing sulphuric acid (H2SO4).

The invention is explained in more detail below, with reference to the attached drawings,

on the basis of exemplary embodiments. Identical and similar components are provided

with the same reference symbols, wherein the features of the different exemplary

embodiments can be combined with one another

FIG. 1 shows a schematic representation of a longitudinal section of a shell and tube heat

exchanger operated in cross flow mode according to the prior art technology (top) and a

schematic open perspective representation of the corresponding shell space with tube

bundle and deflection segments (bottom);

FIG. 2 shows a schematic representation of a longitudinal section

of a radial shell and tube heat exchanger operated in cross-flow mode according to the

prior art technology (top) and a schematic open perspective representation of the

corresponding shell space with tube bundle and deflection segments (bottom), wherein the respective heads for the supply and discharge of the tube-side and shell-side fluids are not shown;

FIG. 3 shows a schematic open perspective of a shell and tube heat exchanger according to

the invention with one chamber;

FIG. 4 shows a schematic open perspective of a shell and tube heat exchanger according to

the invention with two chambers;

FIG. 5 shows a schematic open perspective of a shell and tube heat exchanger according to

the invention with three chambers;

FIG. 6 shows a schematic open perspective of a shell and tube heat exchanger according to

the invention with four chambers;

FIG. 7 shows a schematic perspective outer view of the shell space with supply and

discharge devices of the shell and tube heat exchanger shown in FIG. 6;

FIG. 8 shows a schematic representation of a longitudinal section of a further embodiment

of the shell and tube heat exchanger according to the invention;

FIG. 9 shows a schematic representation of a longitudinal section of a further embodiment

of the shell and tube heat exchanger according to the invention;

FIG. 10 shows a schematic representation of a longitudinal section of a further

embodiment of the shell and tube heat exchanger according to the invention;

FIG. 11 shows a schematic representation of a cross section through a tube bundle of a

further embodiment of the shell and tube heat exchanger according to the invention;

FIGS. 12 to 30

show schematic representations of, in each case, a cross section through a tube bundle

according to a further embodiment of the invention;

FIG. 31 shows a schematic open perspective representation of a shell and tube heat

exchanger with one chamber (top), in which the shell is arranged eccentrically with respect

to the tube bundle, and the corresponding view in cross-section (bottom).

In the figures, for the sake of clarity, the direction of flow of the shell-space fluid and of

the tube-space fluid is indicated by arrows, showing the operation of the shell and tube heat

exchanger according to the invention in principle.

According to the invention, in the simplest case, the tube field layout can have a radial

shape, that is to say it can be circular, but tubes are not arranged over the entire

circumference of the circle. Via an unoccupied gap within the connection zone the shell

space fluid can flow into the central channel of the heat exchanger. From there, the fluid

flows radially around the tubes in the direction of the shell of the heat exchanger. In a shell

and tube heat exchanger having a plurality of chambers, the fluid flows from there parallel

to the shell wall into the next chamber, where it can again flow radially through the tube

bundle to the central channel of the heat exchanger. The fluid is thus supplied to the central

channel of the next chamber. The positioning of the connecting pieces as supply and

discharge devices for the shell chamber fluid, as well as the positioning of the bonnet,

follow the same principle as that of a classical shell and tube heat exchanger, with the

difference that the tube field layout is configured according to the principle of a radial shell

and tube heat exchanger.

FIGS. 3 to 10 illustrate by way of different embodiment examples the above described

in-principle functions of the shell and tube heat exchanger according to the invention.

FIG. 3 shows a heat exchanger having one chamber.

The tube-side fluid enters via the bonnet, shown in the planar view indicated on the

perspective representation on the left, which opens towards the rear, is distributed to the tubes and exits again through the bonnet shown on the right, which opens towards the front.

The shell space fluid is fed into the connection zone through an opening located at the

bottom in the planar view of the perspective representation and exits the heat exchanger

through an opening located at the top after passing through the shell chamber The

geometry of the connection zone as well as the length of the shell space of the chamber,

which is connected to the supply or discharge device for the shell-space fluid, are

determined by the width of this chamber and the dimensions and positioning of the two

lateral boundaries of the connection zone, which lateral boundaries are represented by

blackened areas.

FIG. 4 shows a further embodiment of the shell and tube heat exchanger according to the

invention, comprising two chambers that are separated by a metal baffle in the tube field

layout. The shell-space fluid is supplied via an opening shown in the planar view of the

perspective representation at the bottom right in the connection zone and from there into

the inner channel. After passing through the first chamber of the shell space, it passes

through the outer channel, which is unimpeded by the baffle, into the second chamber and

flows through the tube area from the outside to the inside into the inner channel. From

there, the shell-space fluid leaves the inner channel through the connection zone and exits

the heat exchanger through the opening shown at the bottom left in the perspective

representation.

Further chambers can be arranged between the two chambers of the embodiment shown in

FIG. 4 in order to increase the heat exchange surface. FIG. 5 shows a corresponding heat exchanger with such an additional chamber. In FIG. 6, a corresponding heat exchanger having two such additional chambers is shown.

FIG. 7 shows an external view of the shell space of the embodiment shown in FIG. 6. A

supply and a discharge device for the shell space fluid are each placed in the form of a

bonnet on the shell space, the shell surface of which has corresponding recesses, in order to

allow the passage of the shell-space fluid from the supply device into the connection zone

of the first chamber and from the connection zone of the last chamber into the discharge

device.

FIG. 8 shows a longitudinal section through a shell and tube heat exchanger having two

chambers. In this embodiment, the supply of the shell-space fluid occurs, in the direction

into the plane of the paper, into the inner channel of the first chamber, which lies at the

bottom in the representation in FIG. 8. After passage of the tube bundle through the first

chamber, the shell space fluid flows around the deflection plate in the outer channel and

passes from the outside to the inside of the tube bundle of the second chamber, which is

shown at the top in the representation in FIG. 8. The discharge of the shell space fluid

occurs through the connection zone towards the discharge device, in the direction out of

the plane of the paper, out of the inner channel of the second chamber. The tube-side fluid

is introduced into the heat exchanger and removed from the latter via end bonnets which

are schematically represented in FIG. 8 top and bottom.

In the variant of a heat exchanger according to the invention shown in FIG. 9, the shell

space fluid is discharged directly from of the inner channel of the second chamber through

a centrally arranged discharge device.

In the embodiment of the heat exchanger according to the invention shown in FIG. 10, the

flow direction of the shell space fluid is reversed relative to the representation shown in

FIG. 9; the shell space fluid is supplied via a centrally arranged supply device directly into

the inner channel of the chamber which is then flowed through first.

The discharge of the shell-space fluid occurs, in the direction out of the plane of the paper,

from the inner channel of the chamber which then is the second chamber flowed through

via the connection zone into the discharge device.

The tube field layout can in principle have a radially arranged shape or simulate a radial

shape with the aid of a plurality of segments. The number of segments can be optional.

Within the tube field layout, the tubes can be arranged in alignment or offset relative to one

another. A further option for arranging the tubes relative to one another within the scope of

the invention is a special variant of an offset arrangement, namely the arrangement of tube

rows positioned one behind the other - when viewed from the longitudinal axis - in such a

manner that the tubes are arranged on a curved path. This arrangement is achieved when a

wall structure is made of tubes, the centre points of which are positioned on concentric

circles around the longitudinal axis. In the figures, such curved paths 28 are marked as

dotted lines.

In a preferred corresponding embodiment, the tube bundle according to the invention has at

least one segment in which tubes are arranged with their centre points on at least three

circles concentric to the longitudinal axis, in such a way that the line connecting the centre

points of a tube of one circle to a tube of the circle having the next larger diameter when

being continued on to an adjacent tube of a next circle having a larger diameter, a curved

path 28 is obtained.

The invention thus provides the possibility, for tubes on mutually adjacent circles to be

packed particularly tightly, because the distance between the circles on which the centre

points of the tubes are arranged can, given suitably dimensioned tube spacing, be selected

to be smaller than the tube radius. Such tube arrangements are realised in the tube bundles

shown in the figures.

The fluid inlet and fluid outlet gaps of the connection zone, which are formed due to tubes

missing on the tube field layout, can assume any geometry, such as for example, radial,

axial, spiral, rectangular, triangular with the apex towards the centre or outwards.

Such geometries are explained in more detail below based on the description relating to

FIGS. 11 to 31. In FIGS. 11 to 16; flow arrows are additionally drawn, showing the flow of

the shell space fluid during operation.

FIGS. 11 and 12 show a tube field layout according to an embodiment of the invention, in

which the connection zone has a constant cross-sectional area in the direction of the

longitudinal axis; the lateral boundary surfaces of the connection zone are parallel to each

other. FIG. 17 shows an alternative tube field layout with the same surface having a

different arrangement of tubes and likewise parallel walls of the connection zone. In FIG.

27 also, the lateral boundaries of the connection zone are arranged parallel to each other in

the tube field layout, wherein the connection zone guides the shell space fluid tangentially

to the inner channel (see below).

FIGS. 13 to 16, 18, 19, 21, 25, 26, 28, 29 and 30 show tube field layouts, wherein the

connection zone in the direction of the longitudinal axis tapers to an angle U (alpha). FIG.

20 shows a tube field layout where the connection zone in the direction of the longitudinal

axis expands to an angle a (alpha).

The first or the second lateral boundary of the connection zone extends radially, at least in

sections, as viewed from the longitudinal axis. Both lateral boundaries of the connection

zone can also extend radially, at least in sections, as viewed from the longitudinal axis.

Within the scope of the invention, the two lateral boundaries of the connection zone can

enclose an angle in the range of approximately 180 to approximately 10° with each other

when viewed from the longitudinal axis or in the direction from the outer channel to the

inner channel.

The vertex of the angle a does not necessarily have to lie on the longitudinal axis; instead,

its position can be selected with regard to the design of the flow profile of the shell space

fluid.

In particular, in the event of at least one lateral boundary of the connection zone being

guided tangentially to the edge of the inner channel, the vertex of the angle a does not lie

on the longitudinal axis, but in particular in the region of the inner channel outside the

longitudinal axis or in the region of the tube field layout provided with tubes.

According to a further embodiment of the invention, the first or the second lateral

boundary extends, or both lateral boundaries of the connection zone extend, viewed

perpendicularly to the longitudinal axis, at least in sections, substantially tangentially to the

edge of the inner channel.

FIG. 26 shows a variant of this embodiment in which both lateral boundaries run

tangentially to the edge of the inner channel. In the embodiment shown in FIG. 28, a lateral

boundary runs tangentially to the edge of the inner channel, whereas the other lateral

boundary of the connection zone runs radially to the longitudinal axis.

In the embodiment shown in FIG. 29, one lateral boundary runs tangentially to the edge of

the inner channel, the other lateral boundary of the connection zone runs on a spiral path,

which runs from the outer channel to the inner channel. The centre of the spiral lies in the

region of the tube layout provided with tubes that lies outside of the connection zone.

Within the scope of the invention, depending on how the flow of the shell space fluid is to

be guided in the connection zone, the first or the second lateral boundary or both lateral

boundaries of the connection zone viewed in cross section perpendicularly to the

longitudinal axis, runs or run at least in sections, along a curved path, wherein the first or

the second lateral boundary or both lateral boundaries, at least in sections, define in

particular a circular arc segment or a section of a spiral.

The radius of the circular arc segments of both boundaries can be the same or different.

The spiral has its centre in the space between the inner and the outer channel. FIG. 22

shows a tube field layout according to a further embodiment of the invention, in which

both lateral boundaries run along a spiral path.

FIGS. 24 and 25 show embodiments in which the lateral boundaries are spiral-shaped in a

first section adjacent to the inner channel and, in a second section adjacent to the outer

channel, the lateral boundaries run radially to the longitudinal axis.

The number of tubes per cross-sectional area perpendicular to the longitudinal axis in the

connection zone can be varied within the scope of the invention. In a further development

of the invention, the number of tubes per cross-sectional area perpendicular to the longitudinal axis in the connection zone is smaller than outside the connection zone, in particular, the connection zone can be free of tubes.

FIGS. 13,14,18, 19 and 23 to 25 show embodiments in which tubes are arranged in the

connection zone, however fewer tubes than in the remaining region of the tube field layout

outside the inner and outer channels. In this embodiment, the tube layout of which is

shown in cross section in FIG. 23, the tubes are arranged in the connection zone in such a

way that a double spiral path for the conveyance of the shell-space fluid is formed through

the connection zone. At least one tube, preferably a plurality of tubes, can be arranged in

the connection zone in such a way that a multi-path connection zone is realised.

Within the scope of the invention, the first or the second lateral boundary or both lateral

boundaries of the connection zone, can be clad, at least in sections.

FIGS. 12 to 21 and 26 to 30 show embodiments having such cladding in the lateral region

of the connection zone.

A metal sheet is preferred to be installed as cladding for separating the connection zone in

the region of the lateral boundary or boundaries in the tube field layout. The metal sheet is in particular designed according to the shape of the respective lateral boundary or boundaries, namely flat or curved.

In an advantageous further development of the invention, the shell and tube heat exchanger

has at least two, in particular three or four or five, connection zones which are preferably

evenly distributed in the tube layout. A tube area of such an embodiment is represented in

FIG. 30 having four connection zones. These are evenly arranged on the circumference of

the tube field layout.

The connection zones are separated from one another by regions occupied by tubes. A

plurality of connection zones can join in the outer shell, so that only one supply and one

discharge device respectively for the shell-space fluid must be connected on the tube

bundle heat exchanger. Within the scope of the invention, however, depending on the

particular application, even more supply and/or discharge devices may be arranged at the

shell and tube heat exchanger up to the number matching that of the connection zones.

A further embodiment of the invention is shown in FIG. 31, according to which the flow of

the shell space fluid is further improved with regard to a uniform gas distribution in the

tube bundle. As shown in the top illustration of the perspective view in FIG. 31, an inlet

opening is provided in the outer channel having an extension in the direction parallel to the

longitudinal axis which is larger than that in the direction perpendicular thereto. The outlet

opening which adjoins the connection zone has, in comparison with the inlet opening, a

shorter extension in the direction parallel to the longitudinal axis and a wider extension in

the direction perpendicular thereto, in particular, the outlet opening has a circular shape. In the embodiment shown, only the discharge of the shell-space fluid occurs through the connection zone. By comparison: in the embodiment shown in FIG. 1, only the supply of the shell-space fluid occurs through the connection zone.

Furthermore - and this relates to a structural measure independent of the selection of the

cross-sectional dimensions of the inlet and the outlet openings for the shell space fluid

the tube field layout is positioned eccentrically to the shell space (see bottom illustration of

Fig. 31). The longitudinal axis of the tube bundle is arranged offset relative to the

longitudinal axis of the shell. The direction of the offset widens the outer channel on the

opposite side; in the example shown the tube bundle is offset downwards, so that the outer

channel is widened at the top. As a result, the inflowing shell-space fluid can spread out

across a larger region before passing through the tubes. The eccentric arrangement of the

tube bundle can thus also lead to a more uniform gas distribution in the tube bundle.

The fluid inlet and outlet nozzles for the shell space fluid can in principle assume any

shape within the scope of the invention, for example have a rectangular, oval or circular

cross-section. The operating temperature range of the shell and tube heat exchanger

according to the invention can be between - 270 to 2000°C. The preferred operating range

is 0 to 700°C.

The tube bundles described here can be employed as shell and tube heat exchangers or

separately as part of another apparatus, as soon as heat transport takes place as a main or

secondary function.

In the following examples, the performance of two heat exchangers will be compared, that

of a so-called "semi-radial heat exchanger" and that of a conventional "radial heat

exchanger". In each example, both heat exchangers have the same tube length and the same

tube inner and outer diameter, as well as the same tube pitch. The heat exchangers

compared differ with regard to the number of tubes.

Embodiment example 1:

A semi-radial heat exchanger with tubes of 76.1 mm outer diameter with an overall heat

transport surface of 573.78 square meters is used for the heat transfer between gas flows in

a sulphuric acid plant with the following parameters.

Shell-side flow:

Volume flow 110,000 nm3/h-(Standard cubic

meter per hour)

Content of s02 in %by volume 0.35

Proportion of 02 in % by volume 6

Proportion of n2 in %by volume 93.65

Input temperature in °C 70

Starting temperature in °C 125 for semi radial heat exchanger

Starting temperature in °C 120 for radial heat exchanger

Tube-side flow

Volume flow 135 000 nm3/h-(Standard cubic

meter per hour)

Content of s02 in %by volume 0.3

Content of s03 in %by volume 9.5

Proportion of 02 in % by volume 5.5

Proportion of n2 in %by volume 84.7

Input temperature in °C 240

Starting temperature in °C 201 for semi radial heat exchanger

Starting temperature in °C 204 for radial heat exchanger

The amount of heat transferred is 607 kW.

In the case of a radial heat exchanger having the same tube pitch and the same tube

diameter and the same tube length with a heat transfer surface area of 577 square meters,

the power is only 560 kW.

Embodiment example 2

When using the same semi-radial and radial heat exchanger as in exemplary embodiment 1

in another process with the following gas composition, the radial heat exchanger has a

power of only 634 kW, while the semi-radial heat exchanger according to the invention has

a power of 677 kW.

Shell-side flow:

Volume flow 25, 000 nm3/h-(Standard cubic meter

per hour)

Content of s02 in %by volume 0.3

Content of s03 in %by volume 9.5

Proportion of 02 in % by volume 5.5

Proportion of n2 in %by volume 84.7

Input temperature in °C 430

Starting temperature in °C 198 for semi radial heat exchanger

Starting temperature in °C 213 for radial heat exchanger

Tube side-flow

Volume flow 135, 000 nm3/h-(Standard cubic

meter per hour)

Content of s02 in %by volume 0.35

Proportion of 02 in % by volume 6

Proportion of n2 in %by volume 93.65

Input temperature in °C 70

Starting temperature in °C 115 for semi radial heat exchanger

Starting temperature in °C 112 for radial heat exchanger

Embodiment example 3

In this example, the semi-radial heat exchanger according to the invention achieves the

same power as the radial heat exchanger from the exemplary embodiment 2 under the same

process conditions, that is to say a power of 634 kW. The tube diameters, tube length and

tube pitch remain the same for both heat exchangers, however, the number of tubes for the

semi-radial heat exchanger is reduced. In this case, for the specified power of the semi

radial heat exchanger, a heat transfer surface area of only 474 square meters is required,

while the radial heat exchanger has a transfer surface area of 577 square meters.

Shell-side flow:

Volume flow 25 000 nm3/h-(Standard cubic meter

per hour)

Content of s02 in %by volume 0.3

Content of s03 in %by volume 9.5

Proportion of 02 in % by volume 5.5

Proportion of n2 in %by volume 84.7

Input temperature in °C 430

Starting temperature in °C 213 for semi radial heat exchanger

Starting temperature in °C 213 for radial heat exchanger

Tube-side flow

Volume flow 135 000 nm3/h-(Standard cubic

meter per hour)

Content of s02 in %by volume 0.35

Proportion of 02 in %by volume 6

Proportion of n2 in %by volume 93.65

Input temperature in °C 70

Starting temperature in °C 112 for semi radial heat exchanger

Starting temperature in °C 112 for radial heat exchanger

Those skilled in the art will understand that the invention is not limited to the examples

described above, but can rather be varied in many ways. In particular, the features of the

individual illustrated examples can also be combined with one another or exchanged for

each other.

LIST OF REFERENCE NUMERALS

1 Shell and tube heat exchanger

11 Chamber, first chamber

12 Last chamber

13 Supply for shell space fluid, supply device

14 Discharge for shell space fluid, discharge device

2 Tube bundle

20 Tube

21 Inner channel

23 Outer channel

24 Outer edge of the tube bundle

28 Curved path

200 Tube bundle module

25 First tube sheet

26 Second tube sheet

250 Supply chamber

260 Discharge chamber

R Tube space medium

M Shell-space medium

3 Shell space

31 Shell surface

32 Guide plate, deflection segment, baffle for the shell space fluid

33 Longitudinal axis

4 Connection zone

41 First passage surface

45 Edge of the first passage surface

42 Second passage surface

46 Edge of the second passage surface

43, 44 Lateral boundaries

430, 440 Cladding, metal sheet of the lateral boundary angle

(a = alpha)

Claims

1. A shell and tube heat exchanger, wherein a tube bundle comprising a plurality of tubes

with at least one tube sheet is arranged in a shell space,

which is delimited to the outside by a shell surface and has a longitudinal axis

extending centrally in the shell space,

wherein the arrangement of the tubes in the tube bundle defines a tube layout,

which has an inner channel, free of tubes, around the longitudinal axis and an

outer channel, free of tubes, between the outer edge of the tube bundle and the shell

surface,

wherein the tube layout between inner channel and outer channel has at least one

connection zone through which fluid enters the shell space and/or exits from the shell

space during the operation of the shell and tube heat exchanger, and

wherein the connection zone is formed by a segment of the circular cross section

of the tube layout where tubes are missing,

and wherein

the tubes of the tube bundle are encased solely by the shell surface in a direction

perpendicular to their longitudinal axis so that, during operation of the shell and tube heat

exchanger, the medium can freely flow around the entire tube bundle between inner

channel and outer channel.

2. The shell and tube heat exchanger according to claim 1,

wherein the shell and tube heat exchanger is comprised of a single chamber.

3. The shell and tube heat exchanger according to claim 1 or 2,

wherein the shell and tube heat exchanger is comprised of two or more, preferably

of up to twenty chambers around a single tube bundle, wherein between mutually

adjacent chambers a deflection segment baffle for the shell space fluid is arranged.

4. The shell and tube heat exchanger according to any one of the preceding claims,

wherein the shell and tube heat exchanger is comprised of a supply for the shell

space fluid into the inner channel or into the outer channel and a discharge for the shell

space fluid from the outer channel or from the inner channel, wherein the connection

zone is an integral component of the supply and/or the discharge.

5. The shell and tube heat exchanger according to any one of the preceding claims,

wherein the tube bundle has a circular cross section.

6. The shell and tube heat exchanger according to any one of the preceding claims,

wherein the tube bundle is arranged concentrically or eccentrically in respect of

the longitudinal axis.

7. The shell and tube heat exchanger according to any one of the preceding claims,

wherein the connection zone has a first and a second passage surface as well as

two lateral boundaries,

wherein the first passage surface is the transition between the outer channel and

the connection zone, the second passage surface is the transition between the connection zone and the inner channel, the first lateral boundary extends from an edge of the first passage surface, which edge runs in the longitudinal direction of the shell space to a corresponding edge of the second passage surface, which corresponding edge runs in the longitudinal direction of the shell space, and the second lateral boundary extends from the other edge of the first passage surface, the edge runs in the longitudinal direction of the shell space, to the corresponding edge of the second passage surface and the edge runs in the longitudinal direction of the shell space.

8. The shell and tube heat exchanger according to Claim 7,

wherein the two lateral boundaries of the connection zone, at least in sections,

extend substantially parallel to each other.

9. The shell and tube heat exchanger according to claim 7 or claim 8,

wherein the two lateral boundaries as seen from the longitudinal axis should, at

least in sections, enclose an angle a in the range of about 180° to about 10°.

10. The shell and tube heat exchanger according to any one of claims 7, 8, or 9,

wherein the two lateral boundaries in the direction from the outer channel towards

the inner channel, at least in sections, enclose an angle a in the range of about 1800 to

about 10°.

11. The shell and tube heat exchanger according to any one of claims 7 to 10,

wherein the first or the second lateral boundary or both lateral boundaries of the

connection zone, at least in sections, extends or extend radially, as viewed from the

longitudinal axis.

12. The shell and tube heat exchanger according to any one of claims 7 to 11,

connection zone, as viewed from the longitudinal axis, extends or extend, at least in

sections, substantially tangentially to the edge of the inner channel.

13. The shell and tube heat exchanger according to any one of claims 7 to 12,

connection zone) viewed in cross section perpendicularly to the longitudinal axis, extends

or extend, at least in sections, along a curved path, wherein the first or the second lateral

boundary or both lateral boundaries, at least in sections, defines or define in particular a

circular arc segment or a section of a spiral.

14. The shell and tube heat exchanger according to any one of the preceding claims,

wherein the number of tubes per cross-sectional area perpendicular to the

longitudinal axis is smaller within the connection zone than that outside of the connection

zone or that the connection zone is free of tubes.

15. The shell and tube heat exchanger according to any one of the preceding claims,

wherein the shell and tube heat exchanger has at least two, in particular three or

four or five, connection zones, which are preferably evenly distributed in the tube layout.

16. The shell and tube heat exchanger according to any one of claims 7 to 15,

connection zone is or are clad, at least in sections.

17. The shell and tube heat exchanger according to any one of the preceding claims,

wherein within the tube layout there are, at least in sections, tubes arranged with

their centre points on at least three concentric circles to the longitudinal axis, in such a

way that the connecting line of the centre points of a tube of a circle to a tube of the circle

with the next larger diameter when being continued on to an adjacent tube of the next

circle with a larger diameter, results in a curved path.

18. The shell and tube heat exchanger according to any one of the preceding claims,

wherein the tube bundle is assembled from at least two, preferably three or four or

five tube bundle modules.

19. The shell and tube heat exchanger according to claim 18,

wherein the tube bundle modules are identical.

20. The shell and tube heat exchanger according to claim 18,

wherein at least one tube bundle module is designed to be non-identical to the at

least one other tube bundle module.

21. A tube bundle for a shell and tube heat exchanger according to any one of claims 1 to 20

which, in assembled state in a shell space of the shell and tube heat exchanger is

arranged as a tube bundle comprised of a plurality of tubes with at least one tube sheet,

extending centrally in the shell space,

wherein the arrangement of the tubes in the tube bundle defines a tube layout,

which has an inner channel free of tubes around the longitudinal axis and

an outer channel free of tubes between the outer edge of the tube bundle and the

shell surface,

so that during operation of the shell and tube heat exchanger the medium can

freely flow around the entire tube bundle between inner channel and outer channel,

wherein

the tube layout, between the inner channel and the outer channel, has at least one

space during the operation of the shell and tube heat exchanger,

of the tube area where tubes are missing.

22. Use of a shell and tube heat exchanger according to any one of claims 1 to 20 as a gas to

gas heat transfer apparatus, in particular for heat recovery.

23. Use of the shell and tube heat exchanger according to any one of claims 1 to 20, as a gas

to gas heat transfer apparatus in particular for heat recovery, wherein the gas to gas heat

transfer apparatus is employed in a process for the synthesis of sulphuric acid.

State of the art

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