Note: Descriptions are shown in the official language in which they were submitted.
s~
I'he invention relates to a heat exchanger comprising at least one
bundle of parallel tubes for a fluid medium, the tubes being connected at
one end to a distribution casing and at the other end to a collection casing.
~n envelope around the tubes guides a second fluid medium around the tubes.
A distribution stage and a collection stage each comprising a plurality of
elements is arranged between the tubes and the distribution casing and the
collection casing respectively. The first medium evenly divided into dis-
tribution streams and/or these distribution streams are evenly united to a
main stream. The elements forming a distribution stage or collection stage
are constructed in the form of thin-walled boxes.
The aim of the invention is an improved heat excha~ger having a
thin-walled, box-shaped element which forms part of a distribution stage. In
the heat exchanger referred to above the box-shaped element is included in
the first distribution stage, which directly communicates with the distri-
bution or collecting casing respectively. However, these box~shaped elements
can be mounted only with difficulty in large size heat exchangers.
The invention has for its object to improve the heat exchanger
whilst maintaining a comparatively light-weight, flexible structure which is
capable of readily accommodating the stresses produced by the high temperature
variations encountered in operation.
The invention provides a heat exchanger comprising delivery and
collection casings for a first fluid medium, means for conducting the first
medium from the delivery casing to the collection casing and comprising a dis-
tribution stage connected to the delivery casing, a plurality of tubes con-
nected to the distribution stage, and a collection stage connected between the
plurality of tubes and the collection casing, and an envelope which surrounds
the distribution stage, the plurality of tubes, and the collection stage and
through which, in use, a second fluid medium flows in indirect heat exchange
relationship with the first medium in the tubes, at least one of the distri-
bution and collection stages comprising a number of pipes which lead from the
corresponding casing, and a similar number of manifolds each of which connects
; one of the pipes to a group formed by at least two of the tubes, each of the
manifolds comprising a pair of oppositely
.
;i8
facing cup-shaped thin walled ilexible members, the edges of which are
joined in a gas-tight manner to form a manifold having spaced apart sub-
stantially parallel walls with a pipe being connected to one of said walls
and the tubes forming a group of tubes being connected to the other of said
walls.
With a view to simple assembly, the ends connected to the collec-
tion and distribution casings of at least the pipes located further outwards
with respect to the plurality of ~ubes are d~rected normally to the plane of
symmetry of the exchanger. Thus a group of tubes can first be fastened to
a pipe after which this entire unit can readily be mounted on a collection
and distribution casing respectively by inserting the ends laterally into
previously drilled holes of the casing and by welding the same.
The invention will be described more fully with reference to the
accompanying drawings, wherein:
Figure 1 is a schematic cross-sectional view of a heat-exchanger
embodying the invention;
Figure 2 shows a detail of the second distribution stage between
a pipe and the tubings;
Figure 3 is a cross-sectional view in detail of the end of a tubing
connected to the lower half of a box-shaped element of Figure 2;
Figure 4 is a cross-sectional view in detail of a completed box-
shaped element connected to a tubing and to a pipe;
Figure 5 is an elevational view taken on the line V-V in Figure 2,
and
Figure 6 is a sectional view taken on the line VI-VI in Figure 2.
In the embodiment to be described the heat exchanger comprises a
plurality of tubes 1 connected at their upper and lower ends to a distri-
bution casing 2 and a collection casing 3 respectively. The tube conduct
one medium from the distribution casing 2 towards the collection casing 3,
whereas the other medium is guided around the tubes 1 by a surrounding
envelope 6. The other medium flows, as shown in Figure 1, from bottom to
top in the direction of the arrows Pl so that heat exchange takes place
between the two media in counterflow.
The one medium from the casing 2 is divide~ into smaller distri-
bution streams before it reaches the tubes 1. These distribution streams
are collected stepwise into a main stream entering the collection casing 3.
This distribution or collection i5 done by pipes 7 connected to the casings.
To distribute the partial streams to each pipe second stage connected
elements are employed, which are connected to a number of tubings 1. In
Figure 1 the pipes 7 and the tubings 1 are indicated only by lines.
Figures 2, 3, 4 and 5 show the second stage element 8 in detail.
The element 8 consists mainly of a flat box formed by two confronting cup-
shaped portions 81 and 82 (see Figures 3 and 4), whose edges are joined at
83 in gas-tight manner. In the embodiment shown this is formed by welding.
In the top wall of the upper cup-shaped portion 81 the pipe 7 is centrally
fastened so that it opens into the hollow cavity formed by the two cup-
shaped portions 81 and 82.
If the heat exchanger employs only a single-walled pipe for the
tubes 1, this may be compared with the outermost pipe 11 in Figures 3 and 4,
which is secured to the lower cup-shaped portion 82 of the element 8 so that
it opens into the hollow cavity of the element 8. From the drawings it will
be apparent that in each case three of the tubes 1 are fastened to each
element 8, so that the second stage divides the stream from a pipe 7 into
three partial streams in the tubes 11, or unites the partial streams from
three tubes 11 to a single main stream in the pipe 7.
In the embodiment shown a double-walled tube is used for the tubes
1 rather than a single-walled tube. Thus, within the outer tube 11 is a
coaxial ilmer tube 12, through which flows the medium in the envelope 6. For
correct guiding the inner tube 12 is extended axially beyond the ends of
outer tube 11 so that it projects beyond the wall of the element 8, that is
to say, across the cup-shaped element 81 (see Figure 4). Thus the medium
Elowing between the tubes 11 and 12 passes through the elements 8 the pipes
8~8
Figures 3 and 4 illustrate the simple mode of mounting, made
possible by the element 8. First the cup-shaped portion 82 is welded to the
outer tube ~1 of the double-walled tube as is shown in Figure 3. Sub-
sequently the upper cup-shaped portion 81 is welded to the inner tube 12,
after which the two cup-shaped portions 81 and 82 are joined to form a single
element 8 by welding the edge parts at 83. Flnally the pipe 7 can be welded
centrally of the cup-shaped portion 81.
The plan view of Figure 5 shows that the element 8 is of essential-
ly triangular shape. The sides of the triangle are concave at 84 to an
extent such as to follow as far as possible the circumference of the outer
tube 11 which has cooling vanes 13 secured thereto (see Figure 2). In this
way the medium flowing along the cooling vanes 13 is restricted as little as
possible by the element 8, as a result of which the overall resistance of
the heat exchanger is lower. Nevertheless owing to this structure the
relative flexibility of the tubes is ensured, since the element 8 is thin-
walled and the top and bottom walls of the cup-shaped portions 81 and 82 are
capable of moving relative to one another.
To facilitate assembly, the ends of the pipes 7 joining the dis-
tribution and collection casings respectively are arranged at right angles
to the plane of symmetry I-I (see Figure 1). This applies to at least the
pipes connected to the outer ones of the bundle of tubes 1. It is now
possible first to connect the casings 2 and 3 to the inner pipes 7, after
which the outermost pipes 7, which have previously been united with the
tubes 1 via the elements 8 can be readily fastened to the casings by sliding
the unit laterally at right angles to the plane of symmetry I-I inwardly
and by welding it.
Within the scope of the invention other arrangements of the various
elements are possible. Each pipe 7 may co-operate with more than three tubes
of the tube bundle 1, the shape of the distribution element 8 being adapted
accordingly. Furthermore the pipes 7 may be proportioned so that all of the
elements 8 are located at the same level, and not alternat~ with one another,
as shown in Figure 1.
--4
. ,
