Note: Descriptions are shown in the official language in which they were submitted.
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1~th May,1982
D/Wi.
Kunststofftechnik KG
5210 Troisdorf
,
"Heat exchanger and process for its manufacture"
_____________
The invention relates to a heat exchanger be-
tween a first liquid, on the one side, and a second
liquid, or a gas or gas-mixture, on the other side, and
to a process for its manufacture.
Heat exchangers are known, which comprise a
plurality of straight tubes, arranged parallel to each
other and at a distance one from another, through which
the first liquid flows, and which are externally flooded
by the second liquid, or by the gas or gas-mixture.
Depending on the application, all the tubes of
a heat exchanger o~ this ~ype are connected in series,
or else two or more tubes are, in each case, connected
in paraIlel, and these groups are then connected in
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series. If, in order to produce an effective heat
exchanger, it~is desired to locate as many tube-pieces
as possible in a confined space, the connection of the
ends of the tube-pieces, by means of appropriate tubular
end-pieces, creates considerable difficulties, because
a connection which is proof against leakage of liquid
car. be produced only when, in producing the connection,
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free access is available to the joint, around the entire
periphery of the tube-esld. This becomes particularl~
difficult when it is desired to manu~acture a heat
exchanger of this type from plastic tubes, because the
tube-p1eces are flooded, internally and/or externally,
by aggressi~e media, which prohibit the use of metal
tubes. Depending on the plastic used, a welded
connection or a glued connection then comes into con-
sideration~ the production of which poses problems, due
to the small clearances between the ~ubes, which are
even greater than in the case of metal tubes.
In heat exchangers of this type, particular
difficulties can result if a joint proves to be leaky
only after completion of the manufacture of the entire
heat exchanger, or if a joint develops a leak at a
later time. In general~ a subsequent leak-sealing
operation inside the confined tube-bundle is no longer
possible. In such an event, the entire heat exchanger
must frequently be rejected, because a repair gives rise
to higher costs than building-a completely new unit~
The object underlying the invention is to
develop the design of a heat exchanger of the above-
mentioned type, in which the tube-pieces and connections
are made from a thermoplastic material, in such a
manner that the manufacture of the heat exchanger is
considerably simplified, and is thereby rendered less
expensive, while, at the same time, the occurrence of
leaky connections is virtually prevented, or is at
least discovered immediately.
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The object is achieved, according to the in~en-
tion, when the straight tube~pieces, which are made of
a thermoplastic material, are arranged in groups, each
comprising four tubes, their ends being connected, one
- to another, in a manner proof against leakage of liquid,
by tubular end-pieces ~hich are approximately U-shaped
and are made of the same plastic, and when several tube-
groups of this type are combined to form a tube-bundle,
which is f.itted with connecting tube-sections ~or supply-
ing and discharging the first liquid, the cohesion between
the tube-pieces and the tube-groups being ensured by
retaining plates, which are distributed over the length
of the tube-pieces, are provided with holes, and are
loosely pushed on to the tube-pieces in a manner per-
mitting shifting.
`: While the manufacturing process will be dis-
j ~ cussed again in more detail in the text which follows,
it should already be pointed out, at this point, that
the groups, which each possess four straight tube-pieces
~:~ and are combined by means of the tubular end-pieces,
: : can be manufactured and stored, prior to.final assembly,
.
as pre-manufactured assemblies, it also being possible,
if desired, to carry out a leak-test on the joints.
In any case, the construction of a tube-bundle
from tube-groups of this type, and the production of
the joints at the tubular end-pieces, are greatly
simplified by the fact that the resiliently flexible
tubes can, after pushing the retaining plates together,
be bent far apart from each other, thereby enabling
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the connections to be produced in a convenient manner.
The connections are preferably effected by
welding, provided that the plastic is suitable for this
technique, or by glueing. In order to be able to
hold the four tube-pieces of a group at small distances
one from another, and thereby to be able to accommodate
a large number of tubes in a given space, the tubular
end-pieces are nested into each other, in each case in
pairs, the one tubular end-piece engaging around the
bend of the other.
A tube-bundle of this type, assembled from
several tube-groups, is already suitable for use as a
heat exchanger, for example by placing it, or suspending
it, in baths which must be held at a specified temperature.
On the other hand, a tube-bundle of this type
can be installed in a duct, and can be flooded, at
right angles to the tube axis, by a stream of air or
gas. If, in the case of an application of this type,
it is desired to increase the number of the tube-pieces,
and thereby to increase the total heat-exchange area,
it is proposed that a heat exchanger be assembled from
several superimposed tube-bundles 9 the retaining plates
then additionally bringing about the cohesion of the
superimposed tube bundles, over and above their func-tion
as spreaders. For this purpose, the retaining plates
are provided with grooves at their ends, and are pushed
into corresponding rebated ledges on the longitudinal
edges of supports, whi~h are securely located, at in-
tervals, on a base plate. A heat exchanger of this
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type, comprising several tube-bundles, then possesses,
in addition, a casing, which is provided with flange~
at both its ends, and which can be inserted into an
appropriate duct for carrying air or gas.
The invention further relates to a process for
manufacturing a heat exchanger of the abovementioned
type. This process pushing two tubular end-pieces,
engaging one around the other, on to the four tube-
pieces of each tube-group, at one end thereof, and
connecting these tubular end pieces to the tube-pieces,
the retaining plates then being pushed on to the other,
free,ends ofthb tube-pieces of allthe tube-groups of a tube-
bundle,the tubularend~pieces t~enbeing slippedon tothe
free ends of the tube-pieces and being connected thereto,
and, finally, the connecting--tube-sections being slipped
on to the two tube-ends which rem~in open, and being
connected thereto, the connections being produced by
welding or glueing, depending on the plastic used.
If the process is initially carried out only as
far as the manufacture of tube-groups, as an intermediate
product,a comparativelylarge number of thesetube-grou~s
can be stored, if appropriate in several commonly used
lengths, and called up as needed. The second part
of the process then comprises the assembly of tube-
bundles from tube-groups of this type. The tube-
bundles, manufactured in this way, can also be put
into intermediate storage, and can either be installed
singly, for example for ~arming or cooling baths~ or
can be installe~ as multiple assemblies, depending on
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the requirement. On installation, the tube~bundles
are already checked for leak-tightness, for example by
pressurising them under water.
The process for manufacturing a heat exchanger
from a plurality cf tube-bundles of this type then takes
a very simp~le form, according to the invention, in that
the tube-bundle retaining plates, which are provided,
according to the invention,with grooves at -their ends,
are pushed into -the rebated ledges of supports, which
are attached, in an appropriate arrangement, to the
baseplate ofa duct-section which is still open.
Finally, the side wall is fitted, the connecting tube-
sections projecting through openings in the side wall,
and these through-passages are rendered leak-proof.
The connecting tube-sections of the tube-bundles are
then connected to each other by means of manifold lines.
In the text below, the invention, in illustrative
embodiments, is explained in more detail, by reference
to the drawing, in which:
Fig.l shows a partially broken-open plan view of a
; heat exchanger, according to the invention,
inserted into an air duct;
Fig.2 shows a view of the heat exchanger in Fig.l,
seen in the direction of the arrow 4, but with
the connecting duct removed;
Fig.3 shows a partial representation of the base plate
of the heat exchanger in Figs.l and 2, in
perspective, prior to assembly;
Fig~ 4 shows an enlarged representation of the portion
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of Fig.3, marked with the arrow IV;
Fig.5 shows a further enlarged partial representation,
approximately actual-size, o~ the tubular end-
pieces at the end of a tube-group;
Fig.6 shows a diagrammatically simplified sectional
representation through a bath, into which a tube-
bundlè has been inser-ted, as a heat exchanger, and
Fig.7 shows a ba-th, with a tube-bundle suspended therein,
at one side, as a heat exchanger.
- The heat exchanger, assembled, according to
Figs 1 to 5, from a plurali-ty of superimposed tube-bundles,
is located, according to Fig.l in the draught through a
duct 2,3, to which a stream of air containing acid vapours
is fed, at L~, and led away at 5. In the illustrative
embodîment described, it is intended that the acid-laden
stream of air should be cooled, from a comparatively
high temperature, to room temperature. This cooling
is carried out by heat-exchange with the cold water, which
is supplied by the manifold line 14, at 15, flows through
the tubes 11, and is drawn off, at 18, by the manifold
line 17. From the manifold line 14, a plurality of
lines lead, via connecting tube-sections 13, to the tubes
11 of the hea-t exchanger, as can be recognised from Fig.l,
in conjunction with Fig.2. These tubes are contained
within tube-bundles 12, which are assembled, in each case,
from several groups 19~ each comprising four individual
tubes (see also Fig.5).
In Fig~l, the tubes of the uppermost tube-bundle
can be recognised in -the broken-open portion of the cover
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plate, while the side view, in Fig.2, shows the position
o~ the tube-bundles, one above another. In this
Figure, however, only the two uppermost tube-bundles
12 are represented in their entirety, in order to
simplify the drawing t while the tube-bundles located
underneath are indicatedS in each case, only by in-
dividual tubes 11.
` In Figs. 4 and 5 the four tubes of a tube-
group are nlarked with the reference numbers 29,30,31 and
32. In order to retain the spacings between these
tubes, they are led through holes 27 in retaining plates
25,26. A total of four retaining plates, of this
type, are represented in Fig.l~ where they bear the
reference numbers 7,8,9 and 13.
As can be seen from Figs. 1 to 4~ the four
retaining plates o~ the tube-bundles of the heat ex-
changer represented in Fig.l are provided, at their
ends, with grooves, into which corresponding rebated
ledges of supports 21,22,23,24 engage, these supports
being attached, perpendicularly, to the baseplate 20.
As already noted, the superimposed retaining plates are
marked, in Figs. 3 and 4, with the reference numbers
25 and 26, while the four retaining plates of the
uppermost tube-bundle according to Fig.l are marked with
the reference numbers 7,~,9 and 10.
Figure 5 shows a particularly space-saving
design of the tubular end-pieces 33 and 3L~. Thus,
the longer and wider tubular end piece 33 surrounds the
bend of the other tubular end-piece 34 and, on the other
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hand, is bent inwards, in a manner such that the four
openings of these two tubular end-pieces, which receive
the ends of the four tube-pieces 29,30,31,32 are located
close beside one another
In the illustrative embodiment, the tube-pieces
and the tubular end-pieces are manufactured from hard
PVC, as are the manifold lines. Hard polyethylene,
polypropylene and polyvinylidene flu~ride have been used
in other examples. Depending on the material, the
connectlons are produced by glueing or welding.
Two illustrative embodiments for warming chemical
baths are represented in Figs. 6 and 7. In Fig~6, the
bath 36, which is to be warmed, is located in a tank 35,
a tube-bundle 37, with connecting tubes 38 and 40, being
inserted on to the bottom of this tank. Hot water is
supplied, at 39, and, after having exchanged h~at with
the bath fluid, is led away again at 41.
A tank 43, with a bath liquid 42, is represented
in Fig.7. A tube-bundle 44, with supply lines 45 and
46 is introduced into the bath vertically, in contact
with a side wall of the tank 43.
The retaining plates, which are loosely pushed
on to the tube-pieces, allow thermal expansion of the
tubes, without any resulting lateral bending of the
tube-pieces or portions thereof.
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