Note: Descriptions are shown in the official language in which they were submitted.
32~89
Cooling Chamber for the Convection Coollng of Two-
Dimensionally ~rranged Material
The invention relates to a cooling chamber for
the convection cooling of two-dimensionally arranged
material in arrangements having gaps allowing
throughflow, in particular of so-called ingot stoc~s of
light metal semi-finished products of the generic type
stated in the pre-characterizing clause of Claim l.
II1 the heat treatment of stocks of material,
e.g. light metal ingot stocks, following
homogenization, highly efficient, as uniform as
possible cooling of the material must be performed.
Depending on the metallurgical/specifications, this
cooling must be controlled or interrupted by holding
phases, in which the temperature must not change.
These two-dimensionally arranged materials may,
for example, be several layers of light metal bars laid
one on the other to form a stock, the said bars being
subjected to the cooling process at an initial material
temperature of 580C. The weight of such a stock can
amount to 25 t or more. In the first few hours of the
cooling process, 8,000,000 to lO,000,000 KJ (8 - 10 GJ)
of heat energy must be removed.
These figures illustrate the problems connected
with the cooling of such a stock, in particular in view
of the fact that the temperatures of the individual
bars of such a stock, which may contain a large number
of bars, must not differ from each other by more than a
few degrees C during the cooling process.
To solve this cooling problem, it is customary
to place the stock to be cooled in a chamber, the so-
called "cooling chamber", in which a circulation of air
is generated by the aid of fans. Such cooling chambers
are divided into two basic types, namely cooling
chambers which operate on the basis of an open circuit
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and cooling chambers which utilize the closed circuit
principle.
In open circuit cooling chambersl ambient air is
blown onto the stock and then withdrawn from the
cooling chamber, while, following its remsval from the
cooling chamber, the air conveyed by the fan in the
case of closed circuit cooling chambers flows through a
cooler which serves as a heat-exchanger and is in
general water-cooled, and then through the material to
be cooled.
In order to achieve the sufficient uniformity of
cooling and hence the homogeneous temperature
distribution in the cooling chamber during this cooling
process, so-called "reversing", i.e. a reversal of the
direction of flow of the blowing air is used. This
reversing is effected almost exclusively by reversal of
the direction of rotation of the axial fan used as the
flow drive. However, this simple solution, in terms of
expenditure, has one decisive disadvantage: a fan
suitable for ~eversing the flow must have neither a
preliminary nor a secondary guide impeller and in
addition must have blades which are set at 45 so that
the flow output in the two directions is at least
approximately equal. However, this restriction in the
design of the axial fan severely limits the possibility
of increasing the pressure of the blowing medium and
hence improving the efficiency, with the result that in
the case of stocks having high throughflow resistances,
as encountered in the case of two-dimensionally
arranged materials in arrangements having gaps
permitting throughflow, the large volume flows required
to achieve the high cooling rates are not achieved.
This is particularly the case when, in a closed
circuit, a cooling unit has to be flowed through.
Another solution, which is disclosed in DE-OS
3,049,162 comprises directing the flowing air onto the
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stock by means of a fan and altering the direction of
the air stream by means of an adjusting flap. however,
a device of this kind is only suitable for simple
dryers which are not expected to meet particularly
stringent requirements with regard to uniform cooling
of a large volume of material; given the stringent
requirement for a uniform temperature distribution,
such as that required
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~or the cooling of light metal, this apparatus does not
lead to the desired result.
Corresponding disadvantages also apply to the
circulatiny apparatus known from DE-OS 2,600,724.
Finally, a cooling chamber for the convection
cooling of two-dimensionally arranged material in
arrangements having gaps permitting throughflow, of the
generic type stated, is disclosed in DE-OS 3,215,509.
In this arrangement, a fan forces the gas stream
10 through the gaps in the two-dimensionally arranged
material; in order to obtain the desired uniform
temperature distribution over the whole volume of the
material, the direction of the gas stream can be
controlled by sliding valve plates similar to cover
15 plates. The fundamental disadvantage of this apparatus
lies in the fact that the flow through the gaps in the
material occurs only on the delivery side of the fan,
i.e. the air which brings about cooling is blown onto
the stock. This blowing on with the aid of jets which
pass through the gaps in the two-dimensionally arranged
material produces locally very different cooling rates
which are not reconcilable with the stringent
requirements on the uniform temperature distribution
during cooling of high-volume light metal stocks
2s following homogenization.
The present invention seeks to create a
cooling chamber for the convection cooling of two-
dimensionally arranged material in arrangements having
gaps allowing throughflow, in particular of so-called
ingot stocks of light metal semi-finished products, of
the generic type stated, in which the above-mentioned
disadvantages do not occur.
In particular, the invention seeks to provide
an apparatus which guarantees a highly uniform tempera-
3s ture distribution over the whole of the material to becooled even when extremely large masses of material
have to be treated.
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In accordance with the invention there is
provided a cooling chamber for the convection cooling
of two-dimensionally arranged material in arrangement~
having gaps allowing throughflow, in particular of
s ingot stocks o~ light metal semi-finished products,
having at least one fan deli~eIing into an exhaust
duct, characterized in thati.
i) a bifurcated pipe is arranged on a suction
side of the fan;
ii) a shut-off and regu:Lating flap is provided in
each branch of the bifurcated pipei
iii) feed ducts, which are associated with the
branches of the bifurcated pipe, are arranged
symmetrically to the material to be cooled;
15 iv) each of said feed ducts has a further shut-
off and regulating flap;
v) the shut-off and regulating flaps in the
bifurcated pipe and in the feed ducts are set so that,
by reason of the suction effect of the fan, the
material to be cooled is flowed through by the main or
a part-stream and so that the direction of flow is
reversed.
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Expedient embodiments are defined by the
features of the subclaims.
The advantages achieved with the invention are
based on the fact that an exactly defined part-stream
of the air stream drawn in by the fan flows through the
gaps in the two-dimensionally arranged material and the
material is thereby cooled, enabling the cooling to be
exactly defined. Despite this, the entire conveyed
stream is available at the fan, enabling the operating
temperature of the fan to be kept within limits by
mixing the blowing air with fresh air. This in turn
makes possible the use of industrial fans employing
conventional bearing and driving technology without the
need to employ special embodiments of high-temperature
fans.
By virtue of the arrangement of the material on
the suction side of the fan, a uniform flow through the
yaps in the material is achieved; the direction of flow
can be changed as desired by means of the flaps. In
comparison with devices in which the direction of
rotation of the fan has to be changed for this purpose,
this represents a major advantage since, in the case of
an alteration of the direction of rotation of the fan,
the latter must in each case be started, braked and
accelerated again and this leads to considerable
problems of design and wear in the case of continuous
operation. Finally, it is also possible with the
apparatus according to the invention for the gaps in
the material to be flowed through in a closed circuit,
this proving extremely advantageous particularly in the
case of holding phases.
For particular requirements, i.e., when, for
example, holding times at certain temperatures are to
be maintained using such a cooling chamber, additional
pivoted flaps can be installed in the side walls.
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Given appropriate temperature lnsulation of the
cooling chamber, the temperature of the material
scarcely alters in the holding phase, making the
additional installation of a heating facility
superfluous in almost all cases.
The invention is explained in greater detail
below by means of an exemplary embodiment, with
reference to the attached schematic drawings, in which:
Figure l shows a cross-section through a cooling
chamber, and
Figure 2 shows the cooling chamber according to
Figure l, partly in longitudinal section and partly in
side view.
The cooling chamber which can be seen in the
figures and is indicated in general by the reference 10
accommodates an ingot stock 12 which, according to the
representation of Fig. l, consists of a stock of
several layers of light metal bars. The ingot stock 12
rests on a conventional support 14, the height of which
can be adjusted by means of a schematically indicated
adjusting device.
Gaps through which a cooling medium, in general
air, flows in a manner which will be explained below
are necessarily formed between the individual light
metal bars of the ingot stock 12.
The ingot stock 12 is surrounded by a thermally
insulated housing 16 having side walls 16a and an
intermediate ceiling 16b, the said housing being at
such a distance from the lateral surfaces of the ingot
stock 12 that ducts 13a, 13b for the feeding and
removal of the blowing air are formed between the side
walls 16a of the housing 16 and the ingot stock 12.
A powerful axial fan 18, which has a secondary
guide impeller and delivers into an exhaust duct 20
arranged vertically above the axial fan 18l is arranged
vertically and symmetrically above the ingot stock 12,
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i.e. above the intermediate ceiling 16b. This exhaust
duct 20 can be completely or partially closed by a
shut-off and regulating flap 22 designed as a louvered
flap.
5At least one connecting duct 24a, 24b, which is
in each case provided with a louvered flap 26a, 26b
serving as a shut-off and regulating flap, branches off
on each side from the exhaust duct 20 downstream of the
axial fan 18 but upstream of the shut-off and
regulating flap 22, as seen in the direction of flow.
These connecting ducts 24a, 24b in each case open into
a feed duct 28a, 28b arranged at the side of the ingot
stock 12. Upstream of the mouths of the connecting
ducts 24a, 24b, louvered flaps 30a, 30b likewise
serving as shut-off and regulating flaps are built into
the feed ducts 28a, 28b. Through these feed ducts 2Ba,
28b, which are in alignment with ducts 13a, 13b,
ambient air can be drawn against and through the ingot
stock 12 by the axial fan 18.
20Towards the ingot stock 12, i.e. towards the
bottom, the axial fan 18 is connected to a bifurcated
pipe 32 having a left-hand branch 32a, a right-hand
branch 32b and a header 32c. In each branch 32a, 32b
there is a shut-off and regulating flap 34a, 34b. The
25branches 32a, 32b are turned towards the ducts 13a, 28a
and 13b, 28b while the header 32c is connected to the
axial fan 18.
Finally, pivoted flaps 36a, 36b are also
provided, which are located approximately at the level
of the intermediate ceiling 16b and open or close the
ducts 13a, 13b on both sides of the ingot stock 12
between their side walls and the side walls 16a of the
housing 16.
These pivoted flaps 36a, 36b are formed by parts
of the insulated side walls 16a.
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Thus, in this cooling chamber 10, the cooling
medium, air, is drawn through the gaps in the ingot
stock 12 by the axial fan 1~, the corresponding
direction of flow being determined by adjusting the
respective louvered flaps. Since the shape of the flow
cross-sections narrows constantly towards the ingot
stock 12, jet-like applications and hence nonuniform
cooling is avoided.
If, for example, as illustrated in Fig. l, the
flow is to pass through the ingot stock 12 from right
to left, the louvered flap 34a located in the right-
hand branch 32a of the bifurcated pipe 32 is closed and
the louvered flap 34b located in the left-hand branch
32a is opened. The louvered flap 30a in the feed duct
28a must simultaneously be opened and the louvered flap
30 in the feed duct 28b simultaneously closed.
The two flaps 36a, 36b are of course open.
The air drawn in by the axial fan 18 now flows
through the feed duct 28a in the direction of the
arrows, downwards, on the right-hand side of the ingot
stock 12, through the duct 13a, through the gaps in the
ingot stock 12, upwards, on the left-hand side of the
ingot stock 12, through the duct 13b, and then through
the left-hand branch 32b of the bifurcated pipe 32 and
the header 32c to the axial fan 18, which conveys the
air into the exhaust duct 20.
A nonuni-Eorm temperature distribution in the
horizontal direction of the two-dimensionally arranged
material is produced by reason of the heating of the
air during its passage through the two-dimensionally
arranged material, making it necessary to reverse the
direction of flow at regular intervals.
With the exception of flaps 36a and 36b, the
hitherto opened flaps are for this purpose closed and
the hitherto closed flaps are opened, so that the air
is now drawn in via the feed channel 28b and flows from
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the left--hand side through duct 13b into the gaps in
the two-dimensionally arranged material 12, emerges on
the right-hand side from the two-dimensionally arranged
material 12 and then, via ducts 13a and the right-hand
branch 32a, reaches the axial fan, which conveys the
heated air into the exhaust duct 20.
By partial opening or closure of the flaps 34a,
34b in the two branches 32a, 32b of the bifurcated
pipe, it is possible to ensure that an exactly defined
part-stream of the air stream drawn in by the axial fan
18 flows through the ingot stock 12. The cooling
effect can thus be exactly proportioned.
In addition, by partial opening of the flaps 26a
and 26b in the connecting ducts 24a, 24b, the air
stream drawn off can be mixed in a controlled manner
with fresh air in order to achieve particular
temperature effects.
In addition, the operating temperature of the
fan 18 can thereby be held within limits.
For particular requirements, when, for example,,
holding times at a particular temperature are to be
achieved with the cooling chamber 10, the flaps 36a,
36b are pivoted into the ducts 13a, 13b and hence the
housing 16 is sealed. Given appropriate insulation,
the temperature of the ingot stock 12 then scarcely
alters during such a holding phase, making the
additional installation of a heating facility
superfluous in almost all cases.
Finally, by closing the flaps 30a, 30b in the
feed ducts 28a, 28b and opening the flaps 26a, 26b in
the connecting ducts 24a, 24b, the cooling chamber 10
can also be operated as a closed circuit. This is
expedient in particular when the ingot stock 12 must be
kept at a particular temperature in the holding phases.
The inlet cross-sections of the two branches
32a, 32b of the bifurcated pipe 32 and the cross-
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sections of the feed ducts 28a, 28b and of the ducts
13a, 13b are rectangular in shape; the major axls of
the rectangles corresponds to the zone length for which
a fan is provided; the transformation from the
rectangular cross-section to be circular section cross-
section of the axial fan 18 takes place in the header
32c of the bifurcated pipe 32.
The ducts 13a, 13b on the two sides of the ingot
stock 12 are provided with flow-guiding devices.
Noise control devices can furthermore be
provided in the exhaust duct 20.
In the embodiment illustrated and described, the
fan 18 is designed as an axial fan; in the same way, it
is however also possible to use a radial fan.
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