Note: Descriptions are shown in the official language in which they were submitted.
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A heat exchanger for an an eating furnace
for exchanging heat between two fluids
1. Field of the invention
The invention relates to a heat exchanger for an annealing furnace for ex-
changing heat between two fluids, comprising a tubular profile which comprises
heat exchanger fins on its outside jacket and which is associated on at least
one face side with a connecting flange with at least one flow opening for one
of
the two fluids, especially a hot gas.
2. Description of the prior art
In the heat treatment of metallic goods to be annealed, the heat treatment and
the optionally necessary subsequent cooling occurs under a protective gas,
mostly nitrogen or hydrogen, or a mixture of these gases. In order to ensure a
proper protective gas atmosphere which is free from impurities and causes oxi-
dation, the supply and discharge of heat usually occurred previously through
high-temperature-resistant heat exchangers made of cast materials or ceramic.
Hot gases, especially fuel gases or the like, flow through these heat exchang-
ers or recuperators, with the hot gas passing heat to the heat exchanger and
the same passes the heat through its outer cooling fins to an annealing cham-
ber or the like. In the known heat exchangers which are made of steel tubes
this occurs in such a way that these tubes comprise cooling fins on their out-
side jacket in order to enlarge the surface area. It is disadvantageous in the
known heat exchangers however that they are made of massive heat-resistant
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material such as cast or ceramic materials, which not only increases the heat-
ing time of the heat exchanger as a result of this large thermal mass, but
also
prevents the application of especially strong dynamic temperature fluctuations
as a result of the large heat-storage capacity and reduces the effectiveness
of
the plant.
Based on the state of the art of the kind mentioned above, the invention is
based on the object of providing a heat exchanger for an annealing furnace
which is suitable for reproducing highly dynamic temperature fluctuations, as
can be required especially in the heat treatment of materials to be annealed.
SUMMARY OF THE INVENTION
This object is achieved by the invention in such a way that the profile is a
profile
tube made of a folded sheet whose heat exchanger fins aligned in the longitu-
dinal direction of the profile are formed by the corrugated profiles,
especially
the corrugated flanks, of the folded sheet.
The invention provides an especially simple and cost-effective possibility for
producing a heat exchanger which is suitable for an annealing furnace which as
a result of its low inherent heat storage capacity can realize especially
dynamic
temperature fluctuations in the annealing furnace in combination with an espe-
cially low material input and thus low weight. Since the profile is a profile
tube
made of folded sheet, not only the outside jacket surface of the heat
exchanger
increases in the heat exchanger in accordance with the invention, as is the
case in the state of the art, but also the inside jacket surface of the heat
ex-
changer, thus better utilizing the energy contained in the hot gas on the one
hand and enabling the realization of higher thermal energy flows with heat ex-
changers that are of the same size in respect of the state of the art on the
other
hand. If the same energy quantities need to be transported in relation to the
state of the art, the invention offers the advantage that smaller and lighter
heat
exchangers can now be used. As a result of the lower wall thickness of the
heat
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exchanger in accordance with the invention, the thermal conductivity of the
heat exchanger material can virtually be ignored and the efficiency of the
heat
exchanger increases by a relevant factor.
In order to enable the better utilization of the energy contained in the hot
gas
and to improve the heat transfer between the fluids and the heat exchanger,
turbulators could be associated with the heat exchanger fins on the inside
jack-
et side of the profile tube and/or on the outside jacket side of the profile
tube,
which turbulators lead to an improved heat transfer by turbulences applied to
the fluid flow.
In the simplest of cases, the profile tube can be provided on both face sides
with a connecting flange with at least one flow opening for one of the two pro-
files and a heat carrier fluid flows in the axial direction through the heat
ex-
changer during operation.
As an alternative to this, the profile tube can be provided on one of the two
face
sides with a connecting flange with at least one flow opening for one of the
two
fluids, with the other of the two faces sides being sealed. Especially advanta-
geous constructional conditions are obtained when a fluid tube is provided
which is coaxial to the profile axis and penetrates the connecting flange and
protrudes in the direction of the sealed face side. The heat carrier fluid can
be
introduced into or removed from the heat exchanger through said fluid tube,
which fluid can be removed from the heat exchanger or introduced into the
same through a coaxial opening in the connecting flange. Annealing furnaces
with heat exchangers that require little space can thus be realized.
The flow opening of a heat exchanger in accordance with the invention is pref-
erably associated with a flue of a burner which is optionally operated with a
por-
tion of the preheated heat exchanger exhaust air, which is a portion of the
hot
gases exiting from the heat exchanger, which is virtually for subsequent com-
bustion.
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BRIEF DESCRIPTION OF THE DRAWINGS
The invention is schematically shown in the drawings by reference to an em-
bodiment, wherein:
Fig. 1 shows a heat exchanger in accordance with the invention in a longitudi-
nal sectional view;
Fig. 2 shows the heat exchanger of Fig. 1 in a sectional view along line II-II
of
Fig. 1;
Fig. 3 shows a constructional variant of the heat exchanger of Fig. 1 in a
longi-
tudinal partly sectional view;
Fig. 4 shows the heat exchanger of Fig. 1 in an enlarged oblique view.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A heat exchanger 1 for an annealing furnace for the exchange of heat between
two fluids, a hot gas 2 flowing through the interior of the heat exchanger and
an
interior of an annealing furnace to be heated by the heat exchanger comprises
on at least one face side 3 a connecting flange 4 with at least one flow
opening
8 for one of the two fluids. A flue of a burner can optionally be inserted in
said
flow opening 8. The heat exchanger 1 is formed by a profile which in accor-
dance with the invention is a profile tube 5 made of folded sheet whose heat
exchanger fins 7, which are aligned in the longitudinal direction of the
profile
tube, parallel to the profile tube axis 6, are formed by the corrugated
profile,
especially the corrugated flanks, of the folded sheet.
In accordance with the embodiment according to Figs. 1 and 2, the profile tube
is associated on both face sides with a connecting flange 4 with at least one
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flow opening 8 each for one of the two fluids which flow through the profile
tube
in the direction of the profile tube axis 9 in operation.
According to the embodiment of Fig. 3, the profile tube 5 is associated on one
of the face sides with a connecting flange 4 with a flow opening 8 for one of
the
two fluids and the other of the two face sides is sealed with a sealing plate
10.
Moreover, a fluid tube 11 is provided which is coaxial to the profile tube
axis 9,
which penetrates the connecting flange 4 and protrudes in the direction of the
sealed face side, towards the sealing plate 10. The hot gas is introduced into
the heat exchanger 1 via the fluid tube 11 and leaves the same through a coax-
ial annular gap between the fluid tube 11 and the connecting flange 4 through
the flow opening 8.
The heat exchanger 1 is produced by folding sheets with welded end pieces,
with the folding occurring without any extension on the longitudinal sides of
the
profile surfaces.
