Note: Descriptions are shown in the official language in which they were submitted.
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I~i~h-Performance Thermal Control Ducts
The present invention relates to high-performance thermal control ducts for
heat
exchanger tubes, in which one-phase liquid or gaseous substances can be
thermally
controlled as quickly and as uniformly as possible and with as much product
care as
possible and which also function for use in microstructured apparatuses as
independ-
ently as possible of the respective viscosity of the substances to be
thermally
controlled.
Background of the invention
Product-carrying ducts, particularly in the form of pipelines, are known in
the
chemical industry. The thermal control capacity of these product-carrying
ducts is
limited, since the heat-exchanging surface is small and, depending on the flow
viscosity and thermal conduction propeuty of the respective liquid or of the
respective
gas, a temperature gradient occurs between the duct center and the thermally
con-
trolled duct inner surface. To intensify the thermal control processes in pipe
ducts,
inserts or components are known which, designated as static mixers or as
turbulence
elements, are used in ducts. through which the product flows. When these
fittings are
used, the thermal control process is improved slightly. Consequently, fated
elements
of this type, such as static mixers and turbulence elements, are soldered into
the duct
in special versions, in order to increase the heat transfer coefficient and
the surface
area of the thermal control surface in the product space.
It is known that microstructured apparatuses make it possible to have high
heat
transmission capacities. Microstructured apparatuses have parallel-arranged
product-
carrying ducts of square or rectangular flow cross section. This technique
offers a
large heat-exchanging surface in relation to the product or apparatus volume.
The
microstructure technique has the disadvantage of small flow cross sections,
which are
susceptible to clogging in the case of unfiltered substances. In production
processes,
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substances or products are often laden with impurities, so that the small ~.m-
ducts
(q,-ranged quickly become clogged and the failure of the microstructured
apparatuses
occurs. For this reason, microstructured apparatuses are usually employed only
in
process engineering processes using high-purity starting materials.
Furthermore,
microstructured apparatuses are produced by means of special and cost-
intensive
manufacturing methods, so that material-carrying duct lengths are not
available in
large lengths or dimensions because such apparatuses cannot be manufactured
economically.
:10 To improve heat exchange processes, flat tubes which are produced by the
flat-
rolling of round tubes are known from EP-A 0 659 500. In flat tubes, the
distance
from the thermally controlled duct inner wall to the duct center is reduced.
This
version has the disadvantage of a small thermal control surface and the low
stability
under pressure of the flat tubes. When materials of relatively high viscosity
are
thermally controlled in flat ducts of this type, an uneven velocity
distribution occurs,
which, in tum, generates an uneven temperature distribution in the product
stream.
Materials of high viscosity additionally generate high differential pressures,
so that,
because of the low stability under pressure, these flat tubes tend to bulge
and are not
dimensionally stable. Moreover, high differential pressures occurnng in flat
tubes
lead to the rectangular cross section of the flat tubes reforming and assuming
a round
cross section again. To increase the stability under pressure of a flat tube,
the tube
wall thickness may be increased, the disadvantage of this being that the
thermal
conduction resistance is likewise increased.
EP-A 0 302 232 discloses a flat tube for a heat exchanger, which flat tube can
be
produced from a bent sheet-metal strip. This flat tube may also be provided
with
turbulence inserts, everything being soldered together sealingly in one
soldering
operation. Such bent sheet-metal flat tubes can be used only for low
differential
pressures. As soon as the flat tube is bent up due to a high pressure, it
loses the
improved heat transmission properties. The stability under pressure of a flat
tube
described is increased by webs being worked in by folding. The webs modify the
flat
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tube to the effect that a multiple-duct flat duct with higher stability under
pressure is
obtained. The individual duct obtained in the flat tube is virtually square.
However,
the square flow cross section leads to only two thermal control surfaces being
effective. Moreover, the distance from the duct center to the inner thermal
control
surface is such as to establish a temperature gradient which prevents a
uniformly
rapid thermal control having a degree of product care. If a material of
relatively high
viscosity is to be thermally controlled at a low laminar flow velocity, the
temperature
differences in the flow cross section are particularly pronounced.
~ 0 A flat tube for heat exchangers with an elliptic cross section, turbulence
elements
being inserted into the said flat tube, is known from EP-A 0 624 771. The
turbulence
elements consist of bent wires which are subsequently pushed into the elliptic
tube
and, by virtue of the bend contour, are jammed in the elliptic flat tube.
Turbulence
inserts can be used for the thermal control of aqueous materials at high flow
velocities. The thermal control process for liquids of high viscosity with low
flow
velocities is not decisively improved by means of these turbulence elements
bent
from wire.
EP-A 1 213 SS6 describes flat tubes with a plurality of flow regions which are
arranged next to one another and which issue in a collecting tube. The flat
tubes
consist of a plurality of parallel flow ducts, so that the walls of the
individual
chambers have a pressure-stabilizing action on the shape of the flat tube. A
plurality
of parallel-arranged flat tubes which all issue into a collecting tube form a
heat
exchanger. The shape of the flat tube described is produced by the extrusion
method,
2S for example with aluminum. The production of these flat tubes is
complicated and
special tools are required. Consequently, flat tubes of this type cannot be
produced in
highly corrosion-resistant materials.
US-A S,OS0,671 discloses a panel heat exchanger formed from two sheets of
thermo-
plastic polymer.
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Finally, US-A 5,826,646 describes a flat-tubed heat exchanger consisting of
two
plates to be used in a two-phase system wherein the heat transfer fluid
flowing in the
heat exchanger tubes includes both liquid and vapor. This heat exchanger is
not that
efficient whenever only a one-phase system has to be thermally controlled.
The object, therefore, was to considerably improve the known disadvantages of
the
plate heat exchanger technology and the tubular heat exchanger technology and
to
provide high-performance thermal control ducts for use in heat exchangers for
the
thermal control of one-phase liquid and gaseous substances in production engi-
~ 0 neering (on a cm-scale), on the laboratory and industrial scale (on a mm-
scale) and in
microstructure technology (on a pm-scale), which have rapid and uniform
thermal
control having a high degree of product care aver a relatively large viscosity
range
(up to 100,000 mPas) with a simultaneously low hold-up and a large heat-
transfer
surface on the product side. The high-performance thermal control duct should
be
particularly robust and compact, so that high pressure stability (up to 500
bars) is
obtained without the high-performance thermal control duct requiring any
additional
supporting components. The requirements for compact design, low hold-up and
effective product mixing in the duct broaden the problem to be solved. In
addition,
the aim was to considerably reduce known operational problems such as fouling
and
the risk of blockages associated therewith.
Summary of the invention
The solution to the problem and therefore fhe subject matter of the invention
are
high-performance thermal control ducts for high differential pressures and
large
thermal control ranges, comprised of two sheets or layers which are laid, or
sandwiched together opposite, one on top of the other and which have one-sided
depressions introduced in their parting or contact plane, wherein the height
of the
individual high-performance thermal control duct is no greater than the
thickness of
the sheets used and the individual depressions are worked into the sheet in a
material-
removing and/or material-displacing manner and form sharp edges towards the
sheet-
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parting plane, and the sheet thickness in the region of the depressions is
reduced
locally by up to 90%, and depressions having an identical depression area and
an
identical depression volume lie next to one another in the sheet-parting plane
and
have no connection to one another, and a plurality of depressions lying next
to one
another form a depression row or depression chain,
the geometric area of each depression has a greater extent in relation to the
sheet
width than in relation to the sheet length,
.10 the larger longitudinal axis of each depression is at an angle a. of 5 -
85 degrees to the
mid-axis of the depression row or depression chain, one sheet being rotated by
I80°
with respect to the other sheet, with the result that at least three
depressions which
are at an identical angle partially overlap and/or intersect one another and
form a
throughflow duct, the flow cross section of which is in the region where the
two
sheets face each other,
and
at least one holed sheet as a turbulence exciter is inserted between said two
sheets
and the throughflow duct is stable under pressure.
The high-performance thermal control ducts according to the invention, which
in the
simplest instance constitute an individual flow duct with a unitary flow cross
section,
are eminently suitable for thermally controlling both monophase liquid and
gaseous
substances to the desired temperature quickly, uniformly and with a high
degree of
product care. They are particularly suitable in the embodiment of flat ducts
and are
therefore the most suitable for use in heat exchangers where liquids (or
gases) have to
be cooled down or heated up within a very short tin-le.
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Detailed Description
The high-performance thermal control ducts according to the invention, formed
from
a multiplicity of identical depressions which have sharp edges towards the
plane
parting the sheets and are positioned one behind the other, form, in the
region where
the two sheets face each other, a flow cross section which is constant over
the entire
sheet length or duct length, so that, at the same time with a complete inflow
into the
flow cross section and a complete outflow from the high-performance thermal
control duct, a uniform flow viscosity profile which is akin to a plug flow is
,1O maintained, so that even under laminar to turbulent flow conditions, a
narrow dwell-
time spectrum allows the thermal control of temperature-sensitive substances
in an
extremely short time (within the millisecond range). In addition, the high-per-
formance thermal control duct is insensitive towards pressure variations in
the
throughflow, so that an identical flow velocity profile always prevails.
It is therefore also an object of the present invention that the supplying and
dis-
charging cross sections for the fluid are equal to or greater than the flow
cross section
of the high-performance thermal control duct, the said flow cross section
being
constant over the entire length.
When a flow passes through the high-performance thermal control duct, a narrow
or
small dwell-time spectrum is formed, and the flow of the product to be
thermally
controlled is constantly redirected and mixed completely, vertically and
horizontally,
over the entire flow cross section, so that temperature differences occurring
between
the thermally controlled wall and the middle flow region when the fluid flows
through in the high-performance thermal control duct are quickly compensated,
and
there is no temperature-induced product damage. In addition, because of the
uniform
temperature spectrum in th.e product-side flow cross section, thermal control
always
takes place with a maximum possible temperature difference.
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Adjacent depressions forming a row of depressions in a high-performance
thermal
control duct have depression areas which are identical in the sheet plane,
although
the depression volume of adjacent depressions can vary in size, so that
locally higher
flow speeds and lower hold-ups are produced, while the heat-exchange surface
area is
reduced. Surprisingly it was found that, despite a smaller heat-exchange
surface
area, the thermal control capacity is not proportionately reduced.
Another preferred object of the present invention is the fact that adjacent
depressions
having an identical depression area in the sheet-parting plane have different
,10 depression volumes and form a high-performance thermal control duct which
thus
has sections having different hold-ups and different flow speeds.
A high performance thermal control duct formed from different, alternating
depres-
sion volumes, as a result of which adjacent depressions having different
depression
heights are incorporated in individual sheets of the same thickness, can also
be
obtained by using two sheets of varying thicknesses to form a duct, in which
the
depressions locally produce an identical reduction in sheet thickness, as a
result of
which different flow speeds are produced in each sheet.
Another preferred object of the present invention is the fact that a high-
performance
thermal control duct consists of two sheets of different thicknesses, in which
depressions having identical depression areas in the sheet-parting plane but
identical
or different depression volumes are incorporated and depressions having
different
volumes axe positioned alternately in the direction of flow in one sheet or
alternately
in both sheets.
Alternately varying depression volumes in the sheets produce a pulsating flow
speed
in the direction of flow, while acting against fouling.
The high-performance thermal control ducts according to the invention are
particu-
larly suitable for the thermal control of batch materials of the most diverse
viscosi-
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ties, preferably in a viscosity range of between 0.1 mPa~s to I00 000 mPa~s,
particu-
lady preferably of 0.1 mPa~s to 10 000 mPa~s.
With the respective viscosity of the batch material, the flow processes in the
high-
performance thermal control ducts according to the invention lie in the
laminar to
turbulent range, and, depending on viscosity, differential pressures of 0.1
bar to
500 bar, preferably of 0.1 bar to 100 bar, and particularly preferably of 0.1
to 50 bar,
prevail.
fi10 The high-performance thermal control ducts according to the invention are
particu-
lady suitable for thermal control in a wide temperature range of -80°C
to 500C,
particularly for a temperature range of -20°C to 325°C and,
particularly preferably,
for the range of 20°C to 200°C.
The large temperature range, particularly in combination with the various
materials
employed, allows use for almost alI set objects.
In the high-performance thermal control ducts according to the invention,
however,
two or more substances may also be thermally controlled simultaneously. In
this
case, it may happen that these react with one another and release reaction
heat which
has to be discharged directly. It was shown that, owing to the geometry of the
depressions, the high-performance thermal control ducts according to the
invention
have a large heat-transfer surface on the product side and a lower hold-up
than
comparable thermal control ducts known from the prior art. At the same time,
because of their internal geometry, the high-performance thermal control ducts
according to the invention exert a high mixing action over the entire flow
cross
section on the substances flowing through and thus avoid temperature gradients
in
the liquid or gaseous medium/mixture flowing through.
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The subject of the present invention is therefore also that the high-
performance
thermal control duct is employed as a flow reactor when two different
substances,
which together generate a new substance, are supplied.
It has been found that the low product-side volume due to the volumetric
geometry of
the depressions and the good intermixing by means of the sharp-edged
depressions
have a positive effect on the dwell-time spectrum. Particularly where
substances of
higher viscosity are concerned, the dwell-time spectrum is markedly reduced,
as
compared with the thermal control ducts from the prior art.
,l 0
The sharp-edged transitions to the depressions prevent wedge-shaped gaps in
the
region of the sheet-parting plane, so that no product deposits occur in these
regions
and fouling is avoided.
1.5 The large number of depressions in the sheets or in the sheet layers which
lie next to
one another and have a large extent in .relation to the sheet width and which
form a
depression row or depression chain have no connections to one another in the
respective sheet plane (Fig. 1). As soon as two sheets are laid together and
identical
or similar depression rows lie with their depression areas and depression
volumes
20 directly opposite one another, partially overlapping and intersecting
cavities located
opposite one another are formed (Fig.2). A liquid or gaseous material flowing
through flows back and forth between the depressions of the two sheets and the
fluid
is constantly intermixed. Consequently, no pronounced temperature gradients az-
ise,
and a rapid and uniform thermal control of the material flowing through takes
place.
25 The longitudinal axis of the depression, the said longitudinal axis being
at the angle
oc, and consequently also the delimiting walls of the depressions act as guide
surfaces
or deflecting contours (Fig. 2). Ntoreover, they assist a transverse flow in
relation to
the longitudinal axis of the depression. Temperature-sensitive substances can
be
protected, by virtue of the mixing action, against thermal damage.
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The introduced depressions have their largest area at the surfaces of the
sheets or
layers upon which they are formed, i.e., in the "parting" or °'contact
plane'° of the
layers. With increasing parallel distance from the parting or contact plane
(i.e., from
the surface into the interior of the sheet or layer), the geometric area of
the depression
decreases. Inclined surfaces at an angle to the overall flow direction through
the
thermal control duct are thus formed in the layers from the contact plane up
to the
maximum depression height. These surfaces or guide surfaces may be straight or
curved, so that they steer the material flowing through into the depressions
located
opposite one another and assist a positively guided flow.
,10
The large number of depressions in the sheets or in the sheet layers which lie
next to
one another and have a large extent in relation to t'.he sheet width and which
show a
depression row or depression chain have the same depression area but the
depression
volume might differ in a depression row. Surprisingly, higher local flow
velocities
and a smaller hold-up and a different pressure loss are formed at the same
time. It is
therefore an object of the present invention that depression rows with the
same
depression area in the same sheet Iayer are formed but with a different
depression
volume.
The lateral surfaces, inclined or curved in the flow direction, of the
depressions are at
an angle (3 from the contact plane to the highest Ievel of the depression. In
other
words, if an imaginary line is drawn from the highest point of the rib formed
by two
depressions lying next to one another and located at the level of the contact
plane to
the lowest point of the depression, this imaginary line forms an angle (3 to
the contact
~5 plane or to the overall flow direction.
These curved or inclined surfaces assist the "vertical mixing effect" and
steer the
material flowing through into the opposite depression row. The curved or
obliquely
set surfaces counteract possible material deposits, =particularly at
prevailing laminar
flow velocities so that the flow passes through all the regions of the high-
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performance thermal control duct efficiently and uniformly. If the lateral
surfaces are
straight, they are at a preferred angle (3 of 60 degrees.
In all preferred versions, the lateral surfaces of the depressions in the
layer are at an
angle (3 of 20 to 80 degrees, preferably at an angle of 40 to 60 degrees.
The opposite lateral surfaces of a depression 2 in Fig. 1 a in a layer may
differ from
one another, so that the surface 3 on the inflowing side of the depression has
an angle
of (3' and the surface 3' on the outflowing side is at an angle ~3. The two
angles (3 and
:10 (3' have an angle of 20 to 80 degrees.
The high-performance thermal control ducts may advantageously be produced, for
example, from sheets having thicknesses of 0.5 mm to 50 mm.
Since the longitudinally extended depressions are transverse or at an angle to
the
overall flow direction, the medium flowing through in the high-performance
thermal
control duct is divided once or more than once and is subsequently combined
again
and thereby constantly intermixed, so that there are no temperature peaks and
rapid
temperature equalization and therefore thermal control having a high degree of
product care take place.
The longitudinally extended depressions preferably assist the "horizontal
mixing
effect" on the material flowing through.
The length of the depression, the said length being determined at right angles
to the
main flow direction, is identical to the inner width of the flat duct and is
smaller than
the layer or sheet width. The doubled depth of the depression in the
individual sheet
is identical to the internal height of the flat duct and is always smaller
than twice the
sheet thickness. This results in the gross flow cross section of the flat
duct. The
3~0 depression row is always equivalent to the individual high-performance
thermal
control duct.
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The center-to-center distance between two depressions of a depression row is
at least
as great as the width of the depression, in order to design a low-gap thermal
control
duct. A preferred ratio may be formed in which the depression width to the
center-to-
center distance of the depressions is greater than 1. In this case, the edges
of the
depressions on the respective layer surf ace are in contact with one another
only in a
punctiform manner in the parting plane. There are no gaps which promote
product
deposits and are possibly conducive to a blockage of the thermal control duct.
~ 0 In particular versions of the high-performance thermal control ducts
according to the
invention, the ratio of depression width to center distance is greater than
0.7 to lower
than 2, preferably greater than 0.8 to lower than 1.5, and particularly
preferably the
ratio is greater than 1 to lower than 1.1.
The sheet strips or layers provided with depressions in the high-performance
thermal
control ducts according to the invention have a non-structured edge region
which is
closed sealingly during a welding or soldering operation. The welding of the
two
sheets or layers together to form a high-performance thermal control duct
leads to
pressure-tight and highly stable flow ducts.
The non-structured edge regions rnay likewise be provided, parallel to the
depression
row, with small depressions in the form of grooves, so that these depression
grooves
in the edge region function as a soldering-medium repository. For example,
pasty
solder introduced there can connect the layers to one another in a soldering
furnace.
The depression or the depression rows for forming a high-performance thermal
control duct can be introduced into the sheet or into the Layer efficiently by
means of
various manufacturing methods. Chip-removing or~ material-stripping
manufacturing
methods and also material-displacing methods may be employed. A further
manufac
turfing alternative is casting technology.
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By material-removing or material-displacing manufacturing methods are meant,
for
example, drilling, milling, planing and lathe-turning. Those material-
stripping
methods also include, for example, etching and erosion. Depending on the
depression
size and depression shape, a material-displacing forging or stamping technique
could
also be an economical manufacturing alternative. If particularly large
quantities of
identically designed layers are required, casting methods may also be
employed. The
cast layers need only be welded or soldered together to form a duct.
In the high-performance thermal control duct according to the present
invention the
heat exchange surface is increased by more than 10% in relation to the
determined
sheet surface or layer surface of the flow region of the individual layer and
in
comparison to a heat exchanger according to the prior art. In a preferred
embodiment,
the increase in the heat exchange surface is in the range of 10 to 70%,
particularly
preferably 10 to 50% in comparison to the prior art.
Casting technology also affords the possibility that a high-performance
thermal
control duct can be produced in one piece by the use of mould cores, so that a
longitudinal welding of the layers with depressions is dispensed with.
Producing a
high-performance thermal control duct by casting technology is economical
particularly when materials with high heat transfer coefficients, such as, for
example,
aluminum, chromium, nickel and copper and their alloys, can be used from the
point
of view of the relevant application.
It is therefore also inventive that a high-performance thermal control duct
can be
produced in one piece by the casting method.
In a sheet-metal plate, for example, a plurality of depression rows arranged
next to
one another in parallel can be worked in, so that, on the same principle of
two sheet-
metal plates laid one onto the other, even greater product streams can be
thermally
controlled quickly and with great care in a short time. Depression rows
arranged next
to one another in parallel in sheet-metal plates can be introduced
simultaneously in
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one operation, so that the manufacturing costs can once again be reduced
considera-
bly.
Sheet-metal plates with a plurality of depression rows form the industrial
basis for
the construction of cost-effective duct heat exchangers or plate heat
exchangers.
In a preferred embodiment, the coynponents of a high-performance thermal
control
duct which are designated as sheets are made of corrosion-resistant materials.
Mention may be made here, by way of example, of glass, ceramic, graphite,
:I0 conductive plastics, in particular UV-permeable and resistant plastics,
chrome-nickel
steel, nickel alloys and non-ferrous materials, such as, for example,
aluminum.
In a further preferred embodiment, the depressions in the sheets which are
compo-
vents of a high-performance thermal control duct or flow duct are coated with
a
catalyst, in order to accelerate or promote a reaction taking place in the
flow duct.
Within the scope of the work relating to the present invention, it was found
that, the
greater the longitudinal extent of a depression is in the main flow direction,
along
with a correspondingly small depression width, a depression overlaps and
intersects
with a plurality of depressions of the opposite sheet. This promotes a
reinforced
horizontal mixing action and improves the thermal control process.
Consequently, no
temperature gradients occur in the material stream to be thermally controlled.
To achieve this effect, a height/width ratio of the depression in the sheets
of greater
than l, preferably greater than 5 and particularly preferably greater than 10
is
selected.
The height taken into account in the formation of the height/width ratio
corresponds
to the inner width of the flat duct. The width of the depression corresponds
to the
depression extent in the main flow direction or duct length.
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The present invention therefore relates to high-performance thermal control
ducts, in
which each depression of an individual layer intersects or overlaps with at
least 3
depressions of the opposite layer or holes of the holed sheet, preferably
intersects or
overlaps with more than fave depressions or holes and particularly preferably
with
more than ten depressions or holes of the opposite depression row of the
second layer
or holed sheet.
Within the scope of the present invention, it was found, surprisingly, that
the
formation of a large height of a depression scarcely weakens the earner sheet
in
~Z 0 terms of the compressive load which occurs. The firmer product-side ribs
between the
depressions stabilize the carrier sheet with regard to high differential
pressures and
serve as reinforcing ribs, so that there is a stiffening which withstands a
high
compressive load and no other supports are necessary for the high-performance
thermal control duct.
By virtue of different wall thicknesses towards the heating or cooling side,
the heat
transfer capacity rises, since a locally smaller wall thickness has a lower
heat transfer
resistance. The edge regions between the depressions lie next to one another,
also
designated as reinforcing ribs, have a higher heat transfer resistance by
virtue of the
material thickness towards the thermal control space, so that a medium heat
transfer
resistance must be expected between the full carrier-sheet thickness and the
smallest
sheet thickness.
The edge regions of the depressions additionally form a heating-surface
enlargement,
so that the efficiency of the high-performance thermal control duct is
increased.
In fluidic terms, the medium to be thermally controlled is swirled upon inflow
into
the flow cross-section of the duct having depressions and the heat transfer
capacity is
increased. In particular, the sharp-edged transitions on the edges of the
depressions
provide additional accelerator stall accompanied by turbulence.
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The invention therefore relates preferably to high-performance thermal control
ducts,
in which the depressions in the sheets have a height of up to 90%, preferably
of
greater than 10% to lower than 70%, and particularly preferably of greater
than 10%
to lower than 60% of the sheet thickness.
Within the scope of the present invention, it was found that the angle a.
(Fig. 1), in
conjunction with the height/width retie, determines the overlap and intersect
fre-
quency of the depressions located opposite one another and influences the
differential
pressure of the flow duct which occurs at a constant fluid velocity. The
smaller than
:10 angle oc is in the case of a constant height/width ratio, the lower is the
pressure loss.
The present invention therefare relates preferably to high-performance thermal
control ducts, in which the geometric longitudinal axis of the depressions in
the
sheets is at a preferred angle o~ of 20 to 70 degrees and particularly
preferably at an
:l5 angle of 40 to 50 degrees to the depression row or to the overall flow
direction.
Within the scope of the present invention, it was found that, by virtue of the
large
heat-transfer surface, in combination with a low hold-up, only a small length
of the
high-performance thermal control duct is required in order to achieve
virtually
20 complete temperature equalization between the heat transfer medium and the
product
stream. It is particularly advantageous to use the high-performance thermal
control
ducts according to the invention when there are only small temperature
differences
between the heat transfer medium and the product being heated or cooled.
25 The invention therefore relates preferably to high-performance thermal
control ducts,
in which the depression row of a sheet or of a layer has fewer than 1,000
depressions,
preferably fewer than 500 depressions and particularly preferably fewer than
250
depressions.
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Within the scope of the present invention, it was found that flow ducts with a
substantially lower pressure loss are obtained when these consist of three
sheets with
at least one or optionally further intermediate sheets with holes.
In this case, there are inserted between two sheets with depressions
introduced on
one side, which are also referred to as outer sheets, one or more additional
sheets
with one or more rows of hales, with a geometry identical to or, if
appropriate,
different from the depressions of the lateral sheets, but without exceeding
the width
range of the depression rows.
~0
The invention relates to flow ducts consisting of two sheets with depression
rows
introduced on one side and of at least one sheet inserted between these two
sheets
and having one or more rows of holes which do not exceed the width range of
the
depression rows, so that a flow duct consisting ,of at least three
sheets/layers is
obtained, which has a substantially reduced pressure loss.
The holed sheet inserted senses as an additional turbulence generator, reduces
the
pressure loss for a constant volume flow and does not generate any additional
gaps in
the soldered state.
zo
The holed sheets employed are usually welded or soldered to the adjacent outer
sheets with depressions. Holed sheets can also be employed as detachable
turbulence-producing means in high-performance thermal control ducts.
z5 The holed sheets can have different orifices (c~ Figs. 9 to 9d), so that in
the sheet-
parting planes the areas of the orifices and depressions can have identical
and/or
different geometries. The choice of the geometry to be used for a high-
performance
thermal control duct depends on the thermal control problem concerned.
30 The orifices in these holed sheets are obtained by means of punching
methods,
etching methods or drop-erosion methods.
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According to the invention, depressions can be pressed into the sheet by means
of an
embossing or drop-forging method, with the layer thickness being maintained.
These
are methods of forming technology. The depressions are preferably in the form
of
grooves with a semicircular cross section (Fig. 4, Fig. 4a, Fig. 4b).
The surface of the depressions in the sheets may be of different geometry and
can be
adapted or optimized to the substances to be thermally controlled (Fig. 3,
Fig. 3a,
Fig. 3b, Fig. 3c). The examples shown are merely illustrative, but not
limiting.
,I 0
The workpieces, designated as sheets, are welded to one another, for example
parallel
to the depression rows, along the longitudinal edges. Preferred welding
methods are
TIG (Inert-Gas Welding), laser, EB (Electron-Beam Welding) or rolled-seam
welding.
In a preferred embodiment of the high-performance thermal control ducts,
depres-
sions for receiving a solder are provided in the edge regions of the carrier
sheets, the
depressions performing the function of a solder repository. The depressions
receiving
the solder are connected to one another by means of ducts or grooves, so that
homogeneous soldering can take place. The solder repositories are smaller than
the
product-touched depressions (Fig. 5).
The ducts or grooves for receiving the solder may be positioned in such a way
that a
gap-free high-performance thermal control duct is obtained after soldering.
The gap-
free version is particularly advantageous for applications in the food,
pharmaceutical
and bio-engineering industry.
According to the invention, two sheets lying against one another, with
introduced
depressions, and a holed sheet in between form a closed product-carrying flow
duct
with a high heat transmission capacity, the high-performance thermal control
duct
according to the invention. It may happen, in this regard, that the outer
thermal
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control surface of the three-layer system is too small, so that the outer
sides facing
away from the product may likewise be provided with depressions for the
formation
of thermal control ribs. This appreciably enlarges the outer heat transfer
surface.
When the high-performance thermal control ducts according to the invention are
used
as coolers and the cooling medium is, for example, air, the outer cooling
surface of
the high-performance thermal control duct may then be provided with cooling
ribs
which, if appropriate, are also soldered t;o the duct.
The high-performance thermal control ducts according to the invention, formed
from
at least two sheets with depression rows located ~on one side of each and a
holed
sheet, may be combined with known flow ducts, such as, for example, simple
tubes
equipped with known static mixers, or, for example, with what are known as
profile
tubes having turbulence inserts or flat ducts.
These are eminently suitable as flow reactors for carrying out chemical
reactions.
A plurality of parallel-arranged high-performance thermal control ducts
according to
the invention, comprising in each case three sealingly welded or soldered
sheets/-
layers with inner structures and holes, the structures being depressions or
forming
depression rows, may simultaneously receive an inflow and form a duct-bundle
heat
exchanger or a plate-duct heat exchanger (Fig. 7).
High-performance thermal control ducts layered one above another and in each
case
arranged so as to be offset at 90° to one another may form a cross-
current heat
exchanger. In the cross-current heat exchanger, high-performance thermal
control
ducts with a low hold-up and a small dwell-time spectrum are used in each case
on
the product side and on the thermal control side, so that intensive
temperature
equalization takes place, along with a small product volume and thermal
control
medium volume (Fig. $).
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It is advantageous, in this case, to use layers with depressions introduced on
both
sides of the outer sheets, in order to minimize the number of layers and to
promote a
compact form of construction. A reduction in pressure loss is achieved in the
case of
the cross-current heat exchanger, when high-performance thermal control ducts
with
an inserted holed sheet are used on the pressure-critical side of the heat
exchanger.
The high-performance thermal control ducts with at least one holed sheet
according
to the invention but even thermal control ducts with no holed sheet may also
be used
in a cross-current heat exchanger and, moreover, are suitable as flow ducts
ao
- in a sterilizer for the sterilization of water or of pharmaceutical or
biological
substances,
- for use in photo-bioreactors for the breeding of microorganisms.
The high-performance theryal control ducts with at least one holed sheet
according
to the invention but even thermal control ducts without holed sheet are
suitable,
furthermore, as miniaturized flow ducts on chips for diagnostic purposes.
Brief description ~f the drawings:
Fig. l: shows a sheet-metal strip with eroded depressions which are posi-
tioned next to one another and are at the angle a to the overall flow
direction (9) through the thermal control duct to be formed with the
strip.
Fig. 1 a: is an illustration of section of Fig. 1, from which it can be seen
that
the lateral surfaces of the depressions, which depressions are them-
selves at the angle oc, and having an angle (3 (inflowing side) or (3'
(outflowing side) to the overall flow direction.
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Fig. 2: shows two sheet-metal strips according to Fig. 1 which are laid one on
the other and form a flat duct for a heat exchanger, the upper sheet
(1') being partially open, so that the outlines of the depressions lying
one above the other can be seen.
Fig.2a: shows section of the flat duct from Fig. 2 with the overall flow
direction (9), with the inner depression rows located opposite one
another.
Fig. 3-3c: show alternative contours of the depressions.
Fig. 4-4b: show cross sections of the depressions.
Fig. 5: shows a sheet-metal strip (i.e., a sheet) which has grooves serving as
soldering repositories in the edge regions.
Fig. 6: shows depression rows with a depression according to Fig. 3 in a flow
duct.
Fig. 7: illustrates a parallel arrangement of high-performance thermal control
ducts with depression rows, which are inserted in a thermally
controlled housing and welded together and which form a duct heat
exchanger.
Fig. 8: shows a sheet-metal strip having grooves on both sides.
Fig. 8a: shows the front of the sheet-metal strip having grooves on both
sides.
Figs. 9-9d: show different types of orifices and orifice arrangements for
holed
sheets.
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Examples
Fig. 1 illustrates a can-ier sheet 1 with depressions 2. The depressions have
a
trapezoidal cross-sectional surface and are worked into the sheet or into the
layer at a
distance from and adjacent to one another and thereby form a depression row
2', 2".
The geometric axis 4 of extent of the depressions is at an angle a,
transversely to the
center axis 5 of the depression row and to the overall flow direction 9. The
depressions of the depression row are formed only partially at the sheet ends
6, 6', so
that inflow orifices 7 and outflow orifices 8 are formed at the ends of the
sheet. The
.10 depression row 2, 2', 2" at the same time defines the main flow direction
9 of the
thermal control duct to be formed. Above and below the depression row as
illustrated
are located narrow edge regions 10 which may be welded or soldered to
corresponding edge regions of a second carrier sheet, in order to produce a
pressure-
tight flow duct with a high thermal control capacity.
In Fig. 1 a, a sectional view of carrier sheet 1 is illustrated. The carrier-
sheet thickness
11 and the depressions 2, the height of which is less than the earner-sheet
thickness,
can be seen. In this version, the depth of depression is 50~/0 of the sheet
thickness. In
the sectional illustration, it can be seen that the lateral surface 3 on the
inflowing side
of the depression has an angle (3' and the surface 3' of the outflowing side
has an
angle (3 in the overall flow direction, so that the flow passes optimally
through the
depression, a vertical mixing action in relation to the opposite depression
row is
assisted and, as a result, product deposits are prevented.
In Fig. 2, two layers or sheets l, I' are laid one on the other, the second
sheet 1'
having been rotated through 180 degrees with respect to the first and lying on
the
lower sheet l, and the upper sheet 1' being opened partially to reveal the
depressions.
What can be seen are the overlapping and intersecting depressions and the
inner webs
which are formed between the depressions and which generate a horizontal
mixing
action, parallel to the longitudinal extent of the depressions, by the
deflection and
division of the main stream. When flow ducts are under a pressure load, the
inner
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webs act at the same time as reinforcing ribs and thereby increase stability
under
pressure.
Fig. 2a illustrates a section of the two-layer duct illustrated in Fig. 2, but
with a
reduced length. It can be seen clearly that the lateral surfaces 3 of the
depressions 2,
the said lateral surfaces being at the angle (3 in the flow direction, assist
a vertical
mixing action and form virtually no regions where the throughflow is
insufficient. It
can be seen, furthermore, that the rib intersection points of the depressions
lie one on
the other only in a punctiform manner and there is no great gap formation in
the
,10 region where throughflow takes place. In this presented version, the ratio
of
depression width to center distance = 1.
Fig. 3 to 3c show various forms of depression surfaces. Fig. 3 shows an
elongate
depression with obliquely set lateral surfaces. Fig. 3a illustrates a form
which can be
produced typically by the drop-erosion method, so that the lateral surfaces of
the
depression which are located in the flow direction are at an angle and the
upper and
lower edge surface of the depression run perpendicularly into the sheet. Fig.
3b
shows a longitudinally extended depression which may be formed by means of a
plurality of countersinking operations. Fig. 3c shows typically a depression
which
has been generated in a chip-removing manner by means of a radius or spherical
milling cutter. It is advantageous, in this form, that the flow passes
efficiently
through all the regions and the dwell-time spectrum is small.
Fig. 4 to 4b show various preferred cross-sectional :forms of depressions, for
example
a trapezoidal version (Fig. 4~, an acute-angled version in the form of a
triangle
(Fig. 4a) and a circle segment (Fig. 4b~ or semicircle. The cross-sectional
form of
Fig. 4b corresponds to the depression surface form from Fig. 3c. It can be
seen from
fig. 3 to 3c and 4 to 4b that depressions form surfaces always conducive to
better
flow routing.
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Fig. 5 shows a portion of a sheet 1 with, for example, longitudinally extended
depressions 2 having the cross-sectional form according to Fig.4 and with a
depression surface corresponding to Fig. 3, a radius being arranged at the
upper and
lower end of the depressions. Above and below the depression row illustrated,
a
groove 12 running parallel to the center axis 5 of the depression row is
provided for
receiving a solder. The groove for receiving the solder may also be adapted to
the
outer contour of the depression row, so that soldering closes all the gaps of
the two
sheets lying one on the other and having depression rows and prevents a
product
deposit. Even in the case of an interposed holed sheet for reducing the flow
loss, all
.10 the gaps in the edge region of the depression row are closed.
Fig. 6 illustrates a flow duct which is formed frorrl two sheets 1, 1' laid
one on the
other and having depressions, in a similar way to what is shown in Fig. 5. It
can be
seen clearly that a fluid is divided in the inflow region along the
throughflow
direction 9 of the duct by virtue of overlapping and intersecting depressions
and is
subsequently combined again. These flow processes produced parallel to the
sheet
width generate a horizontal mixing effect, whilst the lateral surfaces 3, 3'
of the
depressions, the said lateral surfaces being at an angle (3, ensure the
vertical mixing
effect.
Fig. 7 illustrates by way of an example a parallel arrangement of high-
performance
tbermal control ducts 70, through which the flow passes in parallel. The high-
performance thermal control ducts are inserted in an onflow and outflow plate
72,
72' and are welded to this. The onflow plate 72 on the inlet side and the
outflow plate
72' on the outlet side of the product are, in tum, inserted into a housing 71
and
welded. The housing 71, which at the same time forms the thermal control
space, has
a thermal control medium supply connection piece 73 and a thermal control
medium
discharge connection piece 74. A cold transfer medium or a heat transfer
medium can
be fed into the housing 71, in order thermally to control uniformly, quickly
and with
great care the high-performance thermal control ducts and the product 75
flowing
through these. For the better mounting of the heat exchanger in existing
plants,
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connection possibilities, not illustrated here in the diagram, such as, for
example,
flanges or product-side connection pieces, are provided.
Fig. 8 illustrates by way of an example a metal-sheet strip 80 for a thermal
control
duct with grooves 83, 84 on both sides. What can be seen are the inner webs 81
of
the grooves being at the angle (3 in the flow direction. The grooves of the
other side
of the metal-sheet strip are shown by intermittent lines.
Fig. 8a illustrates the front or the inflow or outflow side of a metal-sheet
strip 80.
>10 Fig. 8a clearly shows that because of the grooves 83 and 84 on both sides
of the
metal-sheet strip the sheet itself can become very thin in the area of the
depressions.
Figs. 9 to 9d show different hole patterns and hole arrangements for a
turbulence-
generating holed sheet for the high-performance thermal control duct. The rows
of
1 S holes can be arranged in a single row or ire several rows and the orifices
can be
arranged in parallel or in a staggered fashion, depending on the problem to be
solved.
Care must however be taken not to position in the sheet-parting plane
geometries
which, in relation to the adjacent sheet with depressions, have equally sized
areas or
are of the same type or point in the same direction.
