Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Description
Device for Freezing and/or Cooling-Down Products
The invention relates a device for freezing and/or cooling-
down products comprising a cooling chamber, which encompasses
a transport device for conveying the products through the
cooling chamber, at least one device for generating a cold
gas atmosphere for the cooling chamber and an extraction
device for the cold gas as well as at least one axially
conveying ventilator for conveying the cold gas. A use of
this device is furthermore the object of the instant
invention.
A series of devices and methods is known for cooling-down
products, wherein cooling-down is to refer to herein as to
cooling as well as to freezing and deep freezing. Cooling
tunnels and spiral freezers, for example, can be listed as
state of the art, in the case of which products are in each
case transported through the device and are cooled-down by
means of the contact with cryogenic gases. Cryogenic gases in
liquid and/or gaseous state are often used for this purpose.
The use of liquid nitrogen or liquid carbon dioxide is well
known.
Conventionally, the liquid nitrogen, e.g., is guided through
a heat exchanger and is expanded by means of a throttling
valve as expansion device, so as to then be introduced into a
cooling tunnel. There, the expanded gas accommodates heat
from the products, which are to be cooled-down. The gas,
which is heated through this, leaves the cooling tunnel as
abstracted gas. To impact the flow through the device, an
extraction device is typically used, which extracts the
heated gas from the cooling tunnel by means of extraction.
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Ventilators, for the most part axially conveying ventilators,
are furthermore used to improve the flow and to increase the
convective heat transfer.
It is the object of the instant invention to provide a device
for freezing and/or cooling down, which is improved as
compared to the state of the art.
The posed object is solved in that the axis of the at least
one ventilator is attached at an angle to the vertical,
wherein the vertical to the moving direction of the products
serves as reference direction and the at least one ventilator
is attached to the ceiling of the cooling chamber, wherein
the axis of the ventilator includes an angle b with a vector,
which represents the moving direction of the products,
wherein the origin of the vector is placed at the lower end
of the axis. The deviation of the axis of the ventilator as
compared to embodiments, which typically extend vertically
downwards, provides for a specific impacting of the fluid
flow of the cold gas through the cooling chamber. The
embodiment of a directed fluid flow or agitation of the cold
gas is thus preferably made possibly, whereby the convective
heat transfer between cold gas and product can be increased
considerably with particular advantage. In individual cases,
it can also be advantageous to attain a non-directed fluid
flow, which is also possible by means of the instant
invention.
Contrary thereto, the cold gas atmosphere in the case of a
common ventilator axis, which extends vertically downwards,
is pressed centrally downwards only in the area of the
ventilator and rises again directly next thereto. This
movement of the cold gas does not represent an embodiment of
a fluid flow in terms of the invention, because the cold gas
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does not leave the close-up range of the ventilator thereby.
In the case of devices comprising commonly attached
ventilators, the embodiment of a cold gas fluid flow is only
possible via the use of an extraction device.
In the case of the afore-used wording, a moving direction of
the products in the horizontal is assumed. In the event that
the moving direction of the products deviates from the
horizontal, vertical in terms of the invention can also refer
to vertical to the moving direction. In the case of a
conveyor belt as transport device, e.g., which rises relative
to the horizontal, this leads to the correct positioning for
the axis of the ventilator according to the instant
invention.
As a rule, axially conveying ventilators are equipped with
rotor blades comprising a curved profile. The preferred fluid
flow direction for the cold gas is opposite to the moving
direction of the products, which are moved by means of the
transport device, thus in counter flow. For certain
applications, however, the reverse, thus the fluid flow
direction of cold gas parallel to and in the moving direction
of the products, which are to be cooled-down and/or frozen
(coflow), can be more advantageous.
Preferably, the angle b between the axis and the vector is
smaller than 900, thus acute angled. In the case of
counterflow equipment, the fluid flow of the cold gas is
supported by means of this arrangement. In the case of the
coflow, this arrangement has a delaying or slow-down effect,
respectively, on the fluid flow of the cod gas. The relative
dwell time of a certain quantity of cold gas in the range of
a certain quantity of product, which is to be cooled-down,
can thus be varied via the selection, which is made for the
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arrangement. Different cool-down characteristics can thus be
realized, that is, the speed of the cool-down process can
thus be adjusted, that is, by how many degrees ( C) the
temperature of a product decreases in a certain period of
time.
According to another advantageous embodiment of the instant
invention the angle b between the axis and the vector is
greater than 90 , thus obtuse angled. In the case of this
embodiment, the fluid flow of the cold gas is slowed down in
the case of counterflow equipment. In the case of a coflow
arrangement, the fluid flow of the cold gas is accelerated,
thus supported through this. The possibilities to impact the
cool-down process in a device according to the invention
through this are the same as already described in the
preceding paragraph.
Advantageously, the angle a, which the axis of the ventilator
draws with the vertical, lies in the range of from 10 to 8 ,
preferably in the range of from 10 to 5 . As was already
described with the information, which was provided with
reference to angle b, the axis can thereby be deflected in or
against the moving direction of the products. Both
alternatives are to be covered herein by means of the afore-
claimed area for the angle a.
In the case of more than one ventilator, all of the axes can
encompass the same inclination (deviation from the vertical).
However, it is also possible, for preparing a course for the
fluid flow characteristic, to individually select the
inclination of an axis in each case and to attach this axis
accordingly.
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According to an advantageous development of the invention,
provision is made for a device for injecting cold gas.
Advantageously, provision is made for a cold gas reservoir,
in particular for a cold gas reservoir for liquefied cold
gas. In the case of such an embodiment, the cooling medium,
e.g., which is removed from the cold gas reservoir under a
first higher pressure (e.g. approx. 3.5 bar for nitrogen;
e.g. approx. 15 bar for carbon dioxide), is fed to an
expansion device and is expanded to ambient pressure. The
temperature of the cooling medium decreases through this. The
cold gas flow generated in that way is supplied into the
space for accommodating the products, which are to be cooled
down, e.g. to the interior of a cryogenic cooling tunnel, and
is used at that location for cooling-down the products.
In a particularly advantageous manner, provision is made for
liquid nitrogen and/or for liquid carbon dioxide for
generating the cold gas.
The object of the instant invention is furthermore solved by
the use of the device according to one of claims 1 to 7 for
freezing and/or cooling-down foods. The instant invention is
particularly interesting for sensitive products, which are to
be cooled-down, such as foods or pharmaceuticals, for
example, because it is particularly advantageous in the case
of these products to be able to influence the cool-down
characteristics in the described manner.
The invention provides a series of further advantages, only a
few of which will be mentioned below in an exemplary manner:
By specifically embodying a cold gas fluid flow by means of
the ventilators, the convective heat transfer between cold
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gas and product, which is to be cooled, can be increased in
an advantageous manner. It would not be possible to reach
this goal by means of the extraction capacity of the
extraction device or it would not be possible to reach an
increase thereof, because it would thereby not be possible to
adjust the length of dwell time of the cold gas in the
cooling tunnel independent on the extraction capacity.
However, the instant invention provides for a further
adjusting possibility, which makes it possible to choose the
dwell time in certain limits independent on the extraction
capacity.
Expensive and extensive reconstruction is not necessary for
existing equipment. Only the attachment of the ventilator or
of the ventilators to the ceiling of the cooling chamber must
be modified so as to provide for a suitable attachment.
Existing equipment can be upgraded and converted by means of
the invention. The already available equipment parts can
thereby be reused for the most part. Contrary to conventional
methods, an additional energy yield is possible by means of
the invention.
The invention as well as further embodiments of the invention
will be defined in more detailed below by means of the
exemplary embodiment, which are illustrated in the figures.
Figure 1 shows a freezing tunnel (overview)
according to the invention,
Figures 2 to 5 show schematic illustrations of different
inclination possibilities for the axis of
a ventilator according to the invention.
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Figure 1 shows a freezing tunnel comprising all of the
substantial components as overview. The inclination of the
axes of the ventilators cannot be seen in detail in this
illustration, because the deviation is very small. In Figures
2 to 5, this deviation is illustrated in an exaggerated
manner, which first makes it visible. The freezing tunnel
thus encompasses a cooling chamber 1 and a transport device
2, on which the products 6, which are to be cooled-down,
rest, and by means of which these products are transported
through the cooling chamber, namely from left to right in
this example. The fluid flow of the cold gas, which escapes
from the device 3 for generating a cold gas atmosphere, which
is sprayed onto the products 6 or which acts upon the
products 6 in the area of the device 3, respectively, is
oriented in this example opposite to the transport direction
of the products. The cold gas thus flows herein from right to
left through the cooling chamber 1. The fluid flow is
supported by two ventilators 4, the axes 5 of which are
deflected out of the vertical such that the angle b between
the axis 5 and the vector, which represents the moving
direction of the products 6, is in each case smaller than
900, thus acute angled. The fluid flow is supported through
this, is thus accelerated as compared to a device comprising
ventilators, which are conventionally attached vertically.
Both of the areas A and B illustrated in Figure 1 can be
characterized as precooling area A and as cooling area B.
Figure 2 shows an angle b between the axis 5 and the vector
of less than 90 , thus acute angled. In the case of
counterflow equipment, the fluid flow of the cold gas is
supported by means of this arrangement.
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The fluid flow direction of the cold gas is indicated in
Figures 2 to 5 in each case by means of a dashed arrow.
Figure 3 shows the acute angled arrangement in the case of
the coflow, in which said arrangement has a delaying or slow-
down effect on the flow of the cold gas, respectively.
Figure 4 shows another advantageous embodiment of the instant
invention, in the case of which the angle b between the axis
and the vector is greater than 90 , thus obtuse angled. In
the case of this embodiment, the fluid flow of the cold gas
is slowed down in the case of a counterflow arrangement.
Figure 5 shows the obtuse angled arrangement for the case of
a coflow arrangement. The fluid flow of the cold gas is
accelerated through this, is thus supported.
The relative dwell time of a certain quantity of cold gas in
the area of a certain quantity of product, which is to be
cooled-down, can thus be varied via the selection, which is
made for the arrangement. Different cool-down characteristics
can thus be realized, that is, the speed of the cool-down
process can thus be adjusted, that is, by how many degrees
( C) the temperature of a product decreases in a certain
period of time. The extraction capacity of the extraction
device 7 (see Fig. 1) can thereby be held so as to be
constant in an advantageous manner.
