U.S. patent application number 14/349908 was filed with the patent office on 2015-01-29 for system to improve icing problems in blast freezer tunnels.
The applicant listed for this patent is Thierry Dubreuil, Didier Pathier. Invention is credited to Thierry Dubreuil, Didier Pathier.
Application Number | 20150027140 14/349908 |
Document ID | / |
Family ID | 46889352 |
Filed Date | 2015-01-29 |
United States Patent
Application |
20150027140 |
Kind Code |
A1 |
Dubreuil; Thierry ; et
al. |
January 29, 2015 |
System to Improve Icing Problems in Blast Freezer Tunnels
Abstract
A method and device for chilling food products by jets blasted
into a tunnel, said tunnel comprising/a conveyor for conveying
products into a tunnel, at least one plate, located opposite the
conveyor, and provided with through holes, the plate or plates
being located above and/or below the conveyor; and at least one
means of blowing a cold fluid through the through holes and towards
the products, characterized in that, during all or part of the
periods of operation of the tunnel and/or during all or part of the
periods of stoppage of the tunnel, there takes place an operation
to clear all or part of said through holes, using a network of
channels allowing a blow gas to be distributed opposite all of said
through holes.
Inventors: |
Dubreuil; Thierry;
(Boissets, FR) ; Pathier; Didier; (Voisins Le
Bretonneux, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dubreuil; Thierry
Pathier; Didier |
Boissets
Voisins Le Bretonneux |
|
FR
FR |
|
|
Family ID: |
46889352 |
Appl. No.: |
14/349908 |
Filed: |
September 4, 2012 |
PCT Filed: |
September 4, 2012 |
PCT NO: |
PCT/FR2012/051976 |
371 Date: |
September 8, 2014 |
Current U.S.
Class: |
62/63 ;
62/380 |
Current CPC
Class: |
F25D 25/04 20130101;
F25D 3/11 20130101; F25D 13/067 20130101; F25D 31/00 20130101; A23L
3/36 20130101; A23L 3/361 20130101 |
Class at
Publication: |
62/63 ;
62/380 |
International
Class: |
F25D 31/00 20060101
F25D031/00; F25D 25/04 20060101 F25D025/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 5, 2011 |
FR |
1158990 |
Claims
1-3. (canceled)
4. A device for cooling food products by impacting jets comprising
a tunnel that comprises a conveyor adapted to convey the food
products in the tunnel at least one plate, situated facing the
conveyor, and provided with a plurality of orifices traversing
through the at least one plate, the at least one plate being
situated above and/or below the conveyor; and at least one blowing
system adapted to blow a cold fluid through the plurality of
traversing orifices and towards the food products, the device
comprising a network of channels for distributing a blow gas above
a top plate that is provided with the plurality of orifices
traversing through the top plate and/or below a bottom plate that
is provided with the plurality of orifices traversing through the
bottom plate, one or more of the channels being provided with
injection orifices or injection tubes, the positioning of which is
adapted to direct the blow gas towards the plurality of orifices
traversing through the top and/or the bottom plate, in order to
simultaneously clear two or more of the plurality of orifices
traversing through the top and/or the bottom plate.
5. The device of claim 4, wherein the plate or plates are in the
form of a corrugated stainless sheet in the form of successive Vs,
each V being provided with a row of traversing orifices, and in
that the network of channels comprises at least one service tube,
associated with each plate, closed at one of the ends thereof,
housing one of the ends of the Vs, and in that the device
comprises, facing each V, an injector connected to the service tube
and adapted to inject the blow gas into the V corresponding
thereto.
6. A method for cooling food products by jets blasting in a tunnel
that comprises device for cooling food products by impacting jets
comprising a tunnel that comprises a conveyor adapted to convey the
food products in the tunnel at least one plate, situated facing the
conveyor, and provided with a plurality of orifices traversing
through the at least one plate, the at least one plate being
situated above and/or below the conveyor; and at least one blowing
system adapted to blow a cold fluid through the plurality of
traversing orifices and towards the food products, the device
comprising a network of channels for distributing a blow gas above
a top plate that is provided with the plurality of orifices
traversing through the top plate and/or below a bottom plate that
is provided with the plurality of orifices traversing through the
bottom plate, one or more of the channels being provided with
injection orifices or injection tubes, the positioning of which is
adapted to direct the blow gas towards the plurality of orifices
traversing through the top and/or the bottom plate, in order to
simultaneously clear two or more of the plurality of orifices
traversing through the top and/or the bottom plate, wherein the
method comprises the step of injecting the blow gas through the
plurality of traversing orifices, at least one of the traversing
orifices having a frost accumulation, to thereby reduce or
eliminate the frost accumulation.
Description
[0001] The present invention concerns the field of methods for
chilling food products in apparatus of the tunnel type, using
direct or indirect injections of a cryogenic fluid such as liquid
nitrogen.
[0002] Traditionally, such tunnels comprise: [0003] an insulated
chamber provided with an entry and an exit; [0004] means for
conveying products between the entry and the exit; [0005] means for
bringing a cryogenic liquid into the chamber to enable the products
to be put in contact directly with this liquid (usually, these feed
means comprise manifolds for spraying liquid onto the products) or
indirectly through the fact that the cryogen is injected into
exchangers internal to the tunnels (usually referred to in this art
as "cold batteries"), the transfer of the cold to the products
being effected by an exchange with the internal air of the tunnel
through the action of ventilation means associated with each
battery; [0006] and ventilation means, able to blow cold gas onto
the passing products.
[0007] The food industry is continuously seeking equipment that is
more and more efficient economically and in particular more and
more compact (using the least surface area on the ground). In many
cases this makes it possible to increase the production capacity of
a given site without investing in new buildings. Recent freezer
tunnels thus offer more and more elaborate techniques for
increasing the production capacities whilst reducing the footprint
of the equipment.
[0008] To do this, recent high-performance equipment must increase
the coefficient of heat transfer with the product to be frozen. In
the case where cold-gas ventilation is used to transfer the cold
from the cold source to the product, a common technique consists of
increasing the velocity of this cold gas. The cold gas is then
pressurised and injected in the form of jets impacting directly on
the product ("impingement" is often spoken of this industry). The
heat transfer coefficient is then very high and the refrigerating
capacity of the machine per unit surface area is also very high.
The document EP 1 449 443 A1 illustrates this impaction prior
art.
[0009] This very interesting technique does however have drawbacks
and technical difficulties. The ventilation power is often
difficult to control especially after several hours of production,
when the characteristics of the ventilation system have been
modified by contamination thereof (frost or other deposit).
[0010] Moreover, the air flow and the ventilation velocities are
very high, and asymmetry in the distribution of the cold gas is
observed, which causes entries of air on one side of the equipment
and exits of air on the other side.
[0011] It has been demonstrated that the frost results mainly from
infiltrations of outside air. These infiltrations of air from the
production room into the freezer tunnel are of course accompanied
by an entry of water vapour (moisture from the air) that will be
deposited in the form of frost inside the machine. Thus this poor
control of the equilibrium of gases causes not only an
overconsumption of refrigeration and an additional production cost
but also accelerated contamination of the system for ventilating
the plates producing the blast jets and possibly the exchangers
installed, which causes self-amplification of the phenomenon.
[0012] Various solutions have been proposed in the literature for
improving this excessive-frosting situation by limiting the air
inlets and in particular: [0013] the establishment of buffer zones
at the tunnel entry/exit: this solution sets out to combat one of
the phenomena observed in such tunnels where, when the jets impact
at high speed on the sole plate, some of the cold air is expelled
out of the tunnel, the quantity of air in the tunnel being
constant, this automatically creates infiltrations of warm air. The
area where the products are loaded into the tunnel then acts as a
"tube" that guides the air flow but does not significantly reduce
infiltrations of air.
[0014] Then one (or more) buffer areas are positioned, immediately
downstream of the loading area in one case and immediately upstream
of the tunnel exit in the second case, buffer zones that are not
ventilated, through enlargements of the external shell of the
tunnel (from 50 cm to 1.5 m for each zone at the entry and exit of
the freezer), thus creating on each side a dead space that dampens
the gas velocities, which naturally reduces the entries of air and
exits of cold gases. However, this system has a major drawback,
which is increasing the overall size of the machine, which runs
counter to the effect sought initially by the adoption of the blast
jets. [0015] the use of physical curtains: this solution consists
of placing plastic or stainless steel curtains at the entry/exit of
the apparatus. These curtains in fact limit the entries of air and
the exits of cold gases. However, while they are more effective,
they consequently block the entries to the freezer. In practice,
they are often little effective since, being situated on the
product passage, they cannot really close off the entries/exits. In
addition, they sometimes pose hygiene problems when they touch the
passing products. [0016] the use of gaseous curtains: this solution
consists of installing, at the tunnel entry and exit, a system for
blowing air intended to compensate for the imbalance in the tunnel.
This system may sometimes give satisfactory results when the
imbalance is very small but on the other hand, when it is a case of
compensating for average to high imbalance, this system has not yet
shown its ability to re-establish equilibrium of the cold
gases.
[0017] Nevertheless, in this food industry, it is necessary to bear
in mind the fact that one of the origins of the entries of moisture
is also related to the evaporation of some of the water contained
in the incoming product itself, and particularly certain incoming
products. Thus the frost appears more or less rapidly at the blast
orifices but it always appears, and the flow rate of injected gas
decreases over time just like the thermal efficiency of the
machine.
[0018] It is then known that other types of solution have been
proposed in the literature, and in particular: [0019] adding a
vibration source on the plates that support the orifices. If the
vibrations are sufficiently powerful to detach the frost, this
technique may prove to be advantageous.
[0020] However, these powerful vibrations do in themselves present
several drawbacks: they weaken the machine (the welds, the chassis,
but also the electrical components such as motors, temperature
probe, sensors, etc.). It must also be mentioned that the system
generating vibrations may have insufficient reliability when it
operates in a very cold environment, and in addition the cost of
the system is fairly high. [0021] the solution that consists of
creating overpressures from time to time in the system supplying
the orifices. This overpressure is capable of removing from the
orifices the frost that encumbers them if the pressure is
sufficiently high. The drawback of this technique is the cost
thereof: this is because it requires the use of an oversized
ventilation system capable of temporarily delivering high power.
[0022] the use of an electrical system for locally heating the
orifices, but such use proves in practice to be very difficult.
[0023] It will therefore be understood that, in order to preserve a
good level of heat exchange in this type of machine, it would be
advantageous to be able to leave the blast orifices clear without
needing to stop or heat the machine.
[0024] As will be seen in more detail hereinafter, the present
invention sets out to propose a novel solution for preventing the
clogging by formation of frost at the orifices forming the blast
jets, without the use of a mechanical vibration or heating, through
a system for distributing a blow gas (for example air) that is well
designed and sized.
[0025] To this end, the invention proposes a device for cooling
food products by blast jets comprising a tunnel that comprises:
[0026] a conveyor for the products in the tunnel [0027] at least
one plate, situated facing (above and/or below) the conveyor, and
provided with through orifices, [0028] and at least one means for
blowing a cold fluid by blasting through traversing orifices and
towards the products,
[0029] the device comprising a network of channels for distributing
a blow gas above the top plate and/or below the bottom plate,
provided with through orifices, all or some of the channels being
provided with injection orifices or injection tubes, the
positioning of which in the network directs blow gas towards the
through orifices in the plate or plates, in order to simultaneously
clear all or some of these through orifices.
[0030] As will have been understood from a reading of the above,
the blowing is thus effected on the side where the frost
accumulates: this is because in practice, in such a blast tunnel,
the frost accumulates above the top plate and below the bottom
plate (the one situated under the conveyor as projecting cold gas
upwards in order to impact on the bottom face of the products),
that is to say the blowing thus takes place on the side of the
arrival of the cold gases in the system (rather than on the side
where the blast jets emerge).
[0031] Though it can be envisaged according to the invention
clearing some of the orifices (for example 80% to 90% of these
orifices), it will be preferred to position a blowing network
making it possible to clear all the through orifices.
[0032] In the device of the invention, the plate or plates provided
with through orifices are advantageously made from food-quality
stainless steel. These plates are removable so as to facilitate
cleaning thereof after operation.
[0033] In this industry plates of very varied forms are
encountered, and in particular these may be planar or in a V shape
or corrugated.
[0034] For purely illustrative purposes, the through orifices in
the plate may also be of varied forms and in particular in the form
of cylinders, circles, slots, optionally beveled (individual ones
distributed along the plates or several slots distributed over the
length of the plate, each slot occupying almost all the width of
the plate), or cones with beveled or rounded edges.
[0035] Usually but non-limitatively, the fluid-blowing means is a
centrifugal fan driven by a motor.
[0036] Likewise, the tunnel may use pairs of plates, a top plate
and a bottom plate, situated in parallel on either side of the
conveyor, at least one, and preferably both, being provided with
through orifices.
[0037] The invention also concerns a method for cooling food
products by blast jets in a tunnel, a tunnel that comprises: [0038]
a conveyor for the products in the tunnel [0039] at least one
plate, situated opposite the conveyor, and provided with through
orifices, the plate or plates being situated above and/or below the
conveyor; [0040] and at least one means for blowing a cold fluid
through the through orifices and towards the products,
[0041] the method being characterised in that, throughout all or
some of the operating periods of the tunnel and/or during all or
some of the stoppage periods of the tunnel, an operation is carried
out of clearing all or some of said through orifices, in the
following manner: [0042] a network of channels is available for
distributing a blow gas above a top plate and/or below a bottom
plate that is provided with through orifices, all or some of the
channels being provided with injection orifices or injection tubes,
the position of which in the network makes it possible to direct
blow gas towards the through orifices in the plate or plates,
[0043] said network of channels is fed with blow gas in order to
simultaneously clear all or some but preferably all said through
orifices.
[0044] The accompanying FIG. 1, in the various views (a), b), c)
etc.) thereof illustrates, by means of schematic partial
representations, an embodiment of the invention where: [0045] the
impacting plate is in the form of a corrugated stainless steel
sheet in the form of successive Vs, each V being provided with a
row of slots/orifices, optionally beveled; [0046] FIG. 1a) displays
the structure of the plate with 7 Vs and the blowing device, in
exploded mode for better reading (the right-hand view in this FIG.
1a) provides the detail of a V); [0047] FIG. 1b) displays the plate
and the blowing device in assembled mode; [0048] FIG. 1c) displays
a situation where the through orifices are obstructed by frost;
[0049] while FIG. 1d) displays the effect of the arrival of a jet
of compressed air in each V making it possible to clear each
through orifice (here once again the right-hand view provides the
detail of a V); [0050] as can be seen clearly in these figures, for
this embodiment there is a service tube, closed at one of the ends
thereof, with a diameter of around 40 mm, that runs along the end
of the Vs on one side of the plate, and facing each V there is a
small injector or tube connected to the service tube (here with an
inside diameter of around 2 to 5 mm) that injects compressed air in
the V. The injected air will therefore first of all touch the first
orifice and clear it, then the second, then the third, etc. Thus an
injector unblocks a line of several orifices over a distance of
approximately 200 to 600 mm depending on the pressure and flow rate
of air injected. [0051] when injection is demanded (as has been
seen, whether this be during a production phase of the tunnel or
during a period where it is stopped, and whether this be on
isolated command by an operator or at pre-programmed regular
intervals, or on the instruction of an automatic controller
following the reception of information representing a blocked state
of the orifices, for example a pressure measurement in the
ventilation) the accumulation of frost situated facing each
injection tube is swept by the power of the air jet, the detached
frost is carried away by the air flow, and the tunnel can continue
to operate normally. [0052] the injections of blow gas may be very
short because of the pressures envisaged (typically a few seconds,
for example between 0.2 and 2 seconds).
[0053] The consumption of compressed air may be optimised by
spacing the injections apart as far as possible while preserving
satisfactory thermal efficiency of the machine between the
injections.
[0054] In order to limit the number of compressed air injectors,
the orifices are aligned and the injection of compressed air is
arranged so that it impacts a line of several orifices.
[0055] As seen above, for this embodiment, a single service tube is
installed disposed on one side of the plate, but obviously it is
clearly possible to envisage, depending in particular on the size
of the impacting plate, to use several service tubes, one on each
side of the plate, and blowing then takes place in the two opposite
directions.
[0056] Even larger plates that would require more than two service
tubes (one at each end and one for example at the middle of the
plate) are sufficiently rare not to dwell here on this
situation.
[0057] FIG. 2 illustrates by means of a partial schematic
representation a variant embodiment of the service tube of FIG. 1,
supplying each V of the impacting plate.
* * * * *