Apparatus for the thermal treatment of food products and process for the thermal treatment of food products

Technical Field

The present invention falls within the food industry.

In particular, the invention relates to an apparatus for the thermal treatment of food products capable of adjusting the temperature and humidity of the products during the treatment. Preferably, such an apparatus for the thermal treatment is a tunnel-shaped refrigerator.

In addition, the invention relates to a process for the thermal treatment of food products.

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Prior Art

In the confectionery and bakery industry, it is known to use specific machines for the thermal treatment of food products following the cooking step. Some examples are given in the following documents: US2002/139006, CN107660623, US4665627, CN108273791 .

Generally, a machine for the thermal treatment comprises at least one conveyor belt for the movement of the food products between the cooking step and the preservation step. During the transportation on the conveyor belt, the food products undergo a cooling, perhaps assisted by fans or similar elements.

Currently, the surface dimensions of the machines for the thermal treatment are determined by the length of the conveyor belts necessary to obtain an optimal cooling, generally varying between 350 metres and 500 metres. Although the length is high, it is essential in order to perform a proper cooling of the food products.

Sometimes, industrial warehouses do not have a sufficient surface extension to hold the machines for the thermal treatment, whereby the conveyor belts, in order to reduce their dimensions, can extend along both a horizontal and vertical path (ascending and/or descending circle) forming what are commonly referred to as cooling towers. While solving the problem of dimensions, the cooling towers have the disadvantage of allowing difficult access to an operator who must carry out checks on the food products or must carry out ordinary maintenance.

In addition, it must be considered that the food products to be thermally treated can have different dimensions and that, in the case of products of relatively large dimensions, the length of the conveyor belts may not be sufficient to ensure proper cooling. In this case, the moisture formed with the cooking step is not sufficiently reduced and an amount of free water remains within the food product, the so-called "Water Activity" phenomenon.

This phenomenon reduces the quality of the product and can lead to mould and the proliferation of potentially dangerous bacterial flora if ingested.

There have been attempts to solve the aforesaid drawbacks by increasing the number of fans installed along the conveyor belt. However, it has been found that the increase in the flow of cold air conveyed on the food products is not only unable to reduce the level of humidity until obtaining the optimum value (usually equal to 22%), but instead tends to frost and thus only delays the aforementioned "Water Activity” phenomenon.

Aims of the invention

In this context, the technical task of the present invention is to propose an apparatus for the thermal treatment of food products which obviates the drawbacks of the known art as mentioned above.

In particular, an object of the present invention is to provide an apparatus for the thermal treatment of food products, which is able to extend for a considerably reduced extension compared to the prior art so as to occupy a minimum surface of the warehouse in which it is arranged. In addition, the apparatus intends to eliminate the need to use cooling towers so as to present a simplified structure that is easily accessible for an operator.

Another object of the present invention is to provide an apparatus for the thermal treatment of food products capable of efficiently controlling the temperature and humidity levels of the food products as a function of the requirements and the food product itself.

A further object of the present invention is to provide an apparatus for the thermal treatment of food products able to maintain the positioning of the food products constant for the entire duration of the thermal treatment so that any devices outside the apparatus (e.g. machinery for the filling or for the topping of the confectionery products), pre-configured to act on the products, find the latter in the optimal position for the processing.

The stated technical task and specified objects are substantially reached by an apparatus for the thermal treatment of food products and by a relative process for the thermal treatment of food products, which comprise the technical features disclosed in the independent claims. The dependent claims correspond to further advantageous aspects of the invention.

It should be highlighted that this summary introduces, in simplified form, a selection of concepts which will be further elaborated in the detailed description given below.

The invention relates to an apparatus for the thermal treatment of food products, which comprises a box-shaped body which extends along a longitudinal direction between a first divider and a second divider for a predetermined length, defining an internal volume. In particular, the first divider has an inlet opening for the products to be treated, while the second divider has an outlet opening for the treated products.

In addition, the apparatus comprises a conveyor configured to move the products to be treated inside the box-shaped body according to a direction parallel to the longitudinal direction and according to a direction of movement directed from the inlet opening towards the outlet opening. Blowing members are operatively associated with the box-shaped body and configured to generate an air flow within the box-shaped body.

In greater detail, the apparatus comprises temperature adjustment means configured to adjust the temperature of the air flow and preferably arranged inside the box-shaped body along the air flow itself, and at least one dehumidifier operatively associated with the box-shaped body and configured to dehumidify the air flow.

In other words, the apparatus comprises a box-shaped body within which food products are moved by a conveyor in order to receive an appropriate thermal treatment.

To this end, the apparatus comprises blowing means able to convey an air flow through the food products which serves a dual function, that is, to lower the temperature and reduce the humidity contained in the food products which formed with the cooking step. Advantageously, at least a part of the air flow is conveyed through a dehumidifier which reduces the humidity thereof and increases the temperature thereof. In this way, the resulting air flow is sufficiently dry to absorb the greatest quantity of moisture from the food products.

In addition, the temperature adjustment means is configured to reduce the temperature of the air flow so that the latter cools the food products.

Preferably, the blowing members and/or the box-shaped body are configured to direct the air flow along an operating path parallel to the longitudinal direction. The operating path has a first direction opposite the direction of movement of the food products.

Advantageously, conveying the air flow in the direction opposite the direction of movement of the food products increases the efficiency of the treatment, ensuring that the humidity and temperature level of the food products at the outlet of the box-shaped body are within the required limits. According to one aspect of the invention, the box-shaped body comprises at least one dividing element able to subdivide the internal volume between an upper channelling volume and a lower channelling volume along which the products to be treated are transported. More precisely, the dividing element extends along the longitudinal direction for a length less than that of the box-shaped body.

Preferably, the operating path is arranged in the lower channelling volume. The blowing members are configured to direct the air flow inside the upper channelling volume along an auxiliary path parallel to the longitudinal direction and having a second direction in the same direction as the direction of movement. In addition, the second divider and the dividing element are shaped so as to convey the air flow coming from the auxiliary path and direct it in the lower channelling volume along the operating path. Advantageously, the subdivision of the internal volume of the box-shaped body into two distinct volumes allows defining an auxiliary path along which the air flow is generated and an operating volume along which the food products are moved. Specifically, the air flow in the upper channelling volume and the food products in the lower channelling volume have the same direction of advancement along the longitudinal direction. Together with this subdivision, the shape of the dividers allows conveying the air flow circulating between the upper and lower channelling volume.

According to another aspect of the invention, the apparatus comprises an aspiration duct placed in fluid connection with the internal volume and with the dehumidifier to aspirate at least part of the air flow and direct it to the same dehumidifier.

Preferably, the aspiration duct extends between an inlet mouth placed in fluid connection with the upper channelling volume and the dehumidifier.

In this way, the dehumidifier is advantageously arranged outside the box shaped body for better accessibility in case of ordinary checks (i.e. maintenance) or replacement in the case of breakage.

According to a further aspect of the invention, the apparatus comprises a blowing duct interposed between the dehumidifier and the box-shaped body for conveying a dehumidified air flow into the internal volume.

Preferably, the blowing duct extends between the dehumidifier and an outlet mouth placed in fluid connection with the lower channelling volume.

In this way, the dehumidified part of the air flow is again introduced inside the box-shaped body, more precisely in the lower channelling volume, within the total air flow to be conveyed in the direction opposite that of the movement of the food products for their drying and cooling.

Even more preferably, the apparatus comprises a plurality of outlet mouths placed in fluid connection with the lower channelling volume. More precisely, the outlet mouths are arranged equally spaced apart along the longitudinal direction.

Advantageously, in this way the lower channelling volume has a uniform level of humidity, lower than the level contained in the food products, in such a way that the thermal treatment and the absorption of the humidity of the food products by the air flow is optimized.

According to one aspect of the invention, the temperature adjustment means comprises at least one heat exchanger arranged inside the box shaped body along the air flow in order to raise or, preferably, to lower the temperature of the air flow itself.

Advantageously, the route along which the air flow flows has at least one heat exchanger configured to collect and remove the moisture contained in the air itself. Even more advantageously, the heat exchanger is configured to condense the moisture and to lower the temperature of the main air flow F to complete the thermal treatment of the food products.

According to another aspect of the invention, the apparatus comprises means for sanitizing the air, which are arranged inside the box-shaped body. In detail, the sanitization means comprises at least one filter and at least one germicidal lamp.

In this way, the air flow is kept sanitized in that the filter is able to remove the particulate that can seep inside the box-shaped body from the outside and the germicidal lamps are able to reduce the bacterial flora transported. According to a further aspect of the invention, the apparatus comprises cleaning means configured to clean the conveyor and drying means configured to dry the conveyor. Specifically, the cleaning means and the drying means are arranged on the outside of the box-shaped body.

Advantageously, the cleaning means and the drying means are able to carry out a cleaning and sanitizing of the conveyor between the transport of two successive loads of food products.

Preferably, a process for the thermal treatment of food products comprises the steps of:

arranging an apparatus for the thermal treatment of food products, comprising a box-shaped body which extends along a longitudinal direction for a predetermined length, between a first divider and a second divider; moving the food products inside the box-shaped body parallel to the longitudinal direction and according to a direction of movement directed from the first divider towards the second divider;

- generating an air flow within the box-shaped body;

dehumidifying the air flow generated;

adjusting the temperature of the air flow.

Brief description of the drawings

Further characteristics and advantages of the present invention will become more apparent from the indicative, and thus non-limiting, description of a preferred, but not exclusive, embodiment of an apparatus for the thermal treatment of food products, as illustrated in the accompanying drawings, in which:

- figure 1 shows, according to a side view, a section of the apparatus for the thermal treatment of food products;

- figure 2 shows, according to a view from above, the apparatus for the thermal treatment of food products.

With reference to the drawings, they serve solely to illustrate embodiments of the invention with the aim of better clarifying, in combination with the description, the inventive principles at the basis of the invention.

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Detailed description of preferred embodiments of the invention

The present invention relates to an apparatus for the thermal treatment of food products.

With reference to the figures, an apparatus for the thermal treatment of food products has been generically indicated with the number 1 .

The other numerical references refer to technical features of the invention which, barring indications otherwise or evident structural incompatibilities, the person skilled in the art will know how to apply to all the variant embodiments described.

Any modifications or variants which, in the light of the description, are evident to the person skilled in the art, must be considered to fall within the scope of protection established by the present invention, according to considerations of technical equivalence.

Figure 1 shows an apparatus 1 for the thermal treatment of food products. In detail, the apparatus 1 comprises a box-shaped body 2 which extends along a longitudinal direction L for a predetermined length. In greater detail, the length of the extension of the box-shaped body 2 is variable, for example between 50 metres and 80 metres, depending on the type of food product that is to be treated.

The box-shaped body 2 has a first divider 3 and a second divider 4 opposite each other along the longitudinal direction L.

An internal volume V of the apparatus 1 is defined within the box-shaped body. The box-shaped body 2 is configured to isolate the internal volume V thereof from a volume outside the apparatus 1 , to reduce the possible infiltration of contaminants.

The first divider 3 has an inlet opening 30 for the products to be treated, while the second divider 4 has an outlet opening 40 for the treated products. Preferably, the first and the second divider define the respective inlet and outlet openings for the passage of the food products, as they have a curved shape that does not totally cover the cross section of the box-shaped body 2 relative to the longitudinal direction L.

For example, the box-shaped body 2 has the shape of a "tunnel" that extends between the inlet opening 30 for the products to be treated and the outlet opening 40 for the treated products.

Preferably, each insulating panel that composes the box-shaped body 2, or more generally the apparatus 1 , is made of a material suited for use with food. The panels are also equipped with hinges and handles for their easy opening in order to simplify any inspection of the internal volume V.

According to a preferred embodiment of the invention, the apparatus 1 comprises a conveyor 5 which allows moving the food products inside the box-shaped body 2. The conveyor 5, preferably a conveyor belt, is configured to move the food products along a direction parallel to the longitudinal direction L and according to a direction of movement S directed from the inlet opening 30 towards the outlet opening 40. Preferably, the conveyor belt has a double tow so as to reduce the typical slippage of conveyor belts that extend for lengths greater than 20 metres. In detail, a first tow is installed at the inlet opening 30 of the food products, and a second tow is installed at the outlet opening 40.

Preferably, the conveyor belt 5 is configured to maintain the products to be treated stably in position during the conveyance so as to prevent the movement of the same that could adversely affect the subsequent work of the apparatus 1 .

Advantageously, the apparatus 1 comprises blowing members 6 operatively associated with the box-shaped body 2 and configured to generate a main air flow F inside the box-shaped body 2 itself in order to accelerate the cooling of the food products. Preferably, the blowing members 6 comprise an impeller, a propeller or a centrifugal fan, for example of the "plug-fan” type coupled in direct contact with an electric motor 12.

The blowing members 6 are configured to generate the main air flow F along an operating path parallel to the longitudinal direction L and having a first direction V1 opposite the direction of movement S of the food products.

In other words, the blowing members 6 and/or temperature adjustment means 7 are configured to manage the intensity and/or the temperature of the main air flow F in order to remove the moisture formed in the same products during the cooking step, but without excessively cooling them, thus avoiding the freezing of the moisture inside the food products which has not yet absorbed. In particular, the main air flow F comprises, at least in part, the direction opposite the direction of movement S of the food products and incident on the latter in order to cool and dehumidify them.

Preferably, as shown in figure 1 , the box-shaped body 2 comprises at least one dividing element 9 which extends along the longitudinal direction L and is configured to subdivide the internal volume V of the box-shaped body 2 in an upper channelling volume W and a lower channelling volume M. Preferably the dividing element 9 extends along the longitudinal direction L for a length less than that of the box-shaped body 2 itself.

In this way, the dividing element 9 generates a looped path that extends between the upper channelling volume W, and the lower channelling volume M.

Advantageously, the blowing members 6 are configured to generate the main air flow F from the upper channelling volume W and the food products to be treated are transported along the lower channelling volume M.

More specifically, the blowing members 6 are arranged in the box-shaped body 2 in the proximity of the inlet opening 30 and are configured for channelling the main air flow F inside the upper channelling volume W along an auxiliary path parallel to the longitudinal direction L and having a second direction V2 in the same direction as the direction of movement S of the food products.

According to an advantageous aspect of the invention, the curved shape of the second divider 4 is able to convey the main air flow F from the upper channelling volume W to the lower channelling volume M, along the operating path travelled crossed by the food products.

Similarly, the curved shape of the first divider 3 is able to again convey in the upper channelling volume W the main air flow F that has crossed the operating path, to be recirculated by the blowing members 6.

Advantageously, between the first divider 3 and the blowing members 6, the apparatus 1 comprises air sanitization means, which is arranged along the main air flow F and comprises at least one filter 10 and at least one germicidal lamp 1 1 . The filter 10, for example a gravimetric filter, is configured to intercept and eliminate dust and coarse particulate which is able to infiltrate inside the box-shaped body 2. The germicidal lamp 1 1 (UV- C) allows reaching a sanitization level of 99%, reducing the proliferation of viruses, bacteria, mould, spores or other highly polluted agents harmful to health. Managing to uniformly treat the main air flow F which crosses the germicidal lamp 1 1 , the apparatus 1 is configured to eliminate the bacterial load and the distribution of dangerous and bothersome pathogens. The apparatus 1 is also capable of inhibiting the creation of biofilm on the inner surfaces of its box-shaped body 2, which would be the result of the presence of specific microorganisms and conditions favourable to their proliferation (such as temperature changes, high levels of air humidity and darkness). According to an advantageous embodiment of the invention, the apparatus 1 comprises temperature adjustment means 7 and at least one dehumidifier 8.

Preferably, the temperature adjustment means 7 comprises at least one heat exchanger arranged inside the box-shaped body 2 (figure 1 ) and along the main air flow F to adjust the temperature of the main air flow F itself, raising it or lowering it as a function of the type of food product that must be treated.

When the main air flow F collides with a heat exchanger, if the temperature of the latter is less than that of the air, the humidity present in the flow tends to condense and can thus easily be collected and removed outwardly from the apparatus 1 by means of special tanks and drain ducts.

According to an aspect of the invention, the temperature adjustment means 7 is arranged in the lower channelling volume M.

Preferably, each heat exchanger is arranged along the operating path of the main air flow F, as it is along this path that a temperature control of relatively moist air is preferably required because it is in contact with the products moved along the direction of movement S opposite the first direction V1 of the main air flow F in the lower channelling volume M.

According to a possible aspect of the invention, the dehumidifier 8 is a dehumidifier with an absorption rotor used for the dehumidification of the main air flow F. Preferably, the dehumidifier 8 is operatively associated with the box-shaped body 2 outside the latter, as better visible in figure 2.

According to another aspect of the invention, the humidifier 8 is configured to generate a dehumidified air flow H at a temperature greater than 50 °C, preferably greater than 70 °C, even more preferably at about 100 °C.

To further accelerate the thermal treatment of the food products, at least part of the main air flow F is conveyed through the dehumidifier 8 so that the latter reduces the humidity level before again channelling the flow in the internal volume V for the thermal treatment of the food products. In other words, the dehumidifier 8 is configured to generate a dehumidified air flow H, and therefore dry, so that the relative pressure gradient that is established between the dry air (high pressure, low water vapour content) and the food products (low pressure, high water vapour content) accelerates the thermal treatment of the food products because the system consisting of dry air and moist products tends to a value of intermediate balance. In practice, the pressure difference creates a vacuum effect on the outside of the food products, which will force the passage of the humidity contained in the most central area of the food products towards the outside, avoiding the freezing of the same during the treatment and the formation of free water within the preserved product.

To advantageously convey at least part of the main air flow F towards the dehumidifier 8, the apparatus 1 comprises an aspiration duct 80 placed in fluid connection with the internal volume V and the dehumidifier 8. More precisely, the aspiration duct 80 extends between an inlet mouth 81 placed in fluid connection with the upper channelling volume W, if present, and the dehumidifier 8. Preferably, the aspiration duct 80 is connected to an aspirator to force the aspiration of at least a part of the main air flow F flowing through the upper channelling volume W towards the dehumidifier 8.

The apparatus 1 comprises a blowing duct 85 interposed between the dehumidifier 8 and the box-shaped body 2 for conveying the dehumidified air flow H in the internal volume V. In detail, the blowing duct 85 extends between the dehumidifier 8 and at least one outlet mouth 87 placed in fluid connection with the lower channelling volume M, if present.

As for example illustrated in figure 1 and in figure 2, the blowing duct 85 can have one or more outlet mouths 87, for example three distinct mouths. Preferably all of the outlet mouths 87 are placed directly in fluid connection with the lower channelling volume M, if present. Even more preferably, these outlet mouths 87 are arranged at the same distance from each other along the longitudinal direction L so that the blowing of the dehumidified air flow H occurs in a homogeneous manner inside the lower channelling volume M.

According to an aspect of the invention shown in figure 1 and in figure 2, the blowing duct 85 and each outlet mouth 87 are separated by the upper channelling volume W so that the dehumidified air flow H mixes with the main air flow F at the lower channelling volume M.

In other words, a primary air flow and a secondary air flow are channelled inside the apparatus 1 . The primary air flow is the main air flow F conveyed within the box-shaped body 2 to describe a cyclic path composed of the operating path and the auxiliary path. The secondary air flow is the dehumidified air flow FI conveyed through the blowing duct 85, downstream of the dehumidifier 8, to be introduced directly inside the lower channelling volume M of the box-shaped body 2.

Consequently, at least at the lower channelling volume M along the operating path, the primary air flow also comprises the secondary air flow, i.e. the main air flow F comprises the dehumidified air flow FI because it is mixed together.

More precisely, therefore, the apparatus 1 is configured to treat with the dehumidifier 8 only one portion of the main air flow F, since to thermally treat the food products it is advantageous that the main air flow F, generally containing part of the moisture of the products, is mixed with the correct proportions with the dehumidified air flow FI, which is drier than the primary flow. In this way, an improvement of the removal capacity of the excess moisture from the food products is guaranteed, which, at the same time, do not maintain a correct value of internal moisture to preserve the taste thereof, making them not overly dry due to the treatment with only dehumidified air (as implemented by the prior art for example).

Advantageously, the apparatus 1 comprises an electric control panel used for the setting and control of the various settings of the components to which it is connected, among which there are the conveyor 5, for the speed control, the blowing members 6, for the management of the main air flow F, the dehumidifier 8, to establish the reference humidity level at which the main air flow F is to be maintained, and the temperature adjustment means 7, to set the temperature level to which the main air flow F must be brought, added with the possible dehumidified air flow H. All these parameters are adjustable as a function of the food product that is to be thermally treated and the times in which it is to be treated. The length for which the box shaped body 2 extends can also be selected in advance, in the design phase, as a function of the food product that is to be thermally treated and the times in which it is to be treated.

According to an aspect of the invention not shown in the attached figures, the apparatus 1 comprises cleaning means and drying means configured, respectively, to clean and to dry the conveyor 5.

The cleaning means and drying means are preferably arranged on the outside of the box-shaped body 2 for washing and drying a moving portion of the conveyor belt from the outlet opening 40 towards the inlet opening 30, before a new load of food products is housed therein.

With regard to an operating example of the apparatus 1 , it derives directly from what is described above and which is referred to below.

Initially, the food products are arranged on the conveyor 5 associated with the box-shaped body 2 of the apparatus 1 , at the inlet opening 30.

The food products are then made to advance inside the box-shaped body 2 along the longitudinal direction L towards the outlet opening 40. Simultaneously to the activation of the conveyor 5 and, therefore, the advancement of the food products, the centrifugal fan configured to generate the main air flow F in the upper channelling volume W along the auxiliary path is also activated. Given the presence of the dividing element 9 and given the shape of the dividers, the main air flow F at the end of the auxiliary path is conveyed into the lower channelling volume M, along the operating path where it meets the food products in the direction opposite their direction of movement S to then be conveyed again to the upper channelling volume W, where the centrifugal fan maintains the air circulation constant in such a way that the path just described repeats.

Simultaneously to the activation of the centrifugal fan, the activation of the heat exchangers is provided.

The heat exchangers arranged along the operating path preferably lower the temperature of the main air flow F and cause the collected moisture to condense.

In addition, an aspirator aspirates part of the air flow from the upper channelling volume W to transfer it to the dehumidifier 8 that dehumidifies it and conveys it towards the lower channelling volume M, where it is able to absorb the excess moisture of the food products which are cooled at the same time by the same main air flow F.

Finally, the products that reach the outlet opening 40 can be withdrawn and carried to other machinery for any other processing or for their conservation. With regard to an operating example of the apparatus 1 for thermal treatment, it derives directly from what is described above and which is referred to below with the illustration of a relative process.

A process for the thermal treatment of food products, comprising the steps of:

arranging an apparatus 1 for the thermal treatment of food products, comprising a box-shaped body 2 which extends along a longitudinal direction L for a predetermined length, between a first divider 3 and a second divider 4. The first divider 3 has an inlet opening 30 for the products to be treated, while the second divider 4 has an outlet opening 40 for the treated products;

arranging a dividing element 9 extending along the longitudinal direction L for a length less than that of the box-shaped body 2 and adapted to subdivide an internal volume V of the box-shaped body 2 between an upper channelling volume W and a lower channelling volume M along which the products to be treated are conveyed;

moving the food products inside the box-shaped body 2 according to a direction parallel to the longitudinal direction L and according to a direction of movement S directed from the inlet opening 30 to the outlet opening 40;

generating an air flow F within the box-shaped body 2;

withdrawing at least a part of said main air flow F;

dehumidifying said main air flow F withdrawn to generate a dehumidified air flow H;

introducing said dehumidified air flow H in the lower channelling volume M through a blowing duct 85 separated from the upper channelling volume W so that the dehumidified air flow H mixes with the main air flow F at the lower channelling volume M;

adjusting the temperature of the main air flow F in which the dehumidified air flow H was introduced.

According to an aspect of the invention, the step of generating a main air flow F provides cyclically conveying the same main air flow F inside the box shaped body 2 so that it is channelled into the lower channelling volume M, along an operating path parallel to the longitudinal direction L having a first direction V1 opposite the direction of movement S, and also in the upper channelling volume W, along an auxiliary path parallel to the longitudinal direction L having a second direction V2 opposite the first direction V1.

According to an aspect of the invention, the step of withdrawing at least a part of the main air flow F acts on the latter when it is channelled along the auxiliary path.

According to an aspect of the invention, the step of introducing the dehumidified air flow H in the main air flow F acts on the latter, or more precisely on a portion thereof, when it is in the upper channelling volume W, channelled along the operating path, so that the dehumidified air and the humid air mix at the products moved along the direction of movement S. According to an aspect of the invention, the step of dehumidifying the main air flow F provides for generating a dehumidified air flow FI at a temperature greater than that of the main air flow F flowing in the upper channelling volume W.

According to another aspect of the invention, the step of adjusting the temperature of the main air flow F in which the dehumidified air flow FI was introduced takes place at the lower channelling volume M and provides for cooling the air flow moving in the lower channelling volume M.