The present invention relates to a method for a cooking apparatus and cooking apparatuses for cooking or baking foods, of the type having a cooking chamber, like cooking ovens, both for domestic and for professional use. Within this general scope, the present invention relates to improvements in respect of the treatment of vapors produced in the cooking chamber while cooking food. In the rest of the description, with "cooking" it will be intended any kind of preparation of foods by heat, including baking.

Cooking apparatuses comprise a cooking chamber in which food is cooked. During the cooking process, vapors forms in the cooking chamber of the cooking apparatus. Vapors are predominantly in the form of steam and consist of water vapor for the most part; in addition, they also contain oils and fats, which are present in the form of aerosols or else in liquid form. Other components may also be contained therein.

Vapors are created during the cooking process through the vaporization of water that is naturally contained in the foods being cooked; in addition, however, vapor that is deliberately fed into the cooking chamber of the apparatus (either by way of an external steam generator or else by direct vaporization of water inside of the hot cooking chamber) for some types of cooking also contributes to the creation of vapors. This water vapor is intentional and is important for certain aspects of the cooking process.

When fat-containing foods or fat-containing cooking products are cooked at high temperatures, the aforementioned oil and fat aerosols are additionally created.

Vapors in excess must be exhausted to the outside, otherwise an undesired vapor pressure would build up within the cooking chamber. Some conventional cooking apparatuses have an exhaust air opening from which steam or vapors can escape into the room air, but this can lead to a strong accumulation of moisture and heat in the room air in the surroundings of the cooking apparatus and in the entire kitchen premises; moreover, the room is also dirtied by the oil and fat aerosols contained in the escaped vapors. All this is totally unsatisfying.

US 2011/072983 discloses a cooking apparatus having a cooking chamber, wherein the vapors created in the cooking chamber are removed with a vapor outlet channel. A vapor condensation device brings the vapors into contact with a cooling liquid. The vapor condensation device has a container, in which a liquid bath is located. The vapor outlet channel carries the vapors out of the cooking chamber into the container of the vapor condensation device. There, the vapors are brought into contact with the liquid from the liquid bath and thereby partially condensed. Furthermore, a device drain is provided. The container of the vapor condensation device has a vapor guide element, that guides the vapors through one or more channels in the container; the vapor guide element is configured such that one wall of the wall surfaces of the channel or channels is formed by the surface of the liquid bath in the container.

EP 691513 discloses an oven having a cooking interior enclosed by a door and casing. There is a heater and floor drain removing condensate. Above the oven, an extraction hood removes water vapor, via a fan. Preferably, a suction duct connects the extraction hood to drain. A hood intake is immediately above the door opening and leads to a condenser integral with the hood; this has vertical baffle surfaces defining a steam channel. The base surfaces slant toward the extraction duct connection.

DE 88 05 455 U1 discloses a device for condensing a vapor mist from bakeries and the like with one of several chambers of a condensation housing, where the vapor, inter alia, is directed on a condensation material sprayed of water. The chambers are arranged parallel to each other and at their lower and upper ends openings for the vapor passage are provided.

EP 0 671 591 A1 discloses a device for removing cooking fumes from a baking oven. The extraction system has an electric fan for discharging steam and hot air through a vent line provided between the kitchen wall and the rear of the built-in kitchen cabinet above the oven, communicating with an exit opening at the rear of the oven space. A cold air blower is provided in space between a heating chamber and the steam extraction fan. The vent line may also communicate with side and upper gaps between the oven housing and the adjacent kitchen cabinets, with a resilient section at the oven end of the vent line, for sealing against the oven housing and/or the cabinet above it.

DE 197 20 736 A1 discloses an appliance for cooking food using hot steam in sealable cooking compartment. The cooking appliance has a sealable cooking compartment, in which units are provided for leading in or producing steam. An outlet is provided for leading off any excess steam. The outlet communicates with a coolable condensation unit, arranged outside the cooking compartment, which effects the condensation of the excess steam. The condensation unit is coolable pref. actively across a fan. The condensation unit includes a heat exchanger. The condensation unit includes a heat conducting pipe. The condensation unit can have cooked condensation plates, pref. of aluminium, at which the excess steam is condensed.

EP 0 732 549 A2 discloses an oven for the heat treatment of food and method of baking. The oven has a chamber with an air intake. This is connected to an intake channel, which opens near the top end of the oven door. The oven also has an external exhaust ventilator, connected to an exhaust air aperture. The intake side of the ventilator is connected to the intake channel, while its pressure side is connected to the exhaust air aperture. The oven door has at least one lower intake aperture, and an upper discharge aperture near the top of the door and the opening of the intake channel. The two apertures are connected via a channel.

JP 2010 139177 A discloses a solution to the problem of providing a heating cooker capable of removing smoke without using an expensive catalyst. A ventilation port formed on a back face of a roaster chamber is communicated with a smoke exhaust passage (same as a smoke exhaust duct), and a high temperature smoke removing part for heating passing gas is provided in a position near the ventilation port in the smoke exhaust passage so as to enable ventilation. The high temperature smoke removing part is heated to high temperature by electrical heating and electromagnetic induction heating.

WO 2012/029691 A1 discloses a heating cooker comprising: a casing; a heating chamber disposed in the casing and having a front opening; an exhaust tube for guiding gas from the inside of the heating chamber to the front side of the casing; a cooling fan disposed in the casing; and an exhaust duct having an exhaust inlet to which the other end of the exhaust tube is connected. The height of a cooling air inlet for introducing cooling air into the exhaust duct through the lower side of the exhaust duct is lower than the height of an outlet of the exhaust duct, and the height of the cooling air inlet of the exhaust duct is lower than the height of the exhaust inlet of the exhaust duct. Even if air to be mixed with exhaust gas cannot be supplied due to malfunction of the fan, the exhaust gas from the heating chamber does not flow into a main body of the heating cooker.

DE29602748 discloses a device for treating vapours produced in an oven chamber during a food cooking process

The Applicant has tackled the problem of devising a solution for providing an oven with an improved treatment of vapors produced in the cooking chamber while cooking or baking food.

According to an aspect of the present invention, there is provided an oven comprising an oven chamber for the cooking of foods, heating means for heating the oven chamber, and a vapor exhaust system for treating vapors produced in the oven chamber during a food cooking process.

The vapor exhaust system comprises:

• a first region in fluid communication with the oven chamber so as to receive vapors exiting the oven chamber and wherein the vapors are de-moisturized and cooled down; and
• a second region downstream the first region and wherein the de-moisturized and cooled down vapors exiting the first region are mixed to hot dry air before being exhausted to the outside ambient.

Therefore, the oven has, associated with the first region, means for demoisturize and cool down vapors received from the oven chamber, and, associated with the second region, means for mixing hot dry air to the vapors exiting the first region.

Preferably, said first region extends vertically.

According to the invention, in the first region a tortuous path for the vapors is formed.

Said tortuous path may be a duct comprising a plurality of baffles.

In an embodiment, at least one of said baffles is hollow and is run through a heat-exchange fluid.

Advantageously, a coolant liquid feeding device may be associated with said first region, arranged for feeding a coolant liquid into the first region for cooling down the vapors.

Said coolant liquid feeding device may comprise at least one liquid feeding nozzle adapted to spray coolant liquid into said first region in a nebulized form.

Said coolant liquid feeding device may for example be arranged to cause the coolant liquid to enter into the first region proximate to a top side thereof.

Said coolant liquid feeding device is preferably connected to an activator adapted to selectively activate said coolant liquid feeding device for selectively feeding the coolant liquid.

Preferably, at least a temperature sensor is associated with the first region, arranged for sensing the temperature of the vapors entering into the vapors exhaust system.

Said coolant liquid feeding device may be selectively activated based on a sensed temperature of the vapors sensed by said temperature sensor.

The oven may comprise at least an air propeller associated with said vapor exhaust system and configured for promoting the exit of vapors from the oven chamber and their flow through the vapor exhaust system.

Said air propeller may comprise an axial or radial fan arranged at the exit of the second region.

Said air propeller may be selectively activatable.

Advantageously, said hot dry air comprises air exploited to cool down at least one among a door of the oven and/or air exploited to cool down internal oven parts subjected to heat up during the oven operation.

The following detailed description of exemplary and non-limitative embodiments of the present invention will help to render the above as well as other features and advantages of the present invention clearer. For its better intelligibility, the following description should be read while referring to the attached drawings, wherein:

• FIG. 1 schematically shows an oven according to an embodiment of the present invention, in cross-section according to a vertical plane orthogonal to a front of the oven;
• FIG. 2 schematically shows the oven of FIG. 1 in cross section according to a plane parallel to the front of the oven, indicated in FIG. 1 as II-II;
• FIG. 3 schematically shows the oven of FIG. 1 and FIG. 2 in cross section according to a horizontal plane, indicated in FIG. 2 as III-III;
• Fig. 4 is a schematization of a vapor exhaust tower of the oven of FIG. 1 to FIG. 3, with indicated different vapor control regions;
• FIG. 5 is a schematization similar to FIG. 4, with notations used in a mathematical analysis of the different vapor control regions;
• FIG. 6 is a simplified Carrier diagram or psychrometric chart (specific humidity in ordinate versus temperature in abscissa), of the humid air for a first control region of the vapor exhaust tower;
• FIG. 7 is a complete Carrier diagram of the humid air for a first control region of the vapor exhaust tower;
• FIG. 8 is a complete Carrier diagram of the humid air for a second control region of the vapor exhaust tower;
• FIG. 9 is a schematic flowchart of an exemplary way of operation of the oven according to an embodiment of the present invention, and
• FIG. 10 shows, in a schematical view similar to that of FIG. 5, a vapor exhaust tower according to another embodiment of the present invention.

Referring to FIG. 1, FIG. 2 and FIG. 3, an oven according to an embodiment of the present invention is schematically depicted, in three cross-sectional views (as explained in the Brief description of the drawings).

The oven, denoted as a whole 100, comprises an oven chamber 105 (cooking chamber) wherein the foods to be cooked/backed are to be introduced for being cooked.

The oven chamber 105 is a delimited region of space within an oven cabinet 110 having a front opening 115 for inserting/removing the foods, which is selectively closable by an oven door 120, hinged to the oven cabinet 110 so as to be movable by an oven user between a closed position (the one depicted in FIG. 1) adapted to close the front opening 115, and an open position (not depicted in the drawings) in which the oven chamber 105 is accessible through the front opening 115.

Inside the oven chamber 105, heating elements 125, for example one or more resistive heaters, are provided, energizable for heating up the oven chamber environment.

Preferably, an air propeller 130 is also provided inside the oven chamber 105, operable (possibly in a selective way, depending on a food cooking program selected by the oven user) to cause air circulation within the oven chamber 105 so as to better distribute the air heated up by the heating elements 125 and achieve a more uniform temperature inside the oven chamber 105.

It is pointed out that although in FIG. 1 the heating elements 125 are depicted as arranged at the periphery of the air propeller 130, this is merely an example; the heating elements might be arranged in different locations, and/or additional heating elements might be arranged in different locations of the oven chamber 105, e.g. at the top and/or at the bottom thereof.

The oven door 120 is designed so to have an air gap 135 formed therein, for the passage of cooling air 140 having the function of cooling the external panel 145 (usually of glass or other transparent material) of the oven door 120, in order to keep such external panel at a temperature sufficiently low not to be harmful for the oven user. The oven door cooling air 140 is for example taken in from the outside ambient, e.g. through an opening formed at the bottom of the door 120.

In a space formed between the oven chamber 105 and the walls of the oven cabinet 110, thermally-insulating material 150 is preferably provided, in order to avoid heat dissipation from inside the oven chamber 105 to the outside ambient, and at the same time reducing the temperature of the cabinet walls when the oven 100 is operating.

Albeit not shown, it is intended that the oven 100 may comprise several other components, like for example a steam and/or microwaves generator(s) to be supplied to the oven chamber 105 for performing some particular kinds of cooking processes.

According to the present invention, the oven 100 is equipped with a system for exhausting vapors that are produced within the oven chamber 105 when foods are cooked. Advantageously, the vapor exhaust system is integrated, embedded in the structure of the oven 100.

In the exemplary embodiment of the present invention here presented, the vapor exhaust system comprises a vapor exhaust tower 155 which is accommodated at the rear of the oven 100, e.g. approximately at the center or more or less proximate to a corner of the oven cabinet 110, like the rear-left corner (looking the oven 100 frontally), as shown in the drawings (it is intended that the position of the vapor exhaust tower 155 is not at all limitative for the present invention).

The vapor exhaust tower 155 according to an embodiment of the present invention will be hereafter described with the help of the principle schematic of FIG. 4.

The concept at the basis of the vapor exhaust tower 155 according to the present invention is the (selective) superposition of three physical phenomena: a dehumidification, de-hydration, moisture condensation of the vapors coming from the oven chamber 105 (phenomenon A); a cooling of the vapors (phenomenon B), and an adiabatic intermixing of the vapors with relatively hot and dry air (phenomenon C).

In an embodiment of the present invention, phenomena A and B may take place concurrently, as depicted in the schema of FIG. 4, in a bottom section 405 of the exhaust tower 155; phenomenon C takes place in a top section 410 of the exhaust tower 155.

Referring back to FIG. 1 and FIG. 2, the exhaust tower 155 is, at a bottom thereof (i.e., at a bottom of the bottom section 405), fluidly connected to a vapor discharge duct 160 that, having an inlet 165 preferably at the bottom of the oven chamber 105 (e.g., approximately in the central position), runs, preferably declining, towards an outlet 170 opening approximately at the bottom of the exhaust tower bottom section 405.

The bottom of the exhaust tower bottom section 405 is also fluidly connected to a liquid drainage 175 (only part of which is shown), which, when the oven is installed in a kitchen, is connected to a kitchen water drainage spigot.

In the exhaust tower bottom section 405, a tortuous, sinuous, serpentine, labyrinthic path is formed, for example, as in the example depicted in the drawings, by means of properly offset baffles 177.

In a vertical position along the exhaust tower bottom section 405, vertical position that in the shown embodiment is approximately at the top of the exhaust tower bottom section 405, an inlet 415 for a cooling liquid is advantageously present, which for example may comprise a nozzle for spraying cooling water that is selectively fed, for example under control of a valve 420, e.g. an electrovalve, controlled by an oven control unit (shown only schematically in FIG. 4 and denoted 423). The nozzle preferably is adapted to spray water in a nebulized form, i.e. as very small droplets. The cooling water is for example fed via a piping that, when the oven is installed, is coupled to a water outlet spigot of the kitchen.

Preferably, a temperature sensor 425 may be provided in a vertical position along the exhaust tower bottom section 405, for example approximately at the bottom of the exhaust tower bottom section 405, proximate to the outlet of the vapor discharge duct 160. When present, the temperature sensor 425 is in signal connection with the oven control unit 423 to communicate thereto the readings about the temperature of the vapors exiting the oven chamber 105. The oven control unit 423 may for example be programmed so as to activate the electrovalve 420 when the temperature of the vapors exiting the oven chamber 105 (and entering the vapor exhaust tower 155) reaches a pre-set temperature, which may also depend on the specific cooking programme selected by the oven user.

At a top thereof, the exhaust tower bottom section 405 has an opening 430 leading into the exhaust tower top section 410, which is for example more or less vertically aligned to the underlying bottom section 405. The exhaust tower top section 410 has one or more inlets for relatively hot and dry air, which is introduced so as to be intermixed to the de-moisturized vapor that, after exiting the oven chamber 105, has passed through the exhaust tower bottom section 405. The exhaust tower top section 410 may include a first hot air inlet 433, in the shown example located more or less midway the exhaust tower top section 410, for admitting hot air that has been taken in from the outside ambient for cooling oven parts like the motor for the air propeller 130, among which there may be the exhaust tower bottom section 405, and a second hot air inlet 435, in the shown example located more or less at the top of the exhaust tower top section 410, for admitting the oven door cooling air 140, that, after passing in the gap 135 formed in the oven door 120, passes in a gap between the oven chamber 105 and a top panel of the oven cabinet 110.

A fan 180 is advantageously provided at the top of the exhaust tower top section 410. The fan 180, that preferably is selectively activatable by the oven control unit 423, creates a depression inside the exhaust tower 155 and sucks the vapor and the cooling fluxes inside it. Downstream the fan 180, i.e. on top of it, the exhaust tower 155 opens into the external ambient or into a discharge duct.

For the sake of explanation of its principle of operation, the system for exhausting vapor according to an embodiment of the present invention can advantageously be regarded as made up by two so-called "control regions". A first control region is the exhaust tower bottom section 405, where the phenomena A and B take place. A second control region is the exhaust tower top section 410, where the phenomenon C takes place.

In the first control region 405, the labyrinthic path formed by the baffles 177 allows compactizing the vapor exhaust tower 155, thereby reducing its space occupation.

When the electrovalve 420 is open and the nozzle 415 sprays cooling water, thanks to the presence of the baffles 177 a sort of waterfall-type filter is formed, that at each fall condenses the vapors exiting the oven chamber 105 and filters them by retaining the particles of fat transported by the vapors.

The baffles 177 allows the cooling water, sprayed by the nozzle 415, to have more time and surface area available for enhancing heat exchange between the sprayed cooling water and the vapors coming from the oven chamber 105. In addition, the presence of the baffles 177 enables the sprayed cooling water to release at least part of the heat absorbed by the vapors to the baffles 177 and the walls of the vapor exhaust tower 155 (this heat can then be dispersed outside the vapor exhaust tower 155, and may advantageously contribute to heating up the air that is then introduced into the exhaust tower top section 410 through the first air inlet 433). Concurrently, the injected cooling water cools down the baffles 177, on which the moisture contained in the vapors can condensate.

The injection of the cooling water by the nozzle 415 in the form of nebulized droplets, creates a sort of fog inside the first control region 405, that contributes to the increase of the thermal exchange area and at the same time reduces the power and resources (water) consumption and the generated noise.

In the second control region 410, the heat released by the vapors passing through the first control region (exhaust tower bottom section) 405 as well as by the operation of the oven (e.g., the motor of the air propeller 130) is caused to be absorbed by the cooling air (that enters into the vapor exhaust tower 155 through the first hot air inlet 433), thereby increasing the temperature thereof. This allows to reduce the relative humidity of the cooling air (at constant specific humidity), thereby increasing the capacity of the cooling air of absorbing the residual humidity of the vapors exiting the first control region 405, when they are mixed with the cooling air: in fact, by increasing the temperature of the cooling air, the specific humidity of the flow of intermixed vapors and cooling air remains substantially the same, while the relative humidity decreases; the capability of absorbing the humidity contained in the flow of vapors is thus increased.

FIG. 5 schematizes again the vapor exhaust system according to an embodiment of the present invention, and should be referred to as an aid for the following analytical analysis of the energy and mass balance. Hereafter, for the purpose of notation, it is assumed that the normal to the control regions is directed as exiting the surface delimiting the control regions. The mechanical work is regarded as positive if exiting the control regions (i.e., when directed as the normal to the control regions) whereas the heat is regarded as positive if entering into the control regions (i.e., when opposite to the normal). The energy and mass flows are regarded as positive if directed as the normal to the control regions.

The vapor exhaust system according to an embodiment of the present invention can be regarded as comprised of three "control volumes" or "control regions": the first and second control regions 405 and 410 introduced in the foregoing, and a third control region made up by the union of the first and second control regions 405 and 410.

For the purpose of notation, hereinafter the terms ṁ denote mass flow rates of dry air; the subscript "steam" denotes the flows containing a certain amount of vapor. In any case, the term ṁ is to be intended as referred to the fraction of dry air present in a flow, whereas the fraction of humid air present in a flow is denoted as ṁ · x, with x denoting the specific humidity. The terms with subscript "engine" or "door" refer to the flux of cooling air of the engine of the air propeller 130 (entering into the vapor exhaust tower 155 through the inlet opening 433) and, respectively, of the flux 140 of the cooling air of the oven door (entering into the vapor exhaust tower 155 through the opening 435).

Let:

• r₀ be the water vaporization heat (water vaporization enthalpy), and
• c_p, c_v constants.

Then: $$x=\frac{m_{\mathit{vapour}}}{m_{\mathit{air}}},\varphi =\frac{m_{\mathit{vapour}}}{m_{\mathit{saturation}}};$$ where x denotes the specific humidity and φ denotes the relative humidity,
and where the mass flows rates ṁ_steam and ṁ_steam2 of dry air entering and exiting the first control region 405 (equal to each other, since as mentioned above the mass flow rates are referred to the fraction of dry air) are defined as ṁ_a: $${\dot{m}}_a={\dot{m}}_{\mathit{steam}}={\dot{m}}_{\mathit{steam}2}$$

The energy and mass balance equations for the first control region 405 are: $$Q_1^{-}={\dot{m}}_a\left(h_{\mathit{steam}2}-h_{\mathit{steam}}\right)+{\dot{m}}_{H2O_{\mathit{out}}}{h}_{H2O_{\mathit{out}}}-{\dot{m}}_{H2O}{h}_{H2O}$$ $${\dot{m}}_{H2O_{\mathit{out}}}={\dot{m}}_{H2O}+{\dot{m}}_a\left(x_{\mathit{steam}}-x_{\mathit{steam}2}\right)$$ where the first equation (Eq. (1)) relates to energy (the suffix "-" for the heat Q₁ means that the heat exits the control region; the symbols h denote the enthalpy), and the second equation (Eq. (2)) relates to the mass of water. The term (x_steam - x_steam2) is due to the condensation of moisture.

In order to solve the first equation Eq. (1) for the energy, let FIG. 6 be considered, showing a simplified Carrier diagram for humid air. The transformation "1 → 2" marked on the diagram can be decomposed into the two transformations "1 → 3" (latent contribution) and "3 → 2" (sensible contribution).

Considering that: $$\dot{m}\left(h_2-h_1\right)=\dot{m}\left[{\left(\frac{\partial h}{\partial t}\right)}_x\cdot \mathrm{\Delta }t+{\left(\frac{\partial h}{\partial x}\right)}_t\cdot \mathrm{\Delta }x\right]$$ $$h=h_a+x\cdot h_v$$ where h_a denotes the enthalpy of a dry air flow and h_v denotes the enthalpy of a flow of humid air, being: $$\begin{array}{c}{h}_a=c_{\mathit{pa}}\cdot t\\ h_v=r_0+c_{\mathit{pv}}\cdot t\end{array}$$ it follows that Eq. (4) becomes: $$h=c_{\mathit{pa}}\cdot t+x\cdot \left(r_0+c_{\mathit{pv}}\cdot t\right)$$ and then, by derivation of Eq. (5): $${\left(\frac{\partial h}{\partial t}\right)}_x=c_{\mathit{pa}}+x\cdot c_{\mathit{pv}}$$ $${\left(\frac{\partial h}{\partial x}\right)}_t=r_0+c_{\mathit{pv}}\cdot t$$

The energy balance equation (Eq. (1)) can thus be developed as: $$Q_1^{-}={\dot{m}}_a\left(c_{\mathit{pa}}+x_{\mathit{steam}2}\cdot c_{\mathit{pv}}\right)\left(t_{\mathit{steam}2}-t_{\mathit{steam}}\right)+{\dot{m}}_a\left(r_0+c_{\mathit{pv}}\cdot t_{\mathit{steam}}\right)\left(x_{\mathit{steam}2}-x_{\mathit{steam}}\right)+{\dot{m}}_{H2O_{\mathit{out}}}{h}_{H2O_{\mathit{out}}}-{\dot{m}}_{H2O}{h}_{H2O}$$

By defining: $$c_{\mathit{pu}}\triangleq {\left(\frac{\partial h}{\partial t}\right)}_x=c_{\mathit{pa}}+x\cdot c_{\mathit{pv}}$$ and $$h_v\triangleq r_0+c_{\mathit{pv}}\cdot t$$ the following developments are possible (introducing Eq, (2), Eq. (7) and Eq. (8) in Eq. (6)): $$\begin{array}{l}\begin{array}{c}{Q}_1^{-}={\dot{m}}_a{c}_{\mathit{pu}}\left(t_{\mathit{steam}2}-t_{\mathit{steam}}\right)+{\dot{m}}_a{h}_v\left(x_{\mathit{steam}2}-x_{\mathit{steam}}\right)+{\dot{m}}_{H2O}\left(h_{H2O_{\mathit{out}}}-h_{H2O}\right)+{\dot{m}}_a{h}_{H2O_{\mathit{out}}}\left(x_{\mathit{steam}}-x_{\mathit{steam}2}\right)\\ Q_1^{-}={\dot{m}}_a\mathrm{\Delta }{h}_{\mathit{sensible}}+{\dot{m}}_a\mathrm{\Delta }{h}_{\mathit{latent}}+{\dot{m}}_{H2O}\left(h_{H2O_{\mathit{out}}}-h_{H2O}\right)+{\dot{m}}_a{h}_{H2O_{\mathit{out}}}\left(x_{\mathit{steam}}-x_{\mathit{steam}2}\right)\end{array}\\ Q_1^{-}=Q_s^{-}+Q_{\lambda }^{-}+{\dot{m}}_{H2O}\left(h_{H2O_{\mathit{out}}}-h_{H2O}\right)+{\dot{m}}_a{h}_{H2O_{\mathit{out}}}\left(x_{\mathit{steam}}-x_{\mathit{steam}2}\right)\end{array}$$ where:

• $Q_1^{-}$ is the heat flow at the walls;
• $Q_s^{-},$ $Q_{\lambda }^{-}$ are the fractions of sensible and latent energies of the flow of humid air;
• ṁ_H2O(h_H2Oout - h_H2O) is the Energy fraction of the liquid;
• ṁ_ah_H2Oout(x_steam - x_steam2) is the Energy fraction of the condensed water.

FIG. 7 depicts the complete Carrier diagram of the humid air for the first control region 405. The point on the diagram indicated as 1 corresponds to the state of the flow of vapors upon entering into the first control region; the point indicated as 2 corresponds to the state of the flow of vapors upon exiting the first control region. As can be appreciated looking at the diagram, the state of the flow of vapors exiting the first control region is rather close to the state indicated as s on the diagram, corresponding to the saturation condition (with relative humidity φ equal to 100%): thus, by spraying cooling water into the first control region, the temperature of the vapors decreases, and the relative humidity φ increases, but the specific humidity x decreases (because the flow of vapors exiting the first control region has a lower content of humidity).

Coming to the second control region 410, FIG. 8 depicts the respective humid air Carrier diagram. The point 2 on the diagram represents the starting state of the flow of vapors upon entering into the second control region (it corresponds to the point 2 on the Carrier diagram of FIG. 7).

The balance equations are: $${\dot{m}}_{\mathit{door}}{h}_{\mathit{door}}+{\dot{m}}_{\mathit{engine}}{h}_{\mathit{engine}}+{\dot{m}}_{\mathit{steam}2}{h}_{\mathit{steam}2}={\dot{m}}_{\mathit{final}}{h}_{\mathit{final}}==\left({\dot{m}}_{\mathit{door}}+{\dot{m}}_{\mathit{engine}}+{\dot{m}}_{\mathit{steam}2}\right)h_{\mathit{final}}$$ $${\dot{m}}_{\mathit{door}}{x}_{\mathit{door}}+{\dot{m}}_{\mathit{engine}}{x}_{\mathit{engine}}+{\dot{m}}_{\mathit{steam}2}{x}_{\mathit{steam}2}={\dot{m}}_{\mathit{final}}{x}_{\mathit{final}}=\left({\dot{m}}_{\mathit{door}}+{\dot{m}}_{\mathit{engine}}+{\dot{m}}_{\mathit{steam}2}\right)x_{\mathit{final}}$$ where Eq. (10) is the energy balance equation and Eq. (11) is the mass balance equation.

Dividing the two equations above for ṁ_final it follows: $$h_{\mathit{final}}=\frac{{\dot{m}}_{\mathit{door}}}{{\dot{m}}_{\mathit{final}}}{h}_{\mathit{door}}+\frac{{\dot{m}}_{\mathit{engine}}}{{\dot{m}}_{\mathit{final}}}{h}_{\mathit{engine}}+\frac{{\dot{m}}_{\mathit{steam}2}}{{\dot{m}}_{\mathit{final}}}{h}_{\mathit{steam}2}$$ $$x_{\mathit{final}}=\frac{{\dot{m}}_{\mathit{door}}}{{\dot{m}}_{\mathit{final}}}{x}_{\mathit{door}}+\frac{{\dot{m}}_{\mathit{engine}}}{{\dot{m}}_{\mathit{final}}}{x}_{\mathit{engine}}+\frac{{\dot{m}}_{\mathit{steam}2}}{{\dot{m}}_{\mathit{final}}}{x}_{\mathit{steam}2}$$

The state of the flow of vapors, in the second control region, moves from point 2 to point 4, which represents the state of the flow of vapors exiting the second control region. Points 5 and 6 represent the states of the flows of hot and dry air entering into the second control region and that are mixed with the flow of vapors: both are characterized by a low relative humidity φ).

The third control region is the union of the first and second control regions 405 and 410. The energy and mass balance for the third control region can thus be obtained from the above equations. The result is that the variables related to the common surfaces to the first and second control regions are eliminated, i.e. ṁ_steam2h_steam2, and ṁ_steam2x_steam2 (ṁ_steam2 = ṁ_a).

At the end, the flow of vapors exiting the second control region has a relatively low content of humidity.

FIG. 9 is a simplified flowchart illustrating a possible way of operation of the oven 100 according to an embodiment of the present invention.

When the oven 100 is started, the oven control unit 423 reads the operation selected by the oven user (block 905). The oven control unit 423 then decides whether or not the oven user has selected and started a cooking operation (decision block 910). If the oven user has not decided to start a cooking operation (exit branch N of decision block 910), the operation flow jumps back to block 905. If instead the oven user has selected and started a cooking operation (exit branch Y of decision block 910), the oven control unit 423 obtains information about the type of cooking selected by the oven user (block 915).

Then, depending on the type of cooking selected by the oven user, the oven control unit 423 decides whether or not the air propeller 180 is to be activated (block 920). If yes, the air propeller 180 is activated, if not, the air propeller 180 is kept off.

Still based on the type of cooking selected by the oven user, the oven control unit 423 determines (block 921) at which pre-set temperature of the vapors entering the vapor exhaust tower 155, the electrovalve 420 is to be activated to enable the intake of cooling water; such determination made by the control unit 423 may be carried out exploiting a database of parameters database, from which the oven control units 423 picks at which pre-set temperature of the vapors entering the vapor exhaust tower 155. Then, by exploiting the readings of the temperature sensor 425, the oven control unit 423 monitors the temperature of the vapors leaving the oven chamber 105 (block 923). In particular, the oven control unit 423 checks if such temperature is over the pre-set intervention temperature (block 925).

Until the temperature of the vapors leaving the oven chamber 105 and entering into the vapor exhaust tower 155 remains below the pre-set intervention temperature (exit branch N of decision block 925), the oven control unit 423 checks whether the cooking process is terminated (decision block 930): if the oven control unit 423 determines that the cooking process is terminated (exit branch Y of decision block 930), the oven control unit 423 checks (decision block 931) if the electrovalve 420 is currently open: in the affirmative case (exit branch Y of decision block 931) the electrovalve 420 is closed (block 933); after closing the electrovalve 420 (or leaving it closed, if it was already closed - exit branch N of decision block 931), the oven control unit 423 checks (decision block 935) whether the fan 180 is running: in the affirmative case (exit branch Y of decision block 935), the fan 180 is left running for a predetermined time after the end of the cooking process, whereas if the fan 180 is not running (exit branch N of decision block 935) the oven control unit 423 activates the fan 180 (block 940) for a predetermined time. The operation flow then jumps back to block 905. If the oven control unit 423 determines that the cooking process has not terminated yet (exit branch N of decision block 930), the oven control unit 423 checks whether the electrovalve 420 is activated (decision block 943): in the negative case (exit branch N of decision block 943), the operation flow returns to block 923, where the oven control unit 423 obtains a new reading of the temperature sensor 425; if instead the oven control unit 423 assesses that the electrovalve 420 is activated (exit branch Y of decision block 943), the oven control unit 423 de-activates the electrovalve 420 (block 945) and then the operation flow returns to block 923.

Let now be supposed that the temperature of the vapors leaving the oven chamber exceeds the pre-set temperature (decision block 925, exit branch Y): the oven control unit 423 activates the electrovalve 420 (block 950); cooling water thus starts to be sprayed by the nozzle 415 into the exhaust tower bottom section 405, to cool the vapors exiting the oven chamber 105.

The oven control unit 423 then determines whether the cooking process has terminated (decision block 955): if not (exit branch N of decision block 955), the operation flow jumps back to block 923 (where the oven control unit 423 obtains a new reading of the temperature sensor 425; if instead the oven control unit 423 determines that the cooking process has terminated (exit branch Y of decision block 955), the oven control unit 423 obtains (through the temperature sensor 425) the temperature of the vapors entering into the vapor exhaust tower 155 (block 960), and then the oven control unit 423 checks whether the temperature of the vapors exceeds the pre-set intervention temperature (decision block 965): until the vapors temperature stays above the pre-set intervention temperature (exit branch Y of decision block 965), the electrovalve 420 is kept open, and the oven control unit 423 continues to monitor the vapor temperature. When the vapor temperature falls below the pre-set intervention temperature (exit branch N of decision block 965) the electrovalve 420 is closed (block 933) and the same operations described above (blocks 935 and 940) are performed. The operation flow returns to block 905.

In other words, the injection of cooling water into the exhaust tower bottom section 405 (i.e., into the first control region of the vapor exhaust system) is selectively enabled based on an assessment of the temperature of the vapors that leaves the oven chamber 105 and enters into the vapor exhaust tower. Also the activation of the fan 180 is selective, depending on the cooking process.

The vapor exhaust system according to the described embodiment of the present invention comprises a sinuous, tortuous, labyrinthic vapors conduit arranged vertically, into which cooling water can (selectively) be injected. The tortuous shape of the conduit, thanks to the depression generated by a fan downstream the first control region (in the shown example, the fan 180) allows exploiting the inertia of the particles of vapor/fat, pushing them against the baffles 177 (in particular, against the first ones, proximate to the bottom of the exhaust tower bottom section 405). The spray of nebulized cooling water allows capturing the finest particulate (and this effect is also promoted by the baffles 177 proximate to the top of the exhaust tower bottom section 405, which are cooled down by the water spray).

Experimental trials carried out by the Applicant have shown that the temperature of the vapor flow exiting the vapor exhaust system according to the described embodiment of the present invention, also in critical operating conditions (oven chamber temperature set to 250 °C and 100% of humidity), did not exceed 30 °C at a relative humidity of 25% (with 19 °C of ambient air temperature).

In FIG. 10 there is depicted, schematically as in FIG. 4, a vapor exhaust tower according to a slightly different embodiment of the present invention; components, parts and elements that are identical, similar or equivalent to those described in connection with the previous embodiment are denoted with same reference numerals. A difference of the embodiment of FIG. 10 compared to the previous embodiment resides in that at least part (one, more than one, possibly all) of the baffles 177, like the baffles 1077 visible in the figure, are hollow at their interior and arranged to be run through by a relatively cold heat-exchange fluid 1005 (e.g., liquid, like water), which receives heat released from the vapors passing through the first control volume 405. In this way, the heat released by the vapors leaving the oven chamber can be at least partly collected by the heat-exchange fluid, instead of being only dissipated.

Another difference in the embodiment of FIG. 10 compared to the previous embodiment is the different position of the nozzle 415 (which in this embodiment is not at the top of the first control region) and of the temperature sensor 425 (which in this embodiment is not at the bottom of the first control region). In particular, differently from the previous embodiment, in this embodiment the nozzle 415 is associated to a lower portion of the bottom section 405 with respect to the temperature sensor 425.

In FIG. 10 just one opening in the exhaust tower top section 410 is shown; this single opening may schematize the two openings 433 and 435 of the previous embodiment, but it might also be possible that through such single opening both of the two cooling air fluxes enter into the vapor exhaust tower. In still other embodiments, one of the two cooling air fluxes might be absent.

Also with the vapor exhaust tower of the embodiment of FIG. 10, the oven 100 may operate as described in connection with the previous embodiment (flowchart of FIG. 9).