ITPD20100163A1 - COOKING OVEN FOR FOODS WITH A MEASUREMENT DEVICE FOR THE FLOW OF THE GAS OUTLET FROM THE OVEN AND MEASUREMENT METHOD WITH WHICH THE DEVICE OPERATED AS A DEVICE - Google Patents

Description

DESCRIPTION

The present invention refers to a cooking oven for foods with a device for measuring the flow rate of the gases leaving the oven, having the characteristics set out in the preamble of the main claim n.1. The invention is also directed to a measurement method with which the aforementioned device operates, for measuring the flow rate of the gases leaving the furnace.

The invention is located in the specific technical field of cooking ovens for food, typically equipped with a device for producing or introducing water steam and / or a device for introducing ambient air into the cooking chamber of the oven as well as © provided with a hole that connects the cooking chamber with the external environment for the escape of gas and vapors introduced and / or produced inside the cooking chamber. The introduction or production of water vapor and / or ambient air is used in `` steam '' cooking (maximum concentration of water vapor) or those in which a concentration of steam is required. ™ controlled water. In fact, during these cooking operations there is the need to introduce or produce water steam and / or to introduce ambient air into the cooking chamber to regulate the concentration of the water vapor itself. This introduction or production of steam or ambient air, together with the possible production of water vapor by the food itself, causes gas to escape from the hole that connects the oven chamber with the external environment. The gas that escapes can consist of:

- 100% water steam, in case you are cooking with 100% steam or if the food to be cooked contains a high amount of water that evaporates during cooking, or from

- a mixture of water vapor and air, in case you are cooking with a concentration lower than 100% and / or you are introducing ambient air into the oven to decrease the concentration of water vapor inside .

Furthermore, depending on the type of cooking, other substances also escape together with the gas, for example vapors of organic substances such as fats that develop during cooking.

In order to control the flow of steam of water introduced or produced and / or the flow of ambient air introduced into these cooking ovens, it would be convenient to be able to measure the flow of gas coming out of the cooking chamber and use this signal to regulate the means for introducing air and introducing or producing water vapor in the oven chamber.

In particular in `` steam '' cooking where the concentration of water vapor must be the maximum, adjusting the flow of water steam introduced or produced in the cooking chamber to the minimum necessary, would allow great energy savings. due to the high thermal power necessary for the production of excess steam. In fact, in these cases, current practice provides for a production of steam much higher than the minimum necessary.

Unfortunately, this measurement is made very complicated by the high temperatures of the gas that comes out of the cooking chamber and its ability to easily dirty and / or clog many flow rate measuring devices, due to the mainly organic substances that are produced during cooking. Devices and / or methods are known which measure this flow rate directly or indirectly but have numerous disadvantages including cost, reliability and precision.

The problem underlying the present invention is that of providing an oven with a measuring device structurally and functionally conceived to obviate the limits highlighted with reference to the cited known art.

The problem is solved by the invention by means of an oven with a measuring device and a method for measuring the flow rate of the gases leaving the oven, made in accordance with the attached claims.

Further characteristics and advantages of the invention will become clearer from the detailed description which follows of a preferred example of embodiment illustrated, by way of non-limiting example, with reference to the accompanying drawings in which:

- figure 1 is a schematic view of an oven provided with a device for measuring the flow rate of the gases leaving the oven, in accordance with the present invention,

- figure 2 is a schematic view of a detail of figure 1 in a possible embodiment variant.

- figure 3 is a schematic view of a detail of figure 1 in a possible further embodiment variant.

With reference to the aforementioned figures, 1 denotes, and only schematically represented, a food oven provided with a cooking chamber 2 inside which the food to be cooked can be accommodated.

The oven is provided with heat generation means, not shown, for example including electric resistances or a heat exchanger connected to a combustible gas burner. Means for generating or introducing water steam or for decreasing its concentration (not shown) are also provided, for example by introducing water steam produced by a steam generator outside the cooking chamber or the conveyance of water inside the cooking chamber in order to increase the concentration of water vapor suitable for the cooking process or by introducing ambient air inside the cooking chamber in order to reduce it concentration.

With 3 is indicated a pipe communicating with the inside of chamber 2, through a hole 3a, which connects said chamber with the external environment to convey the gases generated in the chamber following the introduction to the outside. o production in the chamber itself of water vapor or ambient air together with the possible production of water vapor by the food itself during the cooking process. It should be noted that depending on the type of cooking, other substances also escape through the pipe 3 together with the gases, for example vapors of organic substances such as fats which develop during cooking.

More specifically, the pipe 3 has a â € œTâ € conformation with a first section 4, exiting the chamber 2, which is prolonged in a second and third section 5, 6, developed as an extension of one of the Other, as clearly illustrated in figure 1. Gases are expected to escape from the free end of section 6. In section 5 a second pipe 7 is inserted, with a smaller diameter than the diameter of section 6 of pipe 3. Said pipe 7 is extended beyond the central connection node of sections 4-6, up to an area of section 6.

The gas passage section between the pipe 6 and the pipe 7 represents a narrowing of the passage section of the pipe 7, this narrowing extending up to the end 7a of the pipe 7, beyond which the passage section returns to assume the size section of section 6 of piping 3.

The aforesaid section narrowing creates a static device in which an increase in speed is generated (in the narrow section) associated locally with a corresponding decrease in the pressure of the gas flowing through said device.

Thanks to the depression, preferably made with pressure values lower than atmospheric pressure, which is created at the end 7a of the pipe 7, due to the increase in gas speed (caused by the narrowing of the section) a flow of ambient air is sucked in by the opposite end 7b of pipe 7, open to the external environment. This flow of ambient air which is sucked along the pipe 7 can be easily measured, for example through a flow meter 8, only schematically represented, positioned on the pipe 7.

In practice, the static device exploits the well-known principle called the Venturi effect (the pressure of a fluid current increases with decreasing speed and vice versa). In fact, it is known to use the Venturi tube to measure the flow rate of a fluid by measuring the pressure of the fluid itself in two points of the tube with different sections / speeds. If a Venturi tube made with a geometry such as to create a pressure lower than the atmospheric one in the area in which there is an increase in speed is inserted in the exhaust pipe 3 of the gases coming out of the cooking chamber 2 of the oven and is connected to this zone 7 open to the atmosphere, there will be a passage of air from the environment towards the inside of the Venturi tube.

For a certain

- geometry of the Venturi tube and of the pipe that connects the depression area of the Venturi tube with the environment,

- temperature T (equal to that of cooking chamber 2) and water vapor concentration C of the gas passing through the Venturi tube,

- Tâ € ™ temperature and pâ € ™ atmospheric pressure,

there is a one-to-one correlation between the flow of gas coming out of the cooking chamber 2 and the flow of air sucked in by the Venturi tube. The correlation that binds the flow rate of aspirated ambient air and the flow rate of gas leaving the oven can be determined both theoretically (using the known relationships that describe these phenomena, for example Bernoulli's law, the universal law of gases, etc. ) and experimentally. Once the correlation between the ambient air flow and the gas flow rate has been determined as the aforementioned variables vary, the gas flow rate can be determined by measuring the ambient air flow rate.

Conveniently, sensor means (not shown) can also be provided for measuring the concentration C of water vapor in said chamber and / or the temperature T of the cooking chamber and / or the ambient temperature Tâ € ™ and / or the pressure atmospheric pâ € ™.

It is also understood that the static device can assume alternative configurations with respect to that illustrated in figure 1. For example, a Venturi tube in the configurations illustrated in figures 2 and 3 can be chosen as a possible variant of construction.

Furthermore, it can also be envisaged that a modest flow rate Qâ € ™ of ambient air is forced into pipe 7, for example by means of a ventilation device (not shown), independently of the presence or absence of gas leaving the cooking chamber. 2. In this case, in the presence of gas leaks, the flow of air sucked in thanks to the vacuum induced by the static device is added to the flow rate Qâ € ™. Said flow rate Qâ € ™ can be easily determined, as it is correlated to the characteristic curve of the ventilation means (for example proportional to the rotation speed of a fan with which the ventilation means is made).

In the operation of the device for measuring the flow rate of the gases leaving the furnace, the method with which it operates mainly involves measuring the flow of ambient air recalled, along the pipe 7, in the reduced pressure area of the static device through which they are conveyed the gases leaving the cooking chamber, and to obtain a measurement of the gas flow rate leaving the chamber through the correlation between said gas flow and the ambient air flow as a function of the geometry of the static device, the temperature, the pressure and water vapor concentration of the gases leaving the chamber.

The invention therefore solves the proposed problem, achieving numerous advantages.

A first advantage lies in the fact that the measured air flow is at room temperature and not at the temperature of the cooking chamber.

A second advantage is linked to the fact that the aspirated ambient air does not contain substances (for example cooking fats) that can dirty and / or clog the measuring device.

Another advantage is that the ambient air intake pipe remains clean because it is always in depression with respect to the point of the Venturi pipe to which it is connected.

Claims (6)

CLAIMS 1. Cooking oven for foods comprising a cooking chamber, means for introducing or producing water vapor in said cooking chamber and / or means for introducing ambient air into the cooking chamber, a first connection pipe of the cooking chamber with the external environment, for the escape of the gases and vapors introduced and / or produced in the cooking chamber, a device for measuring the flow rate of the gases leaving the cooking chamber, said chamber being under certain conditions of temperature, pressure and water vapor concentration, characterized by the fact that said measuring device comprises a static device inserted in said first pipe connecting the oven chamber with the external environment, said static device including an area with a narrow section able to create in correspondence of said section an increase in the speed of the gas with a consequent decrease in the pressure of the gas itself, and by the fact that d This device comprises a second pipe suitable for connecting the external environment with said restricted section area in which there is a decrease in pressure, through said second pipe ambient air being drawn in, capable of mixing with the gases conveyed out of the oven along the first pipe, the flow rate of the outgoing gases being correlated to the flow of air drawn along said second pipe, as well as to the conditions of pressure, temperature and concentration of water vapor existing inside said chamber. 2. Furnace according to claim 1, in which a device for measuring the flow rate of air flowing through said second pipe is provided on said second pipe, suitable for connecting the external environment with the reduced pressure zone of the static device. . 3. Furnace according to claim 1 or 2, wherein said static device is a Venturi tube. 4. Furnace according to claim 1, wherein in the zone of the static device at reduced pressure, the value of said pressure is lower than the atmospheric pressure. 5. Oven according to one of the preceding claims, in which sensor means are provided for measuring the water vapor concentration in said chamber and / or the temperature of the cooking chamber and / or the ambient temperature and / or the pressure of the cooking chamber. 6. Method for measuring the flow rate of the gases leaving the cooking chamber of a food oven equipped with a device for measuring said flow rate made in accordance with one or more of the preceding claims, the method comprising the steps of: - determining the flow rate of ambient air drawn, along said second pipe, in the reduced pressure zone of the static device through which the gases leaving the cooking chamber are conveyed, - obtain a measurement of the gas flow rate leaving the chamber through the correlation between said gas flow rate and the ambient air flow rate as a function of the geometry of the static device, the temperature, pressure and water vapor concentration of said gas leaving the chamber.