EP2191205A2 - Baking oven with an air outlet opening - Google Patents

Abstract

The invention relates to a baking oven with a baking space, which is provided with an outlet opening, through which the gases can escape from the baking space. It is an object of the present invention to ensure constant baking conditions while avoiding the mixing of air from the surroundings with the outflowing gases. This objective is accomplished owing to the fact that a throttle element (7) for varying the flow cross section for the outflowing gases is disposed in the area of the outlet opening and coupled with a driving mechanism (8) controlled by a regulating module (9), and that a first pressure sensor (12), which is connected with the control module (9), is disposed on the side of the throttle element (7) facing the baking space.

Description

 PatXML 1/12 M078PC0706

description

Oven with air outlet Technical area

The invention relates to an oven with a baking chamber, which is provided with an outlet opening, can escape through the gases from the oven. It further relates to a method for operating a baking oven.

State of the art

Ovens usually have a heater, are heated by the air and / or steam as the heating medium to the temperature required for baking (usually considerably above 100 ° C). The gaseous heating medium, in particular also the vapor resulting from caking, after a certain time passes outwardly through the outlet opening from the baking chamber of the oven. Conventional ovens are designed so that there is a negative pressure of approximately 0.1 mbar (10 Pa) at the outlet. This low vacuum ensures optimum operating conditions during baking, with the heated and humidified atmosphere remaining in the oven for a sufficient period of time to prevent the baked goods from drying out.

In the prior art, the train in the air outlet opening, ie the value of the negative pressure relative to the ambient pressure, achieved by the construction of the furnace and the adjoining the air outlet opening chimney. In modern ovens, the pipe for discharging the gases from the baking chamber is provided with a draft control flap, which opens to the environment. If the overpressure is too great, the draft control flap allows the inflow of ambient air into the chimney or into the pipe carrying the exhaust air and exhaust gases out of the oven. The draft control valve has a certain opening resistance, so that it opens at a certain negative pressure of the outflowing gases. In this way, the negative pressure at the outlet opening for the heating medium can be adjusted to a constant value in adaptation to the installation situation of the oven. By the PatXML 2/12 M078PC0706

however, ambient air changes the steam significantly its physical properties. In particular, the recoverable from the steam energy decreases.

Presentation of the invention

The object of the present invention is to ensure the constant baking conditions while avoiding the admixture of ambient air to the outflowing gases.

This object is achieved in relation to the oven according to the invention in that in the region of the outlet opening, a throttle element is arranged for varying the flow cross-section for the outflowing gases, which is coupled to a regulated by a control module drive, and that on the back room lying side of the throttle element, a first pressure sensor is arranged, which is connected to the control module. As a throttle element can be used in practice, a throttle valve.

In other words, the draft control flap is moved into the flow cross-section for the outflowing gases. It no longer releases an opening leading to the environment as in the prior art. Instead, it changes the flow resistance of the gases in the channel carrying the outflowing gases.

This makes it possible, the negative pressure in the region of

Dynamically control the outlet opening for the heating medium from the baking chamber. A possible type of control is the setting of a constant negative pressure of 10 Pa compared to the ambient pressure. This value, which has already been preferred in the past, can be set reliably by the control loop, in which the pressure in the baking chamber or shortly before the throttle element is determined. The admixture of ambient air, which reduces the saturation of the vapor in the exiting heating gas and thereby causes the dew point to drop, is not necessary for maintaining a constant underflow value at the outlet opening.

A need for such a setting arises in particular when the withdrawal conditions are variable behind the outlet opening. In PatXML 3/12 M078PC0706

In modern bakeries, the heating medium emerging from the baking chamber is often not simply released into the atmosphere. The heating medium can be used for the treatment of warm water or for other heating purposes. To this end, often joins the oven to an energy recovery module. Such energy recovery module is known for example from the German utility model DE 297 09 784 U1 and DE 20 2006 003 153 U 1. Often several ovens in a bakery are connected to a common energy recovery module.

The energy recovery module generally has a fan to ensure the reliable transport of the emerging from the oven heating medium through the energy recovery module therethrough. The negative pressure at the outlet thus depends on the fan power. If several ovens are connected in parallel and are coupled to an energy recovery module via a common piping for the exiting heating medium, they interact with each other. The flow situation at the exit opening of each one of the ovens can vary widely depending on the amount of hot gases from the other ovens and depending on the operating point of the energy recovery module. Thus, fluctuations in the negative pressure in the region of the outlet opening of a baking oven can result from the fact that several more, coupled to the same energy recovery module ovens, are switched on or off. But there are also variations in the negative pressure at the air outlet openings by atmospheric influences, e.g. Wind blowing into the opening of the fireplace is possible.

By proposing a pressure measurement in the lying on the side of the baking chamber area before the throttle element and a pressure control by adjusting the throttle element as a function of the detected measured value, it is possible to achieve a predetermined constant negative pressure value independently of the operating points of coupled ovens , The throttle element varies the flow cross-section in the channel for the from the baking chamber PatXML 4/12 M078PC0706

escaping gases and thus allows the adjustment of the pressure in the region of the outlet opening. This also applies if the oven is not coupled to a power recovery module, but its air outlet is connected directly to the fireplace.

In practice, may be arranged on the lying outside the baking chamber side of the throttle element, a second pressure sensor which is connected to the control module. This second pressure sensor measures substantially the ambient pressure and is therefore preferably mounted on the outside of the furnace housing or the tube for the exiting heating gas. The second pressure sensor may be formed in practice from the second side of a diaphragm of a differential pressure sensor. The first side of the diaphragm of the differential pressure sensor forms the first pressure sensor. In this way, the differential pressure sensor provides a signal which the differential pressure between the outlet opening of the oven and the environment.

Alternatively, it is possible to measure the difference between the pressure on the baking chamber side facing the throttle element and the pressure on the side remote from the baking chamber side of the throttle element. In this case, however, the pressure difference between the pressure on the side facing away from the baking chamber of the throttle element and the environment should be known, because to achieve optimum baking results, the correct adjustment of the pressure difference between the pressure in the outlet opening and the ambient pressure is relevant. When using energy recovery modules often the pressure difference between the pressure on the side facing away from the back chamber of the throttle element and the environment is known, because this is detected by pressure gauge of the energy recovery module, so that here the pressure difference measurement via the throttle valve a simple and effective Procedure represents.

Furthermore, it may be useful in certain applications, not to select the ambient pressure but the pressure directly behind the Drosseklappe as a reference value. In this case, the static pressure measured immediately after the throttle valve becomes the second pressure sensor PatXML 5/12 M078PC0706

fed.

The control module may be configured such that it forms from the measured value of the second pressure sensor and the measured value of the first pressure sensor, a difference value which is used for the control of the drive for the throttle element. This differential pressure between ambient pressure and pressure in the region of the air outlet opening is decisive for the flow velocity of the heating medium within the baking chamber and through the air outlet opening.

As already mentioned, the control module can regulate the throttle element such that a constant difference value is maintained. The control module can also regulate the throttle element to a variable difference value. For example, it may be desirable at certain times of a baking program for certain dough pieces that the baking atmosphere remains unchanged over a longer period of time. This can e.g. immediately after humidifying the oven with superheated steam. If a hot steam is supplied to the baking chamber, it may be advantageous for the baking result if the high humidity is kept for as long as possible. In this case, the control module can regulate the throttle element such that the air outlet is closed. At other times of the baking program, a particularly fast exchange of the baking atmosphere may be desired. For example, a quick change of the baking temperature at a certain time of the baking program can be beneficial. This can be achieved in that the throttle valve is fully opened and thereby a maximum pull in the air outlet opening of the oven is achieved.

As a throttle element, in particular a pivotable throttle or a linearly displaceable slide can be used. Throttles are already installed ready installed in pipe sections, where they are provided with electric drives and differential pressure measuring devices. The differential pressure gauges measure the difference between the pressure immediately before the throttle and immediately after the throttle PatXML 6/12 M078PC0706

Throttle. However, the pressure value immediately behind the throttle valve may be influenced by the flow velocity of the medium in the region of the throttle valve. Therefore, for the value of the ambient pressure, it is preferable to arrange an external pressure sensor, for example, on the housing of the furnace.

The invention further relates to a method for operating a baking oven with a baking chamber, which is provided with an outlet opening, can escape through the gases from the oven.

To solve the above-explained object, a arranged in the region of the outlet opening throttle element is operated with a controlled by a control module drive for varying the flow cross-section for the outflowing gases, and a first pressure sensor, which is disposed on the side lying to the baking chamber of the throttle element is, passes a measurement signal to the control module. The measuring signal can be transmitted either electrically via a pressure line or via a converter, which converts the detected pressure value into an electrical quantity, and an electrical conductor.

On the basis of the detected measured value may be any

Negative pressure in the region of the air outlet opening can be adjusted by the control module.

In practice, a second pressure sensor on the outside of

Backspace lying side of the throttle element conduct a measurement signal to the control module. Preferably, the control module from the measured value of the second pressure sensor and the measured value of the first pressure sensor forms a difference value which is used for the control of the drive for the throttle element.

As mentioned above, the control module can regulate the throttle element such that a constant difference value is maintained. Alternatively, a variable difference value can be achieved, which assumes specific values over the time of the baking program.

The exiting through the outlet opening air can to a

Energy recovery module are routed. The outlet opening of the oven can be substantially tight by the throttle element PatXML 7/12 M078PC0706

be closed. In this way, the negative pressure in the region of the air outlet opening can be set to virtually zero.

Brief description of the drawings

An embodiment of the invention will be described below with reference to the accompanying drawings.

Fig. 1 shows an oven according to the invention with energy recovery module.

Fig. 2 shows a sectional front view of the adjoining the outlet opening pipe section in which the throttle element is arranged.

FIG. 3 shows a side view of the throttle element from FIG. 2.

Embodiment (s) of the invention

In Fig. 1, a craft baking oven 1 can be seen, which has a

Exhaust pipe 2 is coupled to an energy recovery module 3. The oven 1 consists of a thermally insulated wall, which delimits the oven. Other components of the oven 1 such as heater, blower, steam generator, oven control, etc. are not shown in the drawings.

At an upper rear corner of the oven 1, an outlet opening 4 is arranged, to which a pipe socket 5 is connected. Through the pipe socket 5, the medium in the oven chamber of the oven 1, in particular the heated air and heated water vapor, escape from the oven. The heating medium emerging from the baking chamber through the pipe socket 5, in particular the hot steam, is led through the exhaust pipe 2 to the energy recovery module 3, where thermal energy is removed from the gaseous medium via heat exchangers. The thermal energy is used in particular for heating domestic water. For ovens that are heated with oil burners or gas burners, the energy recovery module can also be fed with the burner's hot flue gas. This gas is released from toxins in a flue gas scrubber. Furthermore, it is also deprived of thermal energy for heating service water. As mentioned, the function is PatXML 8/12 M078PC0706

of such an energy recovery module described for example in German Utility Model DE 297 09 784 U1.

On the pipe socket 5, a pipe section 6 is placed, which is flowed through by the gases emerging from the baking chamber and in which a throttle valve 7 is received as a throttle element. The pipe section 6 with the throttle valve 7 is shown in detail in FIGS. 2 and 3. The rotational position of the throttle valve 7 is adjusted by an electric drive motor 8 and changes the flow cross section for the exiting gases.

The drive motor 8 is controlled by a flanged control module 9. The control module 9 has two signal inputs 10,11. These signal inputs 10,11 can be fed signals from pressure sensors. The first pressure sensor 12 (see FIG. 3) is arranged upstream of the throttle flap 7 in the flow direction. The pressure sensor 12 essentially measures the pressure prevailing at the outlet opening of the baking chamber.

The second pressure sensor 13 is connected via a pressure line 14 to the environment. In other words, the second pressure sensor 13 detects the pressure values of the air surrounding the oven. This pressure value is independent of the suction that is generated from the energy recovery module 3 via the exhaust pipe 2 in the area behind the throttle valve 7. As mentioned above, alternatively, the pressure value directly behind the throttle valve may be supplied to the second pressure sensor.

In this way it is possible to set a constant in relation to the ambient pressure in the region of the outlet opening 4 of the oven 1.

As mentioned, in practice a plurality of ovens 1 can be connected to an energy recovery module 3. The throttle valve 7 allows a constant adjustment of the negative pressure in the region of the outlet opening 4 of each of these furnaces, regardless of the operating parameters of the other furnaces and independent of the operating parameters of the energy recovery module. 3 PatXML 9/12 M078PC0706

If the throttle valve 7 is pivoted into the position perpendicular to the tube axis, the tube cross-section is substantially sealed. In this way, escape of the atmosphere into the oven 1 can be completely prevented in certain phases of the baking program.

Similarly, if required, an increased outflow of gases from the oven 1 can be promoted by the throttle valve 7 is pivoted in a pipe axis intersecting plane. This results in a low flow resistance through which e.g. a particularly rapid exchange of the atmosphere in the baking chamber of the oven, e.g. to lower the temperature, can be achieved.

It should be noted that the drawings merely illustrate the invention, but do not limit its scope. Instead of the throttle valve 7, any suitable throttle element can be used. For example, a slider can be used, which covers the cross-section of the pipe section 6 more or less. Also can be used as a throttle element, a dazzle-like tube closure with which the flow cross-section can be varied.

In particular, for the realization of temporally variable negative pressures in the region of the outlet opening 4 of the oven, the control module 9 can be coupled to the control of the oven. The baking oven control gives the control module 9 different desired pressure values as a function of the baking program. The desired pressure values preferably define differential pressures, i. the value of the negative pressure prevailing in the region of the outlet opening 4 with respect to the atmosphere surrounding the furnace.

[0038] List of Reference Numerals

1 oven

2 exhaust pipe

3 energy recovery module

4 outlet opening

5 pipe sockets

6 pipe section PatXML 10/12 M078PC0706

7 throttle element, throttle

8 drive motor

9 control module

10 signal input

11 signal input

12 first pressure sensor

13 second pressure sensor

14 signal line

Claims

PatXML 1 1/12 M078PC0706 claims 1. oven (1) with a baking chamber, which is provided with an outlet opening (4) through which gases can escape from the baking chamber, characterized in that in the region of the outlet opening (4) a throttle element (7) for varying the flow cross section for the outflowing gas is arranged, which is coupled to a drive (8) controlled by a control module (9), and that a first pressure sensor (12) is arranged on the side of the throttle element (7) lying to the baking chamber, which is connected to the control module ( 9) is connected. 2. oven (1) according to claim 2, characterized in that on the outside of the baking chamber side of the throttle element (7), a second pressure sensor (13) is arranged, which is connected to the control module (9). 3. oven (1) according to claim 2, characterized in that the control module (9) is configured such that it forms from the measured value of the second pressure sensor (13) and the measured value of the first pressure sensor (12) a difference value which for the Control of the drive (8) for the throttle element (7) is used. 4. oven (1) according to claim 3, characterized in that the control module (9) controls the throttle element (7) such that a constant difference value is maintained. 5. oven (1) according to claim 3, characterized in that the control module (9) controls the throttle element (7) such that a variable difference value is achieved, which assumes predetermined values over the time of a baking program. 6. oven (1) according to one of the preceding claims, characterized in that the outlet opening (4) leads to an energy recovery module (3). 7. oven (1) according to one of the preceding claims, characterized in that the throttle element is a throttle valve (7) or a slide. 8. A method for operating a baking oven (1) with a baking chamber, which is provided with an outlet opening (4), by the gases from the baking chamber PatXML 12/12 M078PC0706 can escape, characterized in that for varying the flow cross-section for the outflowing gases in the region of the outlet opening (4) arranged throttle element (7) with a controlled by a control module (9) drive (8) is actuated and that a first pressure sensor (12 ) on the back of the baking chamber side of the throttle element (7) passes a measurement signal to the control module (9). 9. The method according to claim 8, characterized in that a second pressure sensor (13) on the outside of the baking chamber side of the throttle element (7) passes a measurement signal to the control module (9). 10. The method according to claim 9, characterized in that the control module (9) from the measured value of the second pressure sensor (13) and the measured value of the first pressure sensor (12) forms a difference value for the control of the drive (8) for the throttle element (7) is used. 11. The method according to claim 10, characterized in that the control module (9) controls the throttle element (7) such that a constant difference value is maintained. 12. The method according to claim 10, characterized in that the control module (9) controls the throttle element (7) such that a variable difference value is achieved, which assumes predetermined values over the time of a baking program. 13. The method according to any one of claims 8 to 12, characterized in that the through the outlet opening (4) exiting gases to an energy recovery module (3) is passed. 14. The method according to any one of claims 8 to 13, characterized in that the outlet opening (4) through the throttle element (7) can be sealed substantially.