DK177820B1 - Method of controlling air intake and use - Google Patents

Abstract

The invention comprises a method for controlling and controlling the air flow (6, 6A, 6B, 6C) in buildings such as housing systems (1), based on the use of one or more mathematical algorithms, where the result of the algorithm calculations is used to control the air supply to the housing via a number of valves (5) for air intake. In a preferred embodiment, the method comprises an algorithm based on the use of a so-called corrected Archimedes number. The invention provides the remarkable advantage that the air flow (6, 6A, 6B, 6C) in a stable (1) can be continuously controlled and controlled automatically and kept optimally independent of changes in, for example, ambient temperature or weather conditions. The invention further comprises a valve (5) for air inlet, which is provided with a measuring probe for determining the air volume flow through the valve. This provides that the air intake valve (5) can be used to monitor the air supply to the stable (1) and thus provide the control algorithm with significant input parameters. Furthermore, the invention comprises the use of air intake valves (5) for housing systems (1). Thus, the invention can improve both animal welfare and the operating economy of a housing facility (1).

Description

Method of controlling air intake and use.

The invention relates to a method for controlling eg air flow in buildings such as housing facilities provided with one or more valves with adjustable opening area and an integrated volumetric flow meter for air intake and one or more active air outlets.

Furthermore, the present invention relates to the use of the method.

It is known to use climate control systems in stables.

In livestock livestock housing, the climate control system ensures a good climate for the animals. The temperature, humidity and CO 2 content of the stable air are essential for animal well-being and growth. But equally important to the welfare of the animals is the flow rate of the barn air, the flow pattern in the animals' living area, and how the fresh air is mixed with the air in the barn.

The climate control system consists of a ventilation system supplemented with systems for heating, cooling, wetting etc. The air flow in the barn is mainly controlled by the ventilation system. The animals release metabolic products to the stable air in the form of heat, water and CO 2. The metabolism products are removed by passing part of the air in the barn through the air outlets and fresh air from the surroundings is taken into the barn through the air inlets.

A typical example is a barn with air outlet in the roof of the building and air intake in the sides of the building. There can typically be 1 or 2 air inlets on each side of the building. The air outlets are active while the air moves in through the air inlets driven by the negative pressure that the active air outlets create in the stable relative to the surroundings. The degree of opening of the air intake can be varied so that a suitable vacuum can be maintained in both small and large air exchange in the stable. It is the air velocity at the return of the air intake and the temperatures of the air inside and outside the barn that essentially determines the air flow in the barn. The suppression in connection with the opening rate of the air intake determines the air velocity at the return. Therefore, the vacuum is used as an indicator of the air flow in the barn.

The existing climate control systems continuously regulate the temperature, humidity and CO2 content of the barn air during operation, while the air flow in the barn is regulated when the barn is put into operation - in principle once during the life of the climate system. Adjustment is made by adjusting the opening rate of the air inlets from the minimum air change to the maximum air change. The procedure prescribes which negative pressure must be set for a given air change. Finally, the air flow is controlled by supplying smoke at the air intake and considering the distribution pattern of the smoke.

An air intake is typically made up of several valves. The degree of opening of the valves can be changed. The valves, which together constitute an air intake, are operated simultaneously. The valves are located so close that the air jet from the valves inside the building can be considered as one unified air jet throughout the length of the air intake. A measurement has been made in advance to determine the air performance of the valve and the air velocity at the exhaust side of the valve as a function of the degree of opening and pressure drop across the valve. It is thus possible to calculate the total performance of an air intake with knowledge of the number of valves in the intake, suppressed in the building and knowledge of the degree of opening of the valves.

DE3873472 T2 discloses a method for controlling and regulating the air flow in a building provided with valves (1) for air inlet and active air outlet (13), where the control and regulation of air flow is effected by regulating dampers (2) in the valves, based on calculation of the ratio of a reference signal to the volume flow as an input parameter measured with a measuring probe integrated into the valves (8).

However, it has been found that there are some disadvantages of the prior art.

With the prior art, air flow is regulated in the barn when the barn is put into operation. Therefore, this adjustment is only optimal in relation to the weather folds on the day of the adjustment. During operation, the temperature is typically measured both outside and in the barn. Although these temperatures have a decisive influence on the air flow in the barn, the measurements are not used to continuously control the air flow.

With any building, due to the wind, there is a higher pressure on the wind side and a correspondingly lower pressure on the reading side. The pressure difference varies with the wind speed and the wind direction. On the windward side of the stable, the pressure drop across the air intake will be relatively large, and the air flow through the air intake and the air velocity at the return of the air intake will be correspondingly large.

Conversely, on the reading side of the building, there will be a relatively small pressure drop across the air intake, and therefore the amount of air and the air flow rate will be less. This results in there being no symmetry in the flow of air in the wind and reading side of the barn.

As the barn is used, there will be wear and tear on the air intake activation system or leaks may occur in the barn. As a result, the preconditions for balancing will no longer be present and the air flow will have changed from conditions during commissioning.

As mentioned before, the air inlets are adjusted when the housing is put into operation. This adjustment is done manually. Therefore, there is a need for a qualified service technician to adjust all the stalls that are put into operation.

In the article "Modeling Jet Drop Distance for Control and a Nonisothermal, Flap-Adjusted Ventilation Jet" by G. Zhang, S. Morsing and Power of the Transactions of the American Society and Agricultural Engineers, 1996, volume 39 (4), page 1421 -1431, discloses a technique for determining air flows in a stable building where air is passed through adjustable valves and discharged through an active air outlet. The technique uses a mathematical algorithm for the air flow determination, where a significant input to the algorithm is the air supply to the barn, which is calculated indirectly by measuring pressure / differential pressure in the barn.

However, this technique has not been used in practice, partly because the determination of the distribution between air intake of the total air supply to the stable is subject to unacceptable uncertainty.

It is therefore an object of the invention to improve the known method and technique below.

The object of the invention is met by a method of the type specified in the preamble of claim 1, characterized in that the control and regulation of the air flow is effected by regulating the valves for air intake, based on the application of an algorithm of the form:

where the valves are regulated so that

for TacTo, where

where preferably

Armin = 30 or so

for

where

where preferably

Armax = 73 where:

Arc is a corrected Arhimedes number, W [m] is the length of the building space, H [m] is the height of the building space, a [m] is the vertical extent of the air intake, b [m] is the horizontal extent of the air intake, q [m3 / s] is the volume flow through air intake,

Ts [° C] is the temperature of the air in the building space,

Ta [° C] is the temperature of the air outside the building space,

Cd is the ratio of the current area of air intake (a-b) to the effective area and g is the acceleration of gravity.

Two [° C] is the ideal temperature for, for example, animals located in the building room.

In this way, it becomes possible to achieve that the control and regulation of air flow is continuously and automatically adapted to the changed conditions that are for the stable building and the weather, and therefore can be kept optimally for the benefit of both animal welfare and the economy.

The invention also relates, as mentioned, to the use of the method for animal sheds.

This ensures that the air intake can be optimized in the stables for the benefit of both animal welfare and the operating economy.

The invention will now be explained in more detail with reference to the drawings, in which:

FIG. Figure 1 shows a principle sketch of a building with valves for air intake and active air outlet.

FIG. 2 shows an example of a valve for air intake.

FIG. 3 shows an example of a flow pattern in a stable air when the so-called corrected Archimedes number is preferably less than 30.

FIG. 4 shows an example of a flow pattern in a stable air when the so-called corrected Archimedes number is preferably greater than 70.

FIG. 5 shows an example of a flow pattern in a stable air when the so-called corrected Archimedes number is preferably in the range between 30 and 70.

In FIG. 1, 1 is shown a building such as a stable building, which is provided with valves 5 for air inlet, which via regulating dampers 7 can regulate the air flow 6 to the stable building from the surroundings.

The air is discharged from the building 1 via the air outlet 2, which is active, with a fan 4 sucking the air out of the building, as shown by arrow 3.

In FIG. 2 is an example of an air intake valve 5 which can gradually open or close the air flow through the valve 5 via one or more adjustable dampers 7.

The invention comprises continuous control of the flow of air in the barn 1 based on knowledge of the dimensions of the barn 1, the number, position and dimension of the air intake valves 5 and a number of measurements.

For example, controlling the air flow 6 in the barn 1 includes controlling the flow pattern, controlling the mixing of the inflow air with the air in the barn, and controlling the air velocity in the animals' living area. For example, control of flow pattern, mixing of the inflow air with the air in the barn and the air velocity in the animals' living area is done without measuring these air flows. This is based on the establishment of a mathematical model that determines the air flow in the stable on the basis of other measurements that are more practicable.

An example of a mathematical model is the use of the corrected Archimedes number (Arc) to determine the air flow pattern in the barn.

The corrected Archimedes number is defined as follows: * _ g Cd ab WH (W + H) iTs-Ta) ^ 1 c ~~ ............. <; 2 (2-27: m:> ·, ·. ..............

Where W [m] is the length of the room, H [m] is the height of the room, a [m] is the vertical extent of the air intake, b [m] is the horizontal extent of the air intake, q [m3 / s] is the volume flow through the air intake, Ts [° C ] is the temperature of the air in the barn, Ta [° C] is the temperature of the air outside the barn, Cd is the ratio of the actual area (ab) of the air intake and the effective area and g is the acceleration of gravity.

If the corrected Archimedes number is small, for example between 20 and 40, preferably less than 30, the air 6A, as shown in FIG. 3, from the valve 5 to the air intake move up along the ceiling of the room - to the center of the room - and then circulate towards the floor where the animals are staying. During this movement, the fresh air from the intake is mixed with the air in the barn 1. This flow pattern is desired when the temperature outside the barn is lower than the temperature required by the animals. The cold outdoor air is mixed with the warm stable air before moving into the animals' living area. In this way, the animals are not exposed to traits.

In FIG. 4 shows how the air 6B in the building 1 will run when the corrected Archimedes number is large, for example between 60 and 80, preferably greater than 70. The air 6B will move from the air intake valve 5 to the floor where the animals are staying, and then - at the center of the room - circulate towards the ceiling. This flow pattern is desired when the temperature outside the barn 1 is approximately the same or higher than the temperature required by the animals. A cooling effect is achieved as the outdoor air directly affects the animals.

In FIG. 5, it is shown how air 6C will proceed in building 1 if the corrected Archimedes number is in the range between preferably 30 and 70. In this state the flow pattern is unpredictable. Climate control must quickly bring the air flow out of this state.

The invention contains that the air flow 6, 6A, 6B in the individual air intake valves 5 is measured. It is measured either in one, in some or in all the air intake valves. You can choose not to measure in all valves if you assume that all valves are adjusted correctly and moved at the same time, so that measurements in individual valves are representative of the other valves. The total air flow in the air inlet can by this assumption be found by multiplying the measurement in the individual valves 5 to air inlet.

In a preferred embodiment, a temperature sensitive electrical resistance is placed in the air intake valve 5 so that the receiver is passed by the air flow through the valve 5. The resistance is heated by passing a known current through it. The overflowing air cools the resistance - the higher the air velocity and the lower the air temperature - the more cooling. By measuring the resistance and the air temperature simultaneously, the air velocity can be found. The air temperature is measured either at a corresponding temperature sensitive resistance or by repeating the resistance measurement without heating. It is possible to convert from air velocity to air flow because the duct (valve design) is known.

When the air flow in the stable 1 is continuously controlled during operation by correcting the air intake valves 5 based on the measured outside and inside temperatures, the desired flow is maintained under temperature conditions which differ from the conditions during the regulation of the housing 1. The control of the air flow becomes more robust. and conditions for the animals will be better in all conditions.

If a good knowledge of the housing's dimensions and the actual immediate performance of the air outlets, as well as a reliable adjustment of the air inlets, is assumed, the manual adjustment of the air inlets at various air changes in the barn can be replaced by a calculated adjustment. This adjustment is made automatically by the control when commissioning the housing 1 based on data on the physical dimensions of the housing 1 and the principle of the activation of the air intake valves 5.

In addition, if the air flow is measured through the air inlet valves 5, the desired air flow can be maintained in the housing 1, even if the wind effect of the housing 1 is changed. For example, one can correct the asymmetry of the air flow in the barn 1 when the wind creates a higher pressure on the wind side and a lower pressure on the reading side. By reducing the opening rate of the air intake on the wind side and increasing the opening rate on the reading side, the air inflow through the inlets can be balanced and the symmetrical flow pattern in the stable 1 is maintained.

It is also possible to compensate if there is an imbalance between the air inlets due to inaccurate adjustment or wear in the actuating mechanism of the valves.

By combining the model-based control and measurement of the air flow in the air inlets, the adjustment of the air flow by commissioning the housing 1 becomes unnecessary.

The air flow is controlled as desired regardless of wind and temperature conditions.

Therefore, for example, there is no need for a qualified service technician to make an adjustment before commissioning a stable.

Claims (2)

1. A method for controlling and regulating the air flow (6) in buildings such as housing systems (1) provided with one or more valves (5) with adjustable opening area and an integrated volume flow measuring probe for air intake as well as one or more active air outlets (2), characterized in that the control and the regulation of the air flow (6) is effected by regulating the valves (5) for air intake, based on the use of an algorithm of the mold: where the valves (5) are controlled so that Arc <Armjn for TacTo, where 20 <Armjn <40, where preferably Armin = 30 or so Arc> Armax for Ta> To, where 60 <Armax <80, where preferably Armax = 73 where : Arc is a corrected Archimedes number, W [m] is the length of the building space, H [m] is the height of the building space, a [m] is the vertical extent of the air intake, b [m] is the horizontal extent of the air intake, q [m3 / s] is the volume flow through the air intake, Ts [° C] is the temperature of the air in the building space, Ta [° C] is the temperature of the air outside the building space, Cd is the ratio of the actual area (ab) of the air intake to the effective area and g is the acceleration of gravity. Two [° C] is the ideal temperature for, for example, animals located in the building room. Use of the method according to claim 1 for animal sheds.