Air flow regulation is part of the process of setting up ventilation and air conditioning systems, it is carried out using special control valves. air valves. Regulation of air flow in ventilation systems allows you to provide the required inflow fresh air to each of the serviced premises, and in air conditioning systems - cooling of the premises in accordance with their heat load.
To control the air flow, air valves, iris valves, systems for maintaining a constant air flow (CAV, Constant Air Volume), as well as systems for maintaining a variable air flow (VAV, Variable Air Volume) are used. Let's take a look at these solutions.
Two ways to change the air flow in the duct
In principle, there are only two ways to change the air flow in the duct - change the fan performance or bring the fan to the maximum mode and create additional resistance to the air flow in the network.
The first option requires the connection of fans through frequency converters or step transformers. In this case, the air flow will change immediately in the entire system. Adjust the air supply to one specific room in this way is not possible.
The second option is used to control the air flow in directions - by floors and by rooms. To do this, various adjustment devices are built into the corresponding air ducts, which will be discussed below.
Air shut-off valves, gate valves
The most primitive way to control the air flow is to use air shut-off valves and gates. Strictly speaking, shut-off valves and dampers are not regulators and should not be used for air flow control purposes. However, formally they provide regulation at the level of "0-1": either the duct is open and the air moves, or the duct is closed and the air flow is zero.
The difference between air valves and gate valves lies in their design. The valve, as a rule, is a body, inside of which a rotary damper is provided. If the damper is turned across the axis of the duct, it is blocked; if along the axis of the duct - it is open. At the gate, the damper moves progressively, like a closet door. Blocking the section of the duct, it reduces the air flow to zero, and, opening the section, provides air flow.
In valves and dampers, it is possible to install the damper in intermediate positions, which formally allows you to change the air flow. However, this method is the most inefficient, difficult to control and the most noisy. Indeed, it is almost impossible to catch the desired position of the damper when it is scrolling, and since the design of the dampers does not provide for the function of regulating the air flow, the dampers and dampers are quite noisy in intermediate positions.
Iris valves
Iris dampers are one of the most common solutions for air flow control in rooms. They are round valves with petals arranged along the outer diameter. When adjusted, the petals are displaced towards the axis of the valve, blocking part of the section. This creates an aerodynamically well-circumscribed surface, which helps to reduce the noise level during air flow control.
Iris valves are equipped with a scale with risks, which can be used to monitor the degree of overlap of the valve's open area. Next, the pressure drop across the valve is measured using a differential pressure gauge. The pressure drop determines the actual air flow through the valve.
Constant flow regulators
The next stage in the development of air flow control technologies is the emergence of constant flow controllers. The reason for their appearance is simple. Natural changes in the ventilation network, clogging of the filter, clogging of the external grille, replacement of the fan and other factors lead to a change in air pressure in front of the valve. But the valve was set to some standard pressure drop. How will it work in the new conditions?
If the pressure in front of the valve has decreased, the old valve settings will “transfer” the network, and the air flow into the room will decrease. If the pressure in front of the valve has increased, the old valve settings will “underpressure” the network, and the air flow into the room will increase.
However main task control system is precisely the preservation of the design air flow in all rooms throughout the entire life cycle climate system. This is where solutions for maintaining a constant air flow come to the fore.
The principle of their operation is reduced to an automatic change in the flow area of the valve, depending on external conditions. To do this, the valves are provided with a special membrane, which deforms depending on the pressure at the inlet to the valve and closes the cross section when the pressure increases or releases the cross section when the pressure decreases.
Other constant flow valves use a spring instead of a diaphragm. Increasing pressure upstream of the valve compresses the spring. The compressed spring acts on the flow area regulation mechanism, and the flow area decreases. In this case, the resistance of the valve increases, neutralizing high blood pressure to the valve. If, however, the pressure in front of the valve has decreased (for example, due to clogging of the filter), the spring is unclenched, and the orifice control mechanism increases the orifice.
The considered controllers of constant air flow operate on the basis of natural physical principles without the participation of electronics. There are also electronic systems for maintaining a constant air flow. They measure the actual pressure drop or air velocity and change the valve's orifice area accordingly.
Variable Airflow Systems
Variable air volume systems allow the supply air volume to be varied depending on the actual situation in the room, for example, depending on the number of people, concentration carbon dioxide, air temperature and other parameters.
Regulators of this type are motorized valves, the operation of which is determined by the controller, which receives information from sensors located in the room. The regulation of air flow in ventilation and air conditioning systems is carried out according to different sensors.
For ventilation, it is important to provide the required amount of fresh air in the room. At the same time, carbon dioxide concentration sensors are activated. The task of the air conditioning system is to maintain the set temperature in the room, therefore, temperature sensors are used.
In both systems, motion sensors or sensors for determining the number of people in the room can also be used. But the meaning of their installation should be discussed separately.
Certainly than more people indoors, the more fresh air should be supplied to it. But still, the primary task of the ventilation system is not to ensure the flow of air "by people", but to create a comfortable environment, which in turn is determined by the concentration of carbon dioxide. With a high concentration of carbon dioxide, ventilation must operate in a more powerful mode, even if there is only one person in the room. Similarly, the main sign of the operation of the air conditioning system is the temperature of the air, and not the number of people.
However, occupancy sensors make it possible to determine whether a given room needs to be serviced at all. this moment. In addition, the automation system can "understand" that "it's time for the night", and it is unlikely that anyone will work in the office in question, which means that it makes no sense to spend resources on its air conditioning. Thus, in systems with variable air flow, different sensors can perform different functions - to form a regulatory influence and to understand the need for the operation of the system as such.
The most advanced systems with variable air flow allow, based on several controllers, to generate a signal to control the fan. For example, in one period of time, almost all regulators are open, the fan operates in the mode high performance. At another point in time, some of the regulators lowered the air flow. The fan can operate in a more economical mode. At the third moment of time, people changed their location, moving from one room to another. Regulators worked out the situation, but total consumption air has almost not changed, therefore, the fan will continue to operate in the same economy mode. Finally, it is possible that almost all regulators are closed. In this case, the fan reduces speed to a minimum or turns off.
This approach allows you to avoid constant manual reconfiguration of the ventilation system, significantly increase its energy efficiency, increase the service life of equipment, accumulate statistics on the climatic regime of the building and its changes throughout the year and during the day, depending on various factors - the number of people, outdoor temperature, weather phenomena.
Yury Khomutsky, technical editor of the journal "Climate World">
IRIS VALVE WITH SERVO
Thanks to the unique butterfly valve design, the air flow can be measured and controlled within one unit and one process, delivering a balanced amount of air into the room. The result is a permanently comfortable microclimate.
IRIS butterfly valves allow you to quickly and accurately adjust the air flow. They cope wherever individual comfort control and precise air control are needed.
Flow measurement and regulation to ensure maximum comfort
Balancing the air flow is usually a labor intensive and expensive operation when starting a ventilation system. The linear air flow limitation characteristic of lens butterfly valves makes this operation easier.
Throttle valve design
IRIS throttle dampers can function in both supply and exhaust installations, eliminating the risk associated with incorrect installation errors. IRIS lens throttle dampers consist of a galvanized steel body, lens planes that regulate the air flow, a lever for smoothly changing the diameter of the hole. In addition, they are equipped with two tips for connecting a device that measures the strength of the air flow.
Throttle valves are equipped with EPDM rubber seals for a tight connection with the ventilation ducts.
Thanks to the motor mount, it is possible automatic control stream without having to manually change the settings. A special plane is provided for stable mounting of the servo motor, protecting it from movement and damage.
What makes lens throttle valves different from standard throttle valves?
Conventional dampers increase the speed of air flow along the walls of the channels, while generating a lot of noise. Thanks to the IRIS lens closing of the throttle valves, suppression does not cause turbulences and noise in the channels. This allows higher flows or pressures than standard butterfly valves, without noise in the installation. This is a great simplification and savings, because. there is no need to use additional soundproofing elements. Appropriate noise attenuation is possible through the correct installation of dampers in the ventilation system.
For precise measurement and control of air flow, butterfly valves should be placed on straight sections, no closer than:
1. 4 x air duct diameter in front of the throttle valve,
2. 1 x duct diameter behind throttle.
The use of lens dampers is very important for ensuring the hygiene of the ventilation installation. Due to the possibility of full opening, cleaning robots can successfully enter the channels connected to this kind of butterfly valves.
Advantages of IRIS butterfly valves:
1. low noise level in channels
2. easy installation
3. excellent balancing of the air flow, thanks to the measuring and regulating unit
4.Easy and fast flow adjustment without the need additional devices- use of a handle or a servomotor
5. Accurate flow measurement
6. stepless adjustment - manually using a lever or automatically using the version with a servomotor
7. design allowing easy access for cleaning robots.
Variable air flow controllers KPRK for air ducts round section designed to maintain the set air flow rate in ventilation systems with variable air flow (VAV) or constant air flow (CAV). In VAV mode, the air flow setpoint can be changed using a signal from an external sensor, controller or dispatch system; in CAV mode, the regulators maintain the set air flow
The main components of flow regulators are an air valve, a special pressure receiver (probe) for measuring air flow and an electric actuator with a built-in controller and pressure sensor. The difference between the total and static pressures at the measuring probe depends on the air flow through the regulator. The current differential pressure is measured by a pressure sensor built into the actuator. The electric actuator, under the control of the built-in controller, opens or closes the air valve, maintaining the air flow through the regulator at a predetermined level.
KRPK regulators can operate in several modes depending on the connection scheme and settings. Air flow rates in m3/h are programmed at the factory. If necessary, the settings can be changed using a smartphone (with NFC support), a programmer, a computer or a supervisory system via MP-bus, Modbus, LonWorks or KNX protocol.
Regulators are available in twelve versions:
- KRPK…B1 – basic model with MP-bus and NFC support;
- KRPK…BM1 – controller with Modbus support;
- KRPK…VL1 – regulator with LonWorks support;
- KPRK…BK1 – controller with KNX support;
- KPRK-I…B1 – controller in a heat/sound insulated housing with MP-bus and NFC support;
- KPRK-I…BM1 – controller in a heat/sound insulated housing with Modbus support;
- KPRK-I…VL1 – controller in a heat/sound insulated housing with LonWorks support;
- KPRK-I…BK1 – controller in heat/sound insulated housing with KNX support;
- KPRK-Sh…B1 – controller in a heat/sound insulated housing and a silencer with MP-bus and NFC support;
- KPRK-Sh…BM1 – controller in a heat/sound insulated housing and a noise suppressor with Modbus support;
- KRPK-Sh…VL1 – regulator in a heat/sound insulated housing and a noise suppressor with LonWorks support;
- KPRK-Sh…BK1 is a controller in a heat/sound insulated housing and a noise suppressor with KNX support.
For the coordinated operation of several variable air flow controllers KPRK and ventilation unit it is recommended to use Optimizer - a regulator that provides a change in the fan speed depending on current need. Up to eight KPRK controllers can be connected to the Optimizer, and several Optimizers can be combined, if necessary, in Master-Slave mode. Variable air flow controllers remain operational and can be operated regardless of their spatial orientation, except when the measuring probe fittings are directed downwards. The direction of air flow must correspond to the arrow on the body of the product. Regulators are made of galvanized steel. Models KPRK-I and KPRK-Sh are made in a heat/sound insulated housing with an insulation thickness of 50 mm; KPRK-Sh is additionally equipped with a 650 mm silencer on the air outlet side. Body nozzles are equipped rubber seals, which ensures the tightness of the connection with the air ducts.
Systems with variable air consumption (VAV - Variable Air Volume) are energy efficient system ventilation that saves energy without sacrificing comfort. The system enables independent, for each individual room, regulation of ventilation parameters, and also saves capital and operating costs.
The modern base of equipment and automation allows you to create such systems at prices that almost do not exceed the prices conventional systems ventilation, while allowing efficient use of resources. All this is the reason for the growing popularity of the VAV system.
Let's consider what a VAV system is, how it works, what advantages it gives, using the example of a cottage ventilation system with an area of 250 sq.m. ().
Benefits of Variable Airflow Systems
Variable Air Volume (VAV) systems have been widely used in America for several decades and Western Europe, they came to the Russian market quite recently. Users in Western countries have highly appreciated the advantage of independent room-by-room control of ventilation parameters, as well as the possibility of saving capital and operating costs.
Ventilation "Variable Air Volume" systems operate in the mode of changing the amount of air supplied. Changes in the heat load of the premises are compensated by changing the volumes of supply and extract air at its constant temperature coming from the central supply unit.
The VAV ventilation system responds to changes in heat load individual rooms or areas of a building and changes the actual amount of air supplied to a room or area.
Due to this, ventilation works at general meaning air flow rate less than necessary for the total maximum heat load of all individual rooms.
This reduces energy consumption while maintaining the desired indoor air quality. The reduction in energy costs can be from 25-50% compared to ventilation systems with a constant air flow.
Consider the efficiency on the example of ventilation country house
250 m², with three bedrooms
With traditional ventilation system, for a dwelling of this size, an air flow of about 1000 m³ / h is required, and in winter for heating supply air before comfortable temperature about 15 kWh is required. At the same time, a significant part of the energy will be wasted, because people for whom ventilation works cannot be in the whole cottage at once: they spend the night in the bedrooms, and the day in other rooms. However, selectively reduce performance traditional system ventilation in several rooms is not possible, since the balancing of the air valves, which can be used to control the air supply to the rooms, is carried out at the commissioning stage, and the flow ratio cannot be changed during operation. The user can only reduce the total air flow, but then it will become stuffy in the rooms where people are.
If you connect electric actuators to the air valves, which will allow you to remotely control the position of the damper flap and thereby regulate the air flow through it, then it will be possible to turn on and off ventilation separately in each room using conventional switches. The problem is that it is very difficult to manage such a system, because simultaneously with the closing of some of the valves, it will be necessary to reduce the performance of the ventilation system by strictly a certain amount so that the air flow in the rest of the rooms remains unchanged and as a result the improvement will turn into a headache.
Using a VAV system allows you to make all these adjustments in automatic mode. And so we install the simplest VAV system, which allows you to separately turn on and off the air supply to the bedrooms and other rooms. In night mode, air is supplied only to the bedrooms, so the air flow is about 375 m³/h (based on 125 m³/h for each bedroom, area 20 m²), and the energy consumption is about 5 kWh, i.e. 3 times less than in the first version.
Having received the possibility of separate control, in different rooms it is possible to supplement the system with the latest automation of climate control, so the use of valves with proportional electric drives will make the control smooth and even more convenient; and if we connect the on/off of the air supply by the signal of the presence sensor, we get an analogue of the Smart Eye system used in domestic split systems but on a whole new level. For further automatization, sensors of temperature, humidity, CO2 concentration, etc. can be integrated into the system, which in the end will not only save energy, but also significantly increase the level of comfort.
If all the automation units that control the electric actuators of the air valves are connected by a single control bus, then it will be possible to centrally control the entire system in scenarios. So, you can create and set individual operating modes for different rooms, in different life situations, So:
at night- air is supplied only to the bedrooms, and in other rooms the valves are open at a minimum level; afternoon- air is supplied to rooms, kitchens, and other premises, except for bedrooms. In the bedrooms, the valves are closed or open at a minimum level.
whole family to gather- increase the air flow in the living room; nobody in the house- cyclic ventilation is configured, which will not allow odors and dampness to occur, but will save resources.
For independent control of not only the volume, but also the temperature of the supply air in each of the rooms, you can install additional heaters (low-power heaters) controlled by individual power controllers. This will allow air to be supplied from the ventilation unit with a minimum allowable temperature(+18°C), individually heating it to the required level in each room. Such technical solution will further reduce energy consumption, and bring us closer to the "Smart Home" system.
The scheme of operation of such a system is rather a question of a specialized specialist, so here we will give only one, the most a simple circuit(working and erroneous options) with an explanation of how it works. But apart from simple systems, there are more complex options allowing you to create any VAV systems - from household budget systems with two valves to multifunctional ventilation systems administrative buildings with floor air flow control.
Call, the specialists of the company "OVK Engineering" will consult, help you choose best option, design and install a VAV system that is ideal for you.
Why VAV systems should be installed by professionals
The easiest way to answer this question is with an example. Consider a typical configuration of a variable air flow system and the mistakes that can be made in its design. The illustration shows an example of the correct configuration of the air duct network of a VAV system:
1. Correct scheme of VAV system with variable air flow
In the upper part there is a controlled valve that serves three rooms (three bedrooms from our example) => These rooms have throttle valves with manual control for balancing at the stage of commissioning. The resistance of these valves will not change* during operation, so they do not affect the accuracy of maintaining the air flow.
A valve with manual control is connected to the main air duct, which has a constant air flow P=const. Such a valve may be needed to provide normal operation ventilation unit when all other valves are closed. => The air duct with this damper is led into the room with a constant air supply.
The scheme is simple, working and efficient.
Now let's look at the mistakes that can be made when designing the air duct network of a VAV system:
2. Scheme of a VAV system with an error 
Incorrect duct branches are highlighted in red. Valves #2 and #3 are connected to a duct running from the junction point to VAV valve #1. When the damper position of valve #1 is changed, the pressure in the air duct near valves #2 and 3 will change, so the air flow through them will not be constant. Piloted valve #4 must not be connected to the main duct, because changing the air flow through it will cause the pressure P2 (at the branch point) to be not constant. And valve #5 cannot be connected as shown in the diagram, for the same reason as valves #2 and 3.
*Of course, you can set up controlled airflow for each bedroom, but in this case there will be more complex scheme, which we do not consider in this article.
