Supply and exhaust ventilation: principle of operation and features of arrangement
In a room filled with fresh air, it is easier to breathe, more productive to work and sleep better. But opening a window every 2-3 hours for ventilation is problematic, do you agree? Especially at night, when all family members are sweet asleep.
One of the automated solutions for this problem is the supply and exhaust ventilation (PVV) of the room. But how to make it right? We will help you to learn the principle of operation and understand the peculiarities of arrangement.
In our article the components of the supply and exhaust system, the rules for their calculation and standards for air exchange in rooms of different types are considered.
Selected diagrams arrangement of ventilation, a photo of the individual elements of the system, provides a useful video recommendation on the device vent system in a private home with their own hands.
Classification and types of ventilation systems
The creation of ventilation in the cottage is conditioned by the fact that there must be a continuous exchange of air masses. Old, used air with a lot of carbon dioxide must be removed from the premises, replacing it with new air constantly containing oxygen. from the street.
If you stop this air exchange, the microclimate inside will quickly become far from favorable for human health.
According to the norms for living rooms, the optimum atmosphere is a temperature around 20-25 degrees and a relative humidity of 30-60%, depending on the time of year and the reading on the thermometer outside the window
To maintain the established GOST parameters air exchange, the ventilation system in the house, made his own hands or outsourced installers, must continuously change the air in the rooms.
For example, for living rooms in a cottage the air exchange rate per hour is set to “1”. That is, an hour in them should be completely replaced by the entire volume of air.
The purpose of ventilation is to control the following factors:
Everyone in the house breathes out carbon dioxide around the clock. Also in a residential structure there are fireplaces, gas and electric stoves, numerous household appliances, that is, the sources of heat, moisture, dust and gases in the cottage a lot of. And all this must be removed from the premises for the microclimate to be suitable for habitation.
According to the method of air movement, ventilation systems are divided:
The first option involves the movement of air masses due to the existence of a pressure difference between outside and inside the ventilated building. It can be organized. with the use of adjustable dampers, and disorganized. only through windows, doors and vents in the foundation.
In the second case, air is forced to move through rooms and ventilation ducts using mechanical devices. This variant is energy-dependent, but more effective.
The main disadvantage of the mechanical ventilation system is its dependence on electricity supply. Without electricity, the fans stop rotating, and the efficiency of air exchange is immediately reduced
According to the purpose of ventilation systems are divided into:
The former works to supply air to the dwelling from the outside, while the latter works to exhaust from the structure. The third option. supply and exhaust designs are a symbiosis of the first two. Features of calculation of supply and exhaust system we discussed in detail in this article.
Principle of operation of different types of devices
The main criterion for selecting a fan. its structure and principle of functioning. Design features and technical nuances determine the efficiency of the device, noise level, economy of operation and the possibility of its use in certain conditions.
Most household fans belong to the group of axial devices. Their blades, connected with the working part, rotate around the central axis
The group of axial fans includes independently positioned devices and devices installed in ducts
In centrifugal fans, the impeller rotates inside the housing, driven by a motor located outside the system. Centrifugal devices mainly serve industrial and commercial facilities
Domestic appliances include bladeless versions. According to the principle of operation, they are centrifugal, which by design can be with or without blades
Axial fan. the classic fan
Axial (axial) fan is widely used in household ventilation systems in private homes, in the exhausts of sanitary conveniences, in complex exhaust systems, as a cooling element in various equipment and electronics, as well as in wind tunnels and turbofan engines in the aviation industry.
The design of the models is characterized by simplicity and small size. The main elements: the cylindrical body, the impeller with blades and the drive. Internal diameter of the cylinder should allow unimpeded rotation of the impeller. The interval between the blades and the housing is limited to 1.5% of the length of the rotating blade.
In order to reduce hydraulic losses and improve aerodynamic characteristics, the design is supplemented by a collector, diffuser and fairing on both sides of the impeller
Operating principle: Rotating blades capture air and push it outwards along the impeller axis. There is almost no movement of air flows in radial direction. Productivity of the equipment is regulated by the rotation of blades.
Distinctive features of axial models:
- does not require a large area for installation
- economical power consumption;
- low noise level;
- easy operation and repair;
- low cost.
The advantages of axial fans operation and use have made them widely popular in everyday life. Casing models for electric appliance cooling and portable axial fan units with grilles are in widespread use.
Axial fans with a wall panel are installed to enhance air exchange in wall openings and other supporting constructions. They can operate in two modes: suction and blowing
Centrifugal model. strength and high power
Centrifugal (centrifugal) fans are highly efficient. the units are capable of generating high pressures and operating in harsh conditions. The design of the equipment includes the following elements.
Housing. The diffuser casing is made of riveted or welded sheet metal. The hollow casing has a spiral snail shape, and the design includes suction and discharge spigots. The casing is reinforced with fins or cross bars to provide rigidity.
The top of the “snail” is closed with an additional box or clad with noise-absorbing panels. This is necessary to reduce the noise level during the operation of the air handling unit
Impeller. Blade rotor consists of two discs, vanes and a hub.
The design of the wheel determines the conditions under which the ventilator is used:
- diskless. transports streams with solid components;
- single-disk. movement of air media with small solid particles;
- double-disc. circulation of clean air masses in different pressure ranges;
- Three-disk. providing two-way suction.
impeller mounting to the shaft by means of hubs. The blades are fixed to the discs and hubs.
blades. The performance and efficiency of the unit as a whole depends to a large extent on the shape of the blades:
- aerodynamic wing. ensures quietness, good performance, high temperature resistance of the appliance;
- curved back. prevent accumulation of dust inside the fan, suitable for use in environments with high oppression;
- forward curved. fans with “forward” ribs are designed for high air volume and high pressure applications and are erosion resistant;
- Radial. compact units with medium efficiency; rotor guides are treated with an erosion control compound.
In wheels with “back” blades, the difference in static and full pressure values is not large, so their level of efficiency is high. Up to 80% efficiency.
The forward curved blades generate a high exit velocity of air. The unit retains 60% of its efficiency. The advantage of “front” blades is that they obtain the required parameters with smaller dimensions of the fan
In centrifugal machines, the air moves in an axial direction and is expelled in a radial direction. Centrifugal forces push the air masses through the cylindrical body.
The whole process can be divided into several steps:
- As the wheel rotates, the air between the blades rushes to the edge of the rotor.
- In the center of the impeller, a low-pressure zone is created. This causes the air masses to be drawn in from the outside.
- In the center of the blades, the airflow changes direction from axial to radial and flows into the gap between the blades.
- Rapid spinning causes the air masses to rush against the inner wall of the casing.
- The kinetic energy is partially converted into compression energy and the air speed is reduced. a volumetric air flow is collected inside the “snail” and excess pressure is formed.
- The gaseous mass rushes to the outlet spigot, enters the pipeline, and then. to the working area.
Which fan is better to choose
Before buying a ventilating device for the house, you need to know what parameters you need to pay attention to.
So, expert advice when choosing household fans:
- Blade size. Optimal diameter is recommended 10 to 15 cm, and they must be protected by a screen with small holes.
- Power. The larger this indicator, the greater the volume can handle this device.
- Noise level. This parameter is especially necessary to pay attention to when buying cheap models.
- Functionality. Most fans have additional functions such as ionization, heating, they also have a timer, remote control, and more.
- Controls. Sensor or button navigation.
- The air space to be blown. The largest area for such cooling devices is 50 m 2.
- Angle of rotation. Many models have an angle of 45-360 degrees.
- Modes. Different speeds when the air flow is very important, because it creates a comfortable stay in the room.
- Location of the fans. In terms of location, the devices can be window, wall or ceiling-mounted.
Let’s see in detail which models are best for the bathroom and kitchen.
Kitchen fans for the hood must have a high power, which can not only refresh the air in the kitchen, but also to withstand high temperatures. Such a suitable device is the Wolter KA KATD 225-4 Stb.
At the same time, the appliance for the kitchen hood has the following parameters:
And also for the kitchen fans is characterized by the fact that they can withstand temperatures of moving air up to 95 degrees.
The ideal option when selecting an exhaust unit for the bathroom will be a device with an installed humidity sensor. In this case, the most popular is the model SILENT-100 CHZ from “Soler Palau”.
It is most positively evaluated by domestic users for what it has:
- low noise level in operation (up to 24.5 dB);
- long service life;
- Has a large capacity(95 m3/hour);
- built-in timer;
- Relatively low power consumption (80 W).
But for a bathroom with a large area over 5 m 2 must be sufficient exhaust air, so you need to choose a more productive fan. Such is the device EAF-150 from “Electrolux”.
It is distinguished by the following characteristics:
Select the desired mode in it can be achieved by resetting the jumper placed inside the timer box.
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Extractor for the kitchen and bathroom will have advantages if all the parameters are chosen correctly. And then this multifunctional device will create a comfortable and pleasant microclimate in the room.
Purpose and types of ventilation
Modern ventilation systems can be of different types and, depending on their purpose, are divided into several subgroups. This division is made on several parameters: the direction of air movement, the method of setting air masses in motion, served territory.
What is the ventilation in the premises in the direction of air movement? According to this parameter systems are divided into two large groups:
There is also ventilation and its classification by the factor that sets the air in motion. According to this parameter they are divided into:
There is also a division of ventilation and types of which are different, depending on the area served. According to this principle, ventilation systems are divided into:
All considered types of ventilation systems can be used both separately and together in one building or even room.
Systems can also be classified into ducted and ductless, depending on whether they use ductwork or air moves through holes in the walls or fans without connected pipes.
Let’s discuss in detail all types and subtypes of ventilation systems, how they differ and what their goals are.
As already mentioned, natural ventilation is one of the popular varieties of modern systems. This type of room ventilation implies that the air is set in motion by natural factors. precisely, it is the difference in pressure between the internal volume and the outside atmosphere. For it to function, the pressure outside should be a little less than inside the room. If this factor occurs, it starts air movement through specially designed ventilation ducts.
A striking example of such ventilation is the device of exhaust ducts in the walls of multi-storey and private houses. The main positive factor in the use of natural ventilation is cheapness. It is not necessary to use expensive equipment and arrange the connection to electricity. Air exchange occurs by itself. But it should be borne in mind that there are also negative aspects of such a system. First of all it depends on atmospheric parameters.
Air movement in natural ducts occurs only when there is a negative pressure difference, but this is not always the case. There are times when the pressure inside and outside the room is equalized. Then the air exchange stops or even vice versa, there is a reverse draught. The natural system reacts very strongly to precipitation and weather changes. If in frosty, sunny weather the draught can be several times greater than the calculated one, in autumn on a rainy day there can also be a movement of outside air into the room.
Considering further the types of ventilation systems by method of bringing air into motion, let us focus on the forced network. In it, unlike the natural one, electric power is used for air movement. The air exchange is forced by ventilation units: fans, air inlet and outlet units.
The main driving element of such a system is a fan. This is a device that consists of a housing and an impeller of various types and an electric motor. An electric motor drives an impeller, which is designed to capture air flows and move them from the fan’s intake to the exhaust.
Fans are generally classified into two broad types:
In axial fans, the air moves through the impeller perpendicular to the vanes. In centrifugal fans, the air moves parallel to the blade, as if it is circumvented.
In addition to the fan, the forced air system can consist of additional elements. First of all, it concerns the duct systems, as in them the air moves through a network of connected ducts (rigid and flexible), there is a need to use gate valves, air flow regulators, and other elements:
- Filters for cleaning the supply or exhaust air of dust and pollutants;
- sound attenuators to reduce vibration and noise levels;
- Heaters: water or electric units for heating the supply air;
- Grilles, diffusers, anemostats, and other flow distribution devices.
A large number of auxiliary and mounting materials are also used. Including insulators, clamps, and temperature and fan power regulators.
Air supply systems
As the name implies, these types of ventilation systems, such as supply air, are designed to bring outside air into the room. They can be both natural and mechanical. Mechanical systems are the most common because they allow for precise control of supplied air volume and its characteristics.
Natural air inlets are less commonly used, and are mostly used for uncontrolled air supply. That is, they have an exhaust system that operates according to the calculated parameters, and the air inflow is organized through the cracks in the windows, special holes or grilles naturally at the expense of the pressure difference.
And the supply system can operate in tandem with the exhaust, both natural and mechanical type. It should be borne in mind that the two systems work together because the volume of supply and exhaust air must be the same.
These types of ventilation systems, such as exhaust systems are designed to remove air from the room or part of it. They can be both mechanical and natural. If natural supply systems are not widespread, then their exhaust variants have long been used effectively.
In housing, the main purpose of exhaust systems is to remove human waste and other air pollutants. Firstly, it is necessary to remove carbon dioxide, which is formed when breathing. And it is formed fairly large amounts. In addition it is necessary to remove water vapor and polluted air from the bathrooms and kitchens. In industry, exhaust ventilation is largely designed to remove contaminants that occur during the manufacturing process.
Types of ventilation
Today, a couple of options created by air exchange systems, able to provide a comfortable environment indoors.
They are classified by the following indicators:
- which method they move air. natural or unnatural,
- Their purpose. supply or exhaust,
- For which areas are designed. general exchange or local,
- Constructive performance. ductless or channelized.
- The temperature difference between inside and outside the building,
- unequal pressure of the “air column” between the room (lower level) and the exhaust unit on the roof (upper level),
- Wind pressure.
Such systems are simple and do not require complex equipment and electricity consumption. It is easy to make their own hands. But, their efficiency quite often depends on variable factors, as well as, temperature of air masses, wind speed and its direction, on this basis to consider them reliable does not make sense.
It allows to move the incoming fresh air space over long distances.
Units are capable of bringing in fresh air and expelling exhaust air at right volumes, regardless of the external environment. Only it is necessary to consider that in this case, the cost of electricity for their work can be high.
They are classified according to the method of supply and removal of air, based on that they can be:
Instructions require that the choice must take into account the purpose, number and specific features of the room (presence and temperament of the source of pollution, number of people, layout).
Fresh air supply systems
Their main purpose. to supply the right amount of air into the room.
In most cases, before it goes through a certain level of training, which may include:
- cleaning from outside dust,
- Preheating during cold periods,
- Cooling during hot periods,
- Wetting to maintain the usual moisture balance.
The ventilation system can be placed in a single enclosure or dialed from individual elements, as well, it is included:
- air heaters,
- duct system,
- air flow distributors.
In one hour the capacity of units can reach dozens (mini air inlets) or a couple of tens of thousands (basic air inlets) of cubic meters of fresh air.
Tip: Through the heating element you can provide winter heating to a temperature in the range of 18-29 ° C, and then supply it to the room.
- Air intake grilles through which ambient air enters the ventilation system. In addition to its decorative function, it protects the system from foreign objects and precipitation in the form of rain and snow.
- An air vent is needed to prevent outside air from getting into the rooms when the ventilation system is shut off. This device is especially helpful in the winter period.
- Filter is a barrier for down, dust and insects. The system can be of two types. unrefined and narrow.
Tip: Filter must be cleaned of accumulated dirt once every thirty days.
- The air heater heats the outdoor air masses coming from the street in winter. Use an electric or water circuit.
- Muffler protects the occupants from the constant aerodynamic noise traveling along the ducts during operation of equipment.
- The fan blows fresh air into the room and generates the pressure of the air masses.
- Air ducts are used for distributing air masses into the rooms. Tees, bends and adapters are used. They can be rectangular or circular in cross-section, and flexible or solid. Metal or plastic are used for their manufacture.
- Air distributors are needed to bring the airflow into the room. In most cases these are different types and shapes of grilles or diffusers. In addition to decorative functions, they evenly disperse the air flow around the room, are used for its personal adjustment.
- Automation. helps to regulate and control the ventilation system.
For air exchange of apartments and houses actively use small ventilation systems consisting of a network of ducts with a supply unit. It is controlled by a remote control that allows you to adjust the air supply and heating. Besides, there are devices equipped with timers that turn on the installation at a certain time.
Often have the option of connecting an outside exhaust fan to the system. Thanks to the ventilation system automation, the simultaneous work of the air handling unit and the exhaust unit is ensured. After installation and wiring is completed, an acceptance report is drawn up for the supply and exhaust ventilation systems, guaranteeing their correct operation.
In most cases, the devices are protected against overheating by thermal protection built into the winding of the fan motor. Heaters are equipped with thermostats, which also protect from overheating and fire.
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Adequate supply systems may be equipped with a differential manometer used to control the dynamic pressure drop in the incoming air flow. In the event of a shutdown, the cold air inlet in the apartment is automatically cut off.
Equipment for air intake
To ensure the air supply in the apartment there are two types of installations: universal and compact.
Universal air inlets are mounted under the ceiling or on the balcony. They are designed to serve the entire apartment, so you must install a duct system. Installation of such units is quite complicated, so it is better to invite professionals.
The compact supply equipment is installed on a wall or on a door. Air ducts are not needed in this case, as the filtered and heated air is fed into the room through the hole in the wall or door. The air flow rate can be set manually just like any other parameter.
Exhaust ventilation is the lungs of the apartment or house. The quality of life depends on their operation. Together with the experts, let’s look at the main issues involved in installing and operating this system
Choosing a fan for the bathroom and toilet
In the bathroom there is almost always an excess of moisture, which must be taken into account when selecting a fan. First of all, the air in the bathroom is more dense, and this requires increased power of the extractor. You also need a humidity sensor, good insulation and protection against splashing water. Will be useful and timer delay off, which will allow the fan to work up to 20 minutes after visiting the bathroom. There are timers that start the fan when the humidity level reaches a certain point.
For the bathroom you can choose more simple fans, because here the main problem is to remove germs and unpleasant odors. A fan that is too powerful is not necessary, as it will excessively cool a small room. Suitable fume extraction device that turns on with the ignition of the light. A good solution is to use a fan with a delay timer, which allows for 20-25 minutes to remove unpleasant odors in the toilet and automatically turns off.
For the bathroom you can choose more simple fans, because here the main problem is to remove germs and unpleasant odors.
Conclusion and useful video
Roller #1. Useful information on the principles of the ventilation system:
Roller #2. The exhaust air also takes the heat out of the house. Here is a visual demonstration of heat loss calculations associated with the work of the ventilation system:
Proper calculation of ventilation. the basis of its successful functioning and the pledge of a favorable microclimate in the house or apartment. Knowledge of the basic parameters on which such calculations are based, will allow not only to design correctly ventilation system during construction, but also to correct its condition if circumstances change.