The presence of a ventilation system is necessary to ensure air exchange inside the building by removing excess moisture, heat, and harmful substances. Its presence is one of the main conditions for ensuring life.

If there are no types of ventilation systems in the room, this harms the human body and leads to the formation of fungi, because... in conditions of lack of air exchange, condensation forms.

We suggest you understand the existing types of ventilation systems and the principles of their operation.

Systems are classified according to different criteria:

  • method of submission;
  • purpose;
  • air exchange method;
  • design.

The type of ventilation is determined at the design stage of the building. In this case, both the economic and technical aspects, as well as sanitary and hygienic conditions, are taken into account.

Types of ventilation system according to supply method

Based on the methods of supplying and removing air from the room, 3 categories of ventilation can be distinguished:

  • natural;
  • mechanical;
  • mixed.

Conclusions and useful video on the topic

This video is a kind of educational program about ventilation. Here the very concept of ventilation is discussed in detail and all issues related to its competent design are covered:

Master class on installing a ventilation system:

Both business managers and private developers must understand that the normal functioning of those for whom they are responsible depends on the effectiveness of ventilation. Sometimes people's lives are also in question. You cannot miss this moment and save on it.

Mechanical ventilation can be general and local (local).

Mechanical general ventilation can be ductless or ducted. The most common is duct ventilation. With it, the air change is forced - carried out by mechanical draft with axial or centrifugal fans or ejector units (Fig. 6), moving air through special channels (air ducts). With mechanical general ventilation (Fig. 7), the premises are equipped with supply, exhaust and supply and exhaust systems.

Fans are used in supply, exhaust and supply and exhaust systems, and ejector units are used mainly in exhaust systems to remove explosive vapors and gases from industrial premises, where the installation of conventional type fans (sparking, non-explosion-proof) is not allowed and there is no way to retain explosive contaminants.

Rice. 6. Diagram of mechanical stimulators of air movement in ventilation units:
a - centrifugal fan: 1 - housing; 2 - blade wheel; 3 - inlet; 4 - outlet; b - axial fan: 1 - housing; 2 - inlet; 3 - blade wheel; 4 - diffuser; 5 - outlet; c - ejector installation: 1 - air injection channel; 2 - nozzle; 3 - air leaving the nozzle; 4 - exhaust air duct; g - axial roof fan; d - centrifugal roof fan; 1 - electric motor; 2 - impeller; 3 - hatch; 4 - self-opening valve; 5 - casing; 6 - umbrella; 7 - hinged hood

With a general supply mechanical ventilation system, an air intake (shaft) is installed outside the building to take in clean air. The air intake structure is located in places where there is no contamination. The air is taken at a height of at least 2.5 m from the ground. With this ventilation, air is sucked in by a fan, passes through a heater, where it is heated, humidified and, in some cases, dried. After this, the air is supplied to the room through a system of air ducts with holes or through branches with special nozzles for directing the supply air (Fig. 7, a). To regulate the amount of air supplied, valves, dampers or gates are installed in the branches. With such a ventilation system, due to a slight increase in pressure, contaminated air is forced out of the premises through leaks in structures, doors, windows, lanterns, cracks and pores in walls. This creates some danger of toxic vapors and gases entering adjacent rooms, and in case of fires, fire, which must be taken into account when designing and operating such ventilation systems.


Rice. 7. General mechanical ventilation schemes:
a - supply ventilation: 1 - air intake shaft; 2 - heater; 3 - air humidifier or dehumidifier; 4 - fan; 5 - suction air duct; 6 - bypass branch of the suction air duct; 7 - supply main air duct; c - branches of the discharge air duct; 9 - nozzles for directing supply air; b - pressure distribution in the ventilation unit; c - exhaust ventilation: 1 - receiving air ducts with nozzles; 2 - main exhaust air duct; 3 - fan; 4 - cleaner; 5 - exhaust channel; d - supply and exhaust ventilation: 1 - air intake shaft; 2 - fan; 3 - air heater and humidifier; 4 - supply main air duct; 5 - branches of the discharge main air duct; 6 - branches of the exhaust main air duct; 7 - main exhaust air duct; 8 - exhaust system fan; 9 - air cleaner; d - supply and exhaust ventilation with recirculation: 1 - air intake shaft; 2 - valves (dampers); 3 - supply system fan; 4 - supply main air duct; 5 - supply air ducts (branches); 6 - air cleaner; 7 - exhaust air ducts (branches); 8 - main exhaust air duct; 9 - exhaust system fan; 10 - air cleaner

It is recommended to supply air to the work area in the space from the floor level to the breathing level - 1.8-2 m and at possibly low speeds - 0.3 m/s. Do not supply air through areas in which the air is more polluted than in the ventilated room.

With a general exhaust mechanical ventilation system, contaminated or overheated air is removed through a network of air ducts using a fan (Fig. 7c). Clean air is sucked in naturally through leaks in the structures of doors, windows, as well as the pores of walls and partitions. It is not allowed to combine into one common exhaust system contaminants (suction) of easily condensable vapors, gases and substances that, when mixed in the main air, can create a toxic, flammable or explosive mechanical mixture or chemical compounds. For example, it is not allowed to combine suction from pneumatic conveying installations with suction from painting and drying chambers, from painting booths or chambers, when nitrocellulose varnishes are used in one of the booths (or chambers), and polyester varnishes in the other.

Supply and exhaust general exchange mechanical ventilation can be open or closed. The open-loop system consists of two separate systems - supply and exhaust (Fig. 7,d). One system supplies clean air to the room, while the second simultaneously removes polluted air.

The supply openings are often placed in the upper zone of the room, and the exhaust openings of the air ducts are at different heights depending on the purpose of the room and the density of the contaminants being removed.

The supply and exhaust system in interconnected rooms is arranged in such a way as to exclude the possibility of air flowing from rooms with a large emission of harmful substances or with the presence of toxic, explosive gases, vapors or dust into rooms where there is less of these contaminants or none at all.

The purpose of supply ventilation systems is to replace the air removed by general exhaust ventilation, local suction and spent on technological needs (combustion, compressor units, pneumatic transport, etc.).

A supply and exhaust closed ventilation system or ventilation with recirculation (Fig. 7, e) is a closed supply and exhaust ventilation in which the air sucked by the exhaust system is re-supplied into the room by the supply ventilation partially with the supply of fresh air. Ventilation with recirculation may only be installed in rooms where there are no toxic fire or explosive contaminants.

Building ventilation is special construction solutions, a set of utilities and equipment that maintain specified air environment parameters at various facilities (apartments, houses, public, industrial, utility rooms).

Ventilation systems create controlled or unregulated air exchange. Ventilation units maintain the necessary technological or hygienic characteristics of air (temperature, composition, humidity). A particularly significant parameter is the speed of the air flow. In comfortable conditions, a person should not feel the movement of air masses.

Ventilation systems are designed and coordinated with heating and power supply projects, as well as with the relevant authorities before the start of construction work. At the same time, the optimal type of ventilation for a given facility is selected based on technological, sanitary, hygienic and economic indicators.

A modern forced ventilation system in an apartment, office, factory or any other facility provides comfortable indoor climate conditions.

Specification of ventilation systems

Ventilation systems differ in the method of stimulating air masses: gravitational (natural air exchange) and mechanical (forced air exchange). Mechanical systems are also divided into groups:

  • according to the functions performed - exhaust mechanical ventilation systems, supply systems, combined (with or without a recuperator);
  • by type of design - ducted, ductless, monoblock, stacked;
  • for the serviced object - general exchange and local.

Air exchange standards and air flow at objects for various purposes are regulated by current regulatory documents: GOST 30494-2011 (public and residentialbuildings), GOST R EN 13779-2007 (non-residential premises), SNiP 31-01-2003, SanPiN 2.1.2.1002-00.

Let's take a closer look at the types, designs, advantages, disadvantages and operating features of mechanical ventilation units.

Types of ventilation systems

1. Air handling units

Purpose - supply to the facility and purify street air with the possibility of heating/cooling and drying/humidifying (if necessary). The air flow is supplied through air ducts (channels) directly into each room. Due to excess pressure, air escapes through various leaks in windows, doors, walls and ceilings.

A general supply mechanical ventilation system is usually installed in residential buildings or country houses. And it works in conjunction with natural exhaust ventilation.

*IMPORTANT! One of the serious disadvantages of this system is the need for electrical or water heating of the entire volume of supply air, which at the design temperature of the winter period can reach tens of kilowatts.


For example, for an inflow with a volume of 500 m 3 /h, this volume can be considered normal for a typical office space or country house with an area of ​​150-200 m 3 /h. So the power to heat the air from -26°C to 22°C will be about 8 kW! Taking into account the use of electricity, this will be quite expensive with a constantly running ventilation system. Otherwise, you will have to reduce the total flow of incoming air.

Supply system diagram

2. Exhaust units

They are used for air exchange by mechanical removal of air and its inflow through leaks in windows and walls. The exhaust system can also be local and/or general.

The weak point of such systems is the lack of air supply from outside and the resulting imbalance of outgoing and incoming air flow. Therefore, operating exhaust and supply systems separately is not always effective. More often, supply and exhaust (combined) systems with balanced performance are installed.

Diagram of a forced exhaust system

3. Air handling units

Provide simultaneous air inflow and removal. Such a circuit supplies, filters, heats supply air (this is especially important in cold weather), dehumidifies or humidifies (if this is necessary for technological standards or any other reasons). At the same time, air is forcibly extracted from the room, which heats the incoming flow through a recuperator, which allows saving up to 70% on the energy costs of the entire ventilation unit.

When operating an air handling unit, it is possible to ensure the creation of excess or reduced pressure relative to atmospheric pressure. This feature is used, for example, in health institutions to improve comfort during certain procedures.


Ventilation units with recuperator

The advantage of such installations is saving electrical energy and reducing heating costs, since the incoming flow is heated partially due to the heat of the outgoing one. Additional heating is carried out in a water or electric heater.

In cottages, such installations are usually installed in utility rooms or attics. In offices, these can be technical rooms or corridors.


Duct installations and ductless ventilation

A ducted mechanical supply and exhaust ventilation system is used to supply air from the street and remove exhaust air through an extensive network of air lines. The system, taking into account a large distribution network of air ducts, is of course more expensive, but it allows you to distribute air exchange across rooms and floors depending on the specified conditions.

We can talk about a ductless ventilation system only if it is designed for one specific room. Whether it's a large workshop or a small bedroom.A ductless system does not require ductwork. It is characterized by ease of installation, operation and relatively low cost, but of course does not provide uniform air distribution.

Monoblocks and typesetting devices

In monoblock installations, the equipment is located in a single block. They differ in that the characteristics of the supplied air are already calculated in advance by the manufacturer and you only need to select the necessary installation. Such machines are easy to install and operate.Most often used on small and simple objects.


Typesetting systems are distinguished by their complexity and the necessary qualifications for their selection. The advantage of this type is that for each object it is possible to calculate and select the necessary and most suitable system elements for this particular object. Prefabricated units can be of any size, power, configuration, etc.

They are often used on large and complex objects with the required parameters.

Main components and components

In mechanical installations, various air handling devices are used: fans, heaters, dehumidifiers, humidifiers, filters.

Fans- This is the main element of the ventilation unit. Characterized by performance and generated pressure. They are divided into axial and radial;

Air ducts- designed for dividing air flows throughout the premises;

Filters- trap dust and clean incoming air from various contaminants;

Heaters- heat fresh street air before supplying it to the room. Heating is carried out using electricity or hot water;

Ventilation valves- protect the system from the penetration of air masses from the street when the system is turned off during cold periods due to a significant temperature difference inside and outside the room;

Ventilation grates- external grilles prevent foreign objects from entering the network, internal grilles distribute air flows and also perform decorative functions.

New— intelligent (“smart”) ventilation

The main disadvantage that characterizes a forced supply and exhaust ventilation system is the inability to regulate the air flow in accordance with the constantly changing parameters of the air environment in the room. Often air exchange takes place more intensively than necessary, wasting energy. In addition, air quality is determined not only by its temperature and humidity, but also by the concentration of carbon dioxide (CO 2) in it, coming from residents, office workers and other sources.

“Smart” ventilation, controlled by real needs, does not have this drawback. In addition, it is easily integrated into air conditioning systems and heating circuits, as well as into the overall smart home control scheme with remote control function.

The operating mode of intelligent ventilation is adjusted using temperature, carbon dioxide and humidity sensors. The intensity of air exchange is regulated at each individual facility based on the number of people present there. The system is configured according to a specific schedule (day of the week, time of day) and optimal power with the ability to select the temperature regime of the air flow.

When compared with conventional solutions, intelligent ventilation provides significant savings in electrical energy, while qualitatively solving the problem of maintaining the required microclimate characteristics.

For a more efficient and functional placement of system components, it is designed before construction or major repairs. To summarize, it can be noted: a “smart” mechanical ventilation system is not the cheapest, but the most effective method of air exchange. The costs are justified quickly enough thanks to heat savings and the use of automatic control of air parameters.

Ventilation is one of the main engineering systems of modern buildings. If in residential buildings it is not yet as popular as the norms require, then in public and industrial buildings it is designed and installed almost everywhere.

Let's take a closer look at what types of ventilation there are, how these systems are classified and how they differ?

Modern ventilation systems come in different types and, depending on their purpose, are divided into several subgroups. This division is carried out according to several parameters: the direction of air movement, the method of bringing air masses into motion, the territory served.

Ventilation in the house

What kind of ventilation is there in rooms in the direction of air movement? According to this parameter, systems are divided into two large groups:

  • inlet;
  • exhaust

There is also ventilation and its classification according to the factor that sets the air in motion. According to this parameter they are divided into:

  • with natural impulse (natural);
  • with mechanical motivation (mechanical, forced).

There is also a division of ventilation, the types of which vary depending on the service area. According to this principle, ventilation systems are divided into:

  • general exchange:
  • local (local).

All types of ventilation systems considered can be used both separately and together in one building or even room.

Systems can also be classified as ducted or ductless, depending on whether they use ductwork or move air through openings in the walls or fans without pipes attached.

Let us examine in more detail all the types and subtypes of room ventilation systems, how they differ and what their tasks are.

Natural ventilation

As already mentioned, natural ventilation is one of the popular types of modern systems. This type of room ventilation implies that the air is driven by natural factors. More precisely, it is the pressure difference between the internal volume and the external atmosphere. For it to function, it is necessary that the pressure outside is slightly less than inside the room. If such a factor occurs, air begins to move through specially designed ventilation ducts.

Natural ventilation

A striking example of such ventilation is the installation of exhaust ducts in the walls of multi-storey and private houses. The main positive factor in using natural ventilation is its low cost. There is no need to use expensive equipment or organize an electrical connection. Air exchange occurs on its own. But you need to keep in mind that there are also negative sides to using such a system. First of all, this is a dependence on atmospheric parameters.

Ventilation ensures the removal of excess heat, moisture, harmful gases, vapors and dust from the air of industrial premises. Ventilation removes polluted or overheated air from a room and replaces it with clean or cool air.

Regulation of ventilation and heating devices is set out in regulatory documents of national and industry significance (SNiP 2.04.03-91; SanPiN 2.2.4.548-96; GOST 12.1.005-99 SSBT).

Depending on the method of moving air in a room, industrial ventilation is divided into natural and mechanical.

With natural ventilation, air exchange in the room occurs due to the difference in temperature and specific gravity of indoor and outdoor air, as well as the influence of wind. This type of ventilation is called aeration. Aeration of premises is calculated and controlled natural ventilation.

It is known that the indoor air temperature is higher than the outdoor air temperature.

The volumetric mass of air Рτ (kg/m3) is inversely proportional to its temperature:

Рτ = Р/(1 + α t).

Here P is the volumetric mass of air at 0°C and a pressure of 760 mm Hg. Art., equal to 1.293 kg/m 3; a is the coefficient of volumetric expansion of air equal to 0.004; t - set air temperature, 0°C.

With aeration, air exchange in a building occurs due to the fact that warm indoor air, containing industrial hazards, under the pressure of colder outside air, exits through built-in shafts through deflectors installed above the shafts on the highest part of the roof.

The industry produces several types of deflectors. The TsAGI deflector has found the greatest application (Fig.)

Rice. TsAGI round deflector: 1 - pipe; 2 - bell; 3 - body; 4 - umbrella; 5 - foot for attaching an umbrella

It consists of a diffuser, the upper part of which is covered by a cylindrical shell. The umbrella covers the mine from precipitation. At the level of the bottom of the shell, a cone is attached to the diffuser, which prevents wind from penetrating inside the deflector. The wind flowing around the deflector shell creates a pressure lower than atmospheric pressure, as a result of which air moves up the shaft, which then comes out through two annular slots between the shells and the edges of the cone.

The advantages of natural ventilation: simplicity, low cost of installation and operation, high efficiency of air purification. The disadvantages include: the inability to heat, humidify or dry the incoming air; difficulties in uniformly supplying fresh air to all work areas and removing contaminated air directly from places where industrial hazards occur.

Wind pressure is generated by air flowing around a building. In this case, an increased pressure is created on the windward side, which promotes the flow of air into the room, and on the leeward side, a reduced pressure (rarefaction) is created, which promotes the exit of air from the room (Fig.).

Rice. Aeration scheme under the influence of wind pressure

To ensure better air exchange, prevent exposure of workers to cold air and eliminate the possibility of colds, air flow into the room is provided in the warm season at a height of no more than 1.8 m from the floor, and in the cold season - no lower than 4 m from the floor. To do this, two rows of transoms are placed along the height of the side openings of the building.

To ensure normal meteorological conditions in industrial premises, when designing industrial enterprises, along with natural ventilation, mechanical ventilation is provided.

With mechanical ventilation, air exchange is achieved using a fan. Therefore, this type of ventilation allows you to change the parameters of the air entering the room - heat, cool, dry and humidify, as well as purify polluted air emitted into the atmosphere.

The choice of ventilation scheme to create an indoor air environment that satisfies established hygienic standards and technological requirements depends on the purpose of the building, its number of floors, the nature of the premises and the presence of industrial hazards.

Based on the site of action, mechanical ventilation is divided into general and local.

General ventilation is designed to reduce the concentration of harmful impurities in the volume of the entire room to a standardized value. It can be supply, exhaust and supply and exhaust.

The most effective is supply and exhaust ventilation (Fig.), consisting of two separate systems - supply and exhaust, which simultaneously supply clean air into the room and remove polluted air from it.


Rice. Scheme of supply and exhaust ventilation with air recirculation: a - supply system; b - exhaust system; 1 - air intake device; 2 - air purifier; 3 - centrifugal fan; 4 - heater; 5 - humidifier-cooler; 6 - distribution pipeline; 7- supply nozzles; 8 - local suction; 9- dust collector; 10- ejection device; 11 - air duct; 12- valves; 13 - production premises; 14 - fan

Supply and exhaust systems in the room must be placed so that fresh air enters those parts of the room in which the amount of harmful emissions is minimal or completely absent, and the exhaust system is installed where emissions are maximum.

The volume of air flow into the room must correspond to the volume of exhaust air, the difference between these volumes should not exceed 10 ... 15%. This condition must be observed to avoid the formation of a vacuum in the room, especially in the winter and cold transitional seasons. The use of recirculation is unacceptable for rooms in which there are unpleasant odors, as well as when harmful substances are released into the air, which, according to the degree of impact on the body, belong to the first three hazard classes.

The volume of ventilation air is determined for each room depending on the type and amount of harmful substances released into the work area.

Air flow should be determined separately for the warm and cold periods of the year, taking the larger of the values ​​with a supply air density of 1.248 kg/m3.

When several types of inert gases or non-toxic dust (flour, starch, etc.) are emitted in a room, the required amount of ventilation air is determined for each type of hazard separately and takes a higher value. When several toxic gases, solvent vapors (alcohols, ethers, acetic acid, etc.), irritating gases (sulfuric and sulfur dioxide, hydrogen chloride and hydrogen fluoride, etc.) are released, take the amount of ventilation air calculated for each gas separately.

In table The values ​​of heat and moisture release in public catering establishments are given.

Heat dissipation (sensible), W/h

Source of heat and moisture release

Heat dissipation (sensible), W/h

Boiler, capacity;

per 1 m2 in plan

200 l, diameter 0.8 m

per 1 m 2 frying room

surfaces

50 l, diameter 0.5 m

Fire plate No. 1 (in

plan 3.87 x 1.67 m)

Frying and pastry shops

The same, No. 19(1.68x0.72 m)

cabinets GKSh-3 and ShK-20

The same, No. 21 (2.4 x 1.14 m)

Gas fryer UZhG-

Kitchen electric stoves

G1 or electric

(per 1 kW installed

power)

Various electrical appliances,

Gas stoves for restaurants,

except for boilers,

sectional

stoves and boilers (1 kW

Restaurant gas stove

installed power)

with cabinet for 8 burners

Steam lines (per 1 kg of steam)

The same, for 12 burners

People (per 1 worker)

The same, for 16 burners

Curtain walls above the stove

Digester capacity, l:

(per 1 m 2 glazing)

Processed

products on plates (on

Moisture release from cooking

boilers depending

from their capacity, (kg/h):

Bain-marie (per 1 m2 in plan)

Steam cabinet (per 1 m 2 in

Confectionery oven (per 1 m 2

outer surface)

When determining the heat and moisture release of equipment, the coefficient of simultaneity of equipment operation is taken equal to 0.8.

Heat release in the room from equipment installed under the curtains is taken equal to 20% of those given in the table; moisture release is not taken into account.

Moisture release per worker is taken to be 0.16 kg/h; per 1 kg/h of products processed on plates - 0.40 kg/h.

When calculating air exchanges in the trading floors of canteens, cafes and restaurants, the heat emission per visitor or employee is assumed to be 116 W/h, including the heat emission of food. Heat and moisture release from equipment installed in the premises is taken with a coefficient of simultaneous operation of equipment for canteens and cafes of 0.8; for restaurants 0.7. For the flow of supply air from the hall to the kitchen through the distribution and ventilation openings, the air speed is allowed to be no more than 1 m/s. Distribution openings are designed to span the entire width of the room. Additional ventilation openings are made at a height of 2 m. Regardless of the presence of local suction in washing departments and kitchens, exhaust from the upper zone is required at least once.

In industrial catering premises it is not allowed to supply air in the summer without appropriate treatment (cleaning, cooling, drying, etc.), and in the cold season - unheated. The required air exchange is checked during the transition period of the year at an outside air temperature of +10 ° C and a relative humidity of 70%. When determining the supply air temperature, it is necessary to take into account its heating in the fan by 1 ... 2 °C.

For rooms in which sudden release of large quantities of harmful or explosive substances is possible, emergency exhaust ventilation is provided. When vapors and gases heavier than air are released, the intake openings of ventilation systems are placed at a height of 0.3 ... 1.0 m from the floor level; when vapors and gases that are lighter than air are released - in the upper zone of the room. If the movement of explosive vapors and gases by fans is unacceptable due to their properties, emergency ventilation systems with ejectors are provided (Fig.).

Rice. Ejector: 1 - suction pipe; 2 - fan; 3 - pipe through which working air is pumped; 4 - nozzle; 5 - diffuser; 6 - pipe for suction of polluted air; 7 - exhaust pipe

The principle of operation of the ejector is that air, pumped by a compressor or high-pressure fan located outside the ventilated room, is supplied through a tube to the nozzle and, leaving it at high speed, creates a vacuum due to ejection in the chamber into which air is sucked from the room. The diffuser serves to convert dynamic pressure into static pressure. The disadvantage of the ejector is its low efficiency, not exceeding 0.25.

The air exchange rate during emergency ventilation should not be less than 8 h -1.

To compensate for the air removed by emergency exhaust ventilation, additional supply ventilation systems should not be provided.

Along with general working and emergency ventilation, local exhaust ventilation has become widespread in public catering establishments.

The main elements of local exhaust ventilation are local suction, a fan, a network of air ducts and air purification devices. Local suctions are divided into three groups: closed, semi-open and open.

A device for removing gases released from the desulfitator is shown in Fig.

Rice. Device for local removal of gases from a desulfitator: 1 - desulfitator; 2 - slot (H = 60 mm); 3 - opening half of the lid; 4-exhaust shaft with a cross-section of 250x250 mm, located 3 m above the roof; 5 - fixed half of the cover

In Fig. a local shelter with a roaster hood is shown.

Rice. Shelter with hood from the frying oven: 1, 2 and 3 - doors; 4 - pipe; 5 - bends

The frame, made of corners, is reinforced with sheet steel casing. The sides of the shelter are equipped with doors for easy servicing of the stove. At the top of the shelter there is a pipe with an outlet, which is connected to an axial fan and mounted on the same axis with the electric motor. The operation of the fans ensures the removal of the required amount of air from the shelter based on the creation of a flow velocity of 0.1... 1.0 m/s in the cross section of open openings.

Similar shelters are installed over onion cutters, cooking pots and other equipment.

Fans are used to move air in mechanical ventilation systems (with pressure losses in the network up to 15 kPa). According to the principle of operation, they are axial, centrifugal and diametrical. Depending on the pressure developed, centrifugal fans are divided into groups of low (up to 0.981 kPa), medium (0.981... 2.943 kPa) and high (2.943... 11.8 kPa) pressure. Fans are selected according to the required performance and total pressure; for a centrifugal fan, the type of drive and direction of rotation are also taken into account.

Based on the estimated volume of ventilation air (m 3 /h), the fan performance is determined. Next, local and total pressure losses are determined, then the fan number, rotation speed and power of the electric motor on the shaft are selected.

To normalize the air environment in the working area of ​​heat-using equipment of public catering establishments, air showering is carried out. When air showering, the air can be cooled or humidified; the air speed at the outlet of the shower pipe should not exceed 3.5 m/s.

The most effective means of normalizing the air environment of industrial premises is air conditioning.

Air conditioning- this is the automatic maintenance of predetermined optimal (comfortable) air parameters in the room, regardless of weather conditions and changes in technological conditions of the production process.

Based on the method of processing and supplying air to workplaces, air conditioners are divided into central and local.

Central air conditioners are installed in specially designated rooms. The air prepared in them, which meets the optimal microclimate conditions, is distributed throughout the workshops of the enterprise through an air duct system.

In local air conditioners, air is prepared directly in the serviced premises, and the air is supplied to workplaces without air ducts.

In a central air conditioner, air enters the first intermediate section through an insulated valve and then into the inlet separator-drip separator. From here, outside air enters an irrigation chamber equipped with nozzles. To prevent droplets from being carried away from the irrigation chamber, a second separator is installed at its outlet. Next, the air enters the mixing chamber, to which outside air is supplied through an air duct. The amount of this air is automatically regulated by an automatically driven globe valve. The air processed in the irrigation chamber, mixed with outside air, is freed from dust in a self-cleaning oil filter. Through the second intermediate and transition sections, this mixture enters the fan.

At the outlet of the fan there is a second set of pass-through valves with an automatic drive. These valves regulate the flow of air through the duct system. The volume of water for the irrigation chambers is located in the tank, and it is supplied to the nozzles by a pump through pipes. The air conditioner sections are installed on special cast iron stands.