Local ventilation is an air exchange system in a limited part of a space, the microclimate of which differs from its general atmosphere. That is, in fact, this type of ventilation is intended for installation at a separately considered workplace.
If the ventilation problems that the premises and its purpose pose to the specialists of VeerVent LLC can be solved by the method of general and local ventilation, they always choose the latter option, since it not only has high efficiency, but compared to the general exchange analogue it is much more economical in terms of electricity consumption. But according to performance separately local system ventilation, without general exchange supply- exhaust system, little effective. HVAC designers estimate this efficiency from 40% to 70%, from the required 95-100%, since the health of personnel depends on the local exhaust system.
In rooms with local emissions of harmful substances, the use of local ventilation allows you to reduce the amount of supplied and exhausted air several times!
Types of local ventilation
To create a ventilation system in the workplace, one of two types is formed - exhaust or supply local ventilation.
Exhaust local ventilation is used for localized sources of harmful substances, when it is possible to prevent their spread throughout the production area. It consists of capturing and removing harmful emissions released into the indoor air. With its help, the emission of dust, smoke, and gases is organized.
Supply local ventilation is designed for intensive supply directly to the workplace fresh air, cooling it if necessary, as well as blowing cooled air currents if significant thermal radiation occurs.
But local ventilation should not be considered a panacea for all types of buildings. Our specialists assess the premises, identify the tasks that are set for ventilation, when implementing an industrial project ventilation systems primarily guided by the expected effectiveness, economy and feasibility of using a particular method. Thus, local ventilation is not always able to remove harmful substances from the room at the proper level and eliminate them; in this case the best option there will be a combination of elements of general and local ventilation.
Methods for creating local ventilation
To remove harmful emissions from localized areas of the premises (local exhaust ventilation), shelter cabinets, curtains, side exhausts, casings near machines, umbrellas, etc. are formed.
To create fresh local ventilation, air oases and air curtains are organized. Air oases are movable partitions with a fairly large height (up to 2.5 m), into which cooled air is pumped. Air curtains- these are fan heaters installed near stoves, working windows, gates, etc.
Application of local ventilation
Local ventilation in many cases is justified, and often simply objectively necessary. It is used in almost any industrial sector, including mines, chemical, and metallurgical industries.
Depending on the type of source of hazards (machine, bathtub, etc.), various local suctions, exhaust hoods, exhaust panels, etc. are used. Onboard suctions, for example, are conveniently located around the perimeter of the bathtubs.
Benefits of local ventilation
These include, first of all, environmental necessity associated with maximum effective protection health of workers in hazardous production. With its help, they prevent the occurrence and development of pulmonary and cancer diseases, allergies, irritation of the eye mucosa, and headaches.
The second significant advantage is the economic efficiency of its use. It consists of saving energy costs (up to 60%), as well as increasing the productivity of working personnel (according to statistics - up to 20%). In addition, local ventilation contributes to additional heating of the air in the production room, which creates another savings item.
We recommend solving problems with exhaust air emissions, starting with the design of ventilation systems. Systems with several local suction and umbrellas require accurate calculations, which will allow the project to be implemented economically, and starting from the project engineering systems a strategic opportunity arises to plan the construction or reconstruction of systems.
Ventilation systems are provided in all modern buildings to remove polluted air. However, such exhaust systems often fail to clean the air. This problem is especially acute when it is necessary to remove heavily polluted air from storage facilities, workplaces in factories and other large premises with sources of air pollution. It is also common to install hoods in domestic settings, for example, in the kitchen, smoking room or dressing room.
An important condition for the effective functioning of exhaust ventilation is correct selection fan If the power of the selected fan is too high, neighbors living above will experience reverse thrust, which will cause the flow of exhaust air along with dust from the ventilation system into their ventilation grilles.
There are general exhaust ventilation, which provides air exchange for the entire room, and local exhaust ventilation, installed directly at the workplace.
Exhaust ventilation works in dirty rooms, and supply ventilation works in clean rooms. But for the best effect, mixed ventilation is usually installed, that is, supply and exhaust ventilation.
Forced ventilation
Supply systems are designed to supply clean air into rooms to replace polluted air. If necessary, the supply air can be subjected to such types of processing as cleaning, heating, humidification, etc.
The supply ventilation system consists of:
- air intake device
- heater
- cooler
- filters for cleaning
- room air supply devices
This system includes air supply units using 100% fresh air. They are like industrial purposes(used at industrial facilities) and domestic (apartment ventilation).
Supply units can be monoblock or stacked. Prefabricated systems are assembled from individual components, and the main advantage of such systems is the ability to ventilate any premises - from small apartments and offices to trading floors, supermarkets and entire buildings. But their disadvantage is the need for professional calculations and design and their large dimensions. Monoblock systems are housed in a single sound-insulated housing. The advantage of such a system over typesetting is a much lower noise level, which allows them to be placed in residential premises.
Typically, a supply ventilation system is used together with an exhaust system, and such ventilation is called supply and exhaust ventilation.
Supply and exhaust ventilation
Supply- exhaust ventilation is a combination of a supply system and an exhaust system, which allows it to combine the advantages of both one and the other systems. This system allows you to organize as much as possible correct air exchange
Supply and exhaust ventilation effectively solves the problem not only with air exchange, but also with filtration, regulation of temperature and humidity in the room. The system works at any time of the year. However, if the performance of both supply and exhaust ventilation is not balanced, drafts will begin to “walk” around the house and doors will slam.
In addition, supply and exhaust ventilation can significantly reduce operating costs through the use of heat recovery to heat the supply air. Heating of the supply air occurs due to the exhaust air room temperature(and in industrial premises, for example, workshops, the air can be much warmer) in a special heat exchanger - a recuperator.
Along with other advantages supply and exhaust ventilation one can also note its ability to create controlled under or overpressure compared to external environment, which is useful for people sensitive to changes in atmospheric pressure.
Supply and exhaust ventilation with heat recovery is mainly used in offices, cottages, swimming pools, cinemas, hotels, cafes and restaurants and in industrial premises.
Mechanical ventilation
Mechanical ventilation involves the use of fans, air heaters, dust collectors and other energy-consuming installations designed to move air over long distances. This type of ventilation is used where there is not enough natural ventilation.
Compared to natural ventilation, mechanical ventilation is much more expensive to operate due to increased energy consumption and more complex maintenance. However, the advantage of artificial ventilation is that fresh air can be transmitted (and dirty - removed) from local areas of the room in any required volume to the distances required for this. Also, this ventilation system has the advantage of being able to various processing(cleaning, heating, humidifying, etc.) of the air entering the room, which is almost impossible with natural ventilation.
The supply and exhaust systems of such ventilation, controlled by maintenance personnel, can be turned off at any time, and the operation of mechanical ventilation does not depend on weather conditions. For all these reasons artificial ventilation has become much more widespread than natural.
Natural ventilation.
Unlike forced ventilation and air conditioning systems, the main advantage of natural ventilation is cost-effectiveness, since the system does not use energy-intensive ventilation equipment and the naturalness of the air entering the room. No less important advantages of natural ventilation are its compactness, since the system does not clutter up the area, and its low cost - it does not require large installation and maintenance costs.
Duct and ductless ventilation
According to their design, ventilation systems are divided into 2 types: ducted and ductless. Duct-type ventilation systems have networks of branched air ducts that allow fresh air to be supplied or polluted air to be removed from the different parts same room or in different rooms. Ductless ventilation systems are installed on the roof directly above the ventilated room (for example, in large industrial premises) or in door and window openings. Demon duct system ventilation does not have a network of branched air ducts, and therefore such ventilation does not require large electrical costs. Also, unlike a duct (ventilation) system, a ductless ventilation system is easy to install and operate. Duct ventilation and ductless ventilation can be either mechanical or natural. Minus natural system Ducted or non-ducted ventilation is that such ventilation is not controlled - it is designed to prevent people in the room from suffocating.
Local ventilation
Local, or localized, ventilation removes harmful substances from the room directly in the place where the greatest accumulation occurs.
Local ventilation can be supply or exhaust.
Local supply ventilation designed to supply fresh air to certain places. It is capable of fully ensuring the flow of fresh, purified and, if necessary, heated or cooled air to the areas that need it. Local supply ventilation includes:
Air showers (supply a concentrated stream of clean air to work areas to cool work areas and reduce temperature environment);
Air oases (fenced off rooms into which air is supplied at a low temperature);
Air curtains (change the direction of air flows from stoves, gates, etc.);
Local exhaust ventilation designed to remove contaminated air from places with the highest concentration of harmful impurities (gases, smoke, dust and heat generated from equipment) in the air. The greatest effect is achieved when the places where harmful emissions are released are localized, which means they can be prevented from spreading throughout the entire room. Local exhaust ventilation includes shelters in the form of cabinets, umbrellas, side exhausts, curtains, shelters in the form of casings for machine tools, etc.
Local ventilation requires significantly lower costs than general ventilation, but if the release of harmful substances is dispersed, it is not effective.
General ventilation
General ventilation is installed when it is necessary to remove heat, moisture, gases, dust, odors or vapors from the air of the entire room or most of it. General ventilation systems are used only in cases of minor excretion harmful factors and their uniform distribution throughout the entire volume of the room. General ventilation can be supply or exhaust. General supply ventilation used to remove excess heat and moisture, as well as to dilute harmful impurities in ventilated air. In addition, general supply ventilation is designed to provide calculated sanitary and hygienic standards designed to ensure free breathing of a person in the work area. When the air temperature in the room is insufficient, general supply ventilation is installed with a mechanical drive, which makes it possible to heat the air and, as a rule, clean it of dust. When harmful emissions enter the workshop air, the amount of supply air must fully compensate for general and local exhaust ventilation.
General exhaust ventilation designed to remove air contaminated with harmful substances from a ventilated room. The simplest example of general exhaust ventilation is a separate axial-type fan with an electric motor on one axis, which is located in a window or in a wall hole. This installation removes air only from the area of the room closest to it, thereby performing only general air exchange. Some other installations of this type have an exhaust duct. If the air duct length is more than 30-40 meters and the pressure loss is more than 30-40 kg/m2, a fan is installed centrifugal type. If harmful emissions in workshops or other ventilated rooms are heavy gases or dust and there is no heat generation from equipment, exhaust air ducts are laid on the floor or in the form of underground ducts. Ventilation industrial buildings where there are various harmful emissions (heat, moisture, gases, vapors, dust, etc.) and their entry into the room occurs in different conditions(concentrated, dispersed, at different levels, etc.) is carried out using both exchange and exhaust ventilation. In certain cases, ventilation in industrial premises, along with mechanical ventilation systems, uses systems with natural impulse, for example, aeration systems.
With all the variety of ventilation systems, due to the different purposes of the premises, the different nature technological processes, types of harmful secretions and other factors, they can be classified according to the following criteria:
- Depending on what method of creating pressure for ventilation processes is used. They can be with natural or mechanical motivation.
- Depending on the purpose, the system can be supply, exhaust or supply and exhaust.
- Depending on the area served by the system - local and general exchange.
- Depending on the design ventilation can be ducted or non-ducted.
Considering these varieties, various combinations of ventilation systems are possible. For example, a general exchange duct system with supply and exhaust ventilation and mechanical drive (this is standard ventilation used for large climate systems) or a ductless local exhaust ventilation system with natural impulse (this is air exhaust without the use of a fan, operating naturally air convection).
Natural ventilation
This type of ventilation works thanks to:
- temperature differences between ambient air and indoor air (aeration);
- the difference in pressure of the air column between the serviced room and the exhaust device;
- influence of wind pressure.
Aeration is used in workshops with large heat releases, provided the permissible concentration of harmful gases and dust in the supply air in the work area is not exceeded.
Aeration is not used if, according to the conditions of the workshop technology, it is necessary to pre-treat supply air or if due to influx atmospheric air condensation or fog forms.
In ventilation systems in which air moves due to the pressure difference of the air column, the height difference (minimum) between the intake level internal air and its exit through exhaust device must be at least 3 m.
The recommended horizontal length of air duct sections should not be more than 3 m, and the speed of air movement in the air duct should not exceed 1 m/sec. If these requirements are not met, ventilation will simply not work effectively.
The effect of wind pressure is expressed in the fact that on the windward sides of the building (facing the wind) increased pressure is formed and, conversely, on the leeward sides - reduced pressure (rarefaction).
If there are openings in the building enclosures, then the outside air enters the room from the windward side and leaves it from the windward side, while the speed of its movement in the openings depends on the speed of the wind blowing the building and, accordingly, on the difference in pressure that occurs.
The natural ventilation system is simple and does not require electricity or expensive equipment. But since the efficiency of using this system depends on external variable factors (air temperature, wind direction and speed), more complex functions in the field of ventilation cannot be solved with their help.
Mechanical ventilation
These ventilation systems use equipment and devices (electric motors, dust collectors, air heaters, automation, etc.) that allow you to move air masses long distances.
The electrical energy consumption for operating this equipment is usually quite high.
Mechanical ventilation allows air to be drawn into and out of the right quantity from local areas of the room, regardless of changing atmospheric conditions outside the building. If necessary, the air can be exposed in various ways processing (cleaning, moistening, heating, etc.), which is impossible in a system with natural impulse.
It should be noted that very often in practice so-called combined ventilation is provided - this is the simultaneous use of natural and mechanical systems. This can significantly improve ventilation efficiency and reduce resource costs.
Forced ventilation
Forced ventilation serves exclusively for supplying air masses to the ventilated room. IN necessary cases The air is subjected to special treatment before it is supplied to the room - humidification, purification, heating, cooling, etc. Its removal occurs due to the occurrence overpressure in which excess air is forced out and replaced with fresh air. Air leaves the room through opening doors and leaks in building envelopes.
Exhaust ventilation
The task of exhaust systems is to remove contaminated or heated treated air from a room (production, workshop, building) to create a vacuum in it. Due to rarefaction, outside air enters through the doors and leaks in the enclosures.
Supply and exhaust ventilation
Depending on the desired effect, only a supply system or only an exhaust system can be used. But in most cases, both systems are provided in the premises at once.
Using supply and exhaust equipment, room ventilation has the following advantages:
- there is no residual pressure in the ventilated room;
- there are also no drafts.
On the one side, this type ventilation is quite powerful and is able to provide the necessary air exchange. On the other hand, air handling units are not very expensive in terms of electrical energy consumption and operating costs.
General and local ventilation
The purpose of general ventilation— ensuring air exchange throughout the room. With such a system everything required parameters air masses are maintained throughout the entire volume of the room. In addition, its tasks include the removal of pollutants, excess heat and humidity that were not eliminated by local ventilation to the permitted standard.
The local ventilation system is as follows: clean air is supplied to specific places (this is supply ventilation), and polluted air is removed only from places where unacceptable harmful emissions are formed (this is exhaust ventilation). Such a system can be suitable for a large room with a small number of people in it; in this case, air exchange is carried out only in areas where working people are located.
Duct and ductless ventilation systems
Ventilation systems may have a large, extensive network of channels (ducts) that are designed to move air. Such a system is called a channel system. Also, these channels may be absent, in which case the ventilation is called ductless.
Installation of a system with a channel network is used mainly in large rooms. As for ductless, it is used when installing small-sized systems, for example, a home fan.
The choice of ventilation system should be made at the design stage of the building (structure). And this, of course, should be done by professionals.
Local supply ventilation systems supply fresh air directly to workplace or to a place of rest. In the system's coverage area, conditions are created that differ from the conditions in the entire room and satisfy the requirements. Local supply ventilation includes air showers and oases. An air shower is a local air flow directed at a person. In the area of effect of the air shower, conditions are created that are different from the conditions throughout the entire room. With the help of an air shower, the following parameters can be changed: human mobility; temperature; humidity; concentration of one or another harmfulness. Air showers are most often used in hot shops, in workplaces exposed to thermal radiation.
Local supply ventilation also includes air oases - areas of premises fenced off from the rest of the room by movable partitions 2.0 - 2.5 meters high, into which air with a low temperature is pumped.
Local ventilation requires less cost than general ventilation.
General exhaust ventilation
Exhaust ventilation is used to remove contaminated or heated exhaust air from an industrial or residential premises (workshop, building). If premises are equipped only with an exhaust ventilation system, air is removed from the premises in an organized manner. The influx occurs unorganized or through leaks in building structures, or through holes specially provided for these purposes.
Exhaust ventilation (Fig. 2) consists of a cleaning device 1, a fan 2, a central 3 and suction ducts 4.
Unlike supply ventilation systems, in rooms with only exhaust systems, the pressure is set below atmospheric or lower than in neighboring rooms.
If there is only an exhaust ventilation system in the room, as in the case of supply ventilation, air flows from a zone of high pressure to a zone of low pressure. Thus, the movement of air in the opposite direction is eliminated or hampered. The most “dirty” rooms are equipped with exhaust ventilation systems when it is necessary to prevent or reduce the spread of air from them into neighboring rooms.
Rice. 2. Diagram of the exhaust ventilation system
Local exhaust ventilation
Local exhaust ventilation is used in a situation where the places where harmful substances are released in the room are localized and it is possible to prevent their spread throughout the room. Local exhaust ventilation in industrial premises ensures the capture and removal of harmful emissions: gases, smoke, dust, suspended matter and heat partially released from equipment. To remove harmful substances, local suction is used (shelters in the form of cabinets, umbrellas, side suction, shelters in the form of casings for machine tools, etc.).
Basic requirements that they must satisfy:
If possible, the place of formation of harmful emissions should be completely covered;
the design of the local suction must be such that the suction does not interfere normal operation and did not reduce labor productivity;
harmful emissions must be removed from the place of their formation in the direction of their natural movement (hot gases and vapors must be removed upward, cold heavy gases and dust - downward).
The air removed from the room during local exhaust ventilation must first be cleared of dust before being released into the atmosphere. The most complex exhaust systems are those that provide for a very high degree of air purification from dust with the installation of two or even three dust collectors (filters) in series.
Local exhaust systems, as a rule, are very effective, as they allow you to remove harmful substances directly from the place of their formation or release, preventing them from spreading throughout the room. Due to the significant concentration of harmful substances (vapors, gases, dust), it is usually possible to achieve a good sanitary and hygienic effect with a small volume of removed air.
Entering any premises, be it an apartment, office, production, medical or educational institution Without even noticing it, we determine whether the ventilation system is working well. Of course, the first words will not be “how poorly the ventilation works,” but “oh, how heavy the air is in this room.” And when the ventilation is in good order and works well, a person does not feel any foreign odors and feels good.
Types of ventilation: general approach
So, ventilation is an engineering system that is designed to provide air exchange that maintains a certain temperature and humidity regime. Unlike other systems, ventilation is able to function without the use of any equipment and devices, based on physical laws. Its main purpose is to supply clean air filled with oxygen into the room and remove waste air saturated with carbon dioxide.
The need to maintain a certain regime in any room makes the ventilation system the most popular of all engineering systems. Existing classification divides ventilation systems into four categories:
- According to the effect of air exchange (natural, forced).
- Mixed (supply, exhaust).
- Zonal (general exchange, local).
- By construction (with channels, without channels).
Ventilation and its types have their own characteristics, although they all have the same purpose - to create a favorable microclimate for a person’s comfortable living and work. The question of what system the construction site will be equipped with is considered at the design stage.
In order to understand the purpose of a certain type of ventilation, you need to understand their features. After all, from the right choice depends on the conditions for proper operation. For a certain room, building regulations provide for its own special humidity and temperature regime.
Purpose of supply and exhaust ventilation: advantages and disadvantages
The most common ventilation system is one with natural movement of air flows. It copes well with its functions of supplying air supplied with oxygen and removing waste materials, if nothing interferes with their movement. The principle of its operation is based on physical laws:
- the difference in temperature and pressure inside and outside the room;
- difference in pressure in the room and in the place installed hood(usually on the roof);
- wind pressure.
The advantages of the supply and exhaust system are that its installation does not require special equipment. Absence ventilation devices does not include their maintenance or electricity costs.
Flaws:
Firstly, the presence of factors that interfere with the correct operation of the system:
- Metal-plastic or wooden sealed windows and doors.
- The ventilation duct is clogged with debris, snow, waste products of birds, and their nests.
- Freezing, therefore, reduction or complete blockage of the exhaust pipe during the cold season.
- Wrong arranged hood above the roof, which causes it to fall into the wind pressure zone. Therefore, the exhaust pipe must rise above the roof ridge by at least 50 cm.
- IN multi-storey building– neighbors may disturb the ventilation duct during repairs.
- Reverse thrust can be “organized” by a powerful kitchen hood, which interrupts the flow of exhaust air towards the sanitary rooms and begins to draw not only gases and vapors from the kitchen, but also from the ventilation openings.
Secondly, since the operating principle is based on temperature differences, ventilation works correctly only in the cold season or at night.
Important! This ventilation system is installed during construction apartment buildings. Exhaust openings, in accordance with building regulations, are placed in the kitchen, bathroom and toilet rooms.
Mechanical and mixed ventilation: their brief characteristics
Mechsystem
Mechanical ventilation is an improved natural ventilation, that is, supply and exhaust processes are performed using special equipment (fans, electric air heaters, filters, recuperators, and sometimes ionizers). The disadvantages of such systems are: expensive equipment; complex installation; dependence on network voltage; electricity costs.
The main advantage is correct operation at any time of the year, regardless of temperature. In addition, the air coming from the street is cleaned of harmful impurities and heated to comfortable temperature(if the system contains an air heater or recuperator).
Combisystem
Mixed ventilation consists of supply and exhaust ventilation, in which one of the natural flow processes is replaced by forced ventilation. Supply ventilation helps improve the process of supplying fresh air to the room. Mechanical (window or wall) supply valves) or electrical (fans, air handling units).
Exhaust fans are exhaust fans. They are installed in ventilation holes in sanitary rooms, they are also installed in the kitchen, in the wall with access to the street. Such devices significantly improve air exchange. A basic hood for a private home consists of: a valve; fan; exhaust shaft; electric motor; air duct; deflector.
Important! A mechanical ventilation system is effective for installation in private houses, where it is difficult to maintain the required microclimate on several floors. This system works successfully in rooms with a swimming pool.
Zonal ventilation: types
This is a rather specific system with several areas of application. What are the features of the system types?
A local supply ventilation system delivers clean air to specific workplaces and lowers the temperature in a given area. With the help of such an influx they reproduce air barriers or change the direction of air flows.
The general exchange inflow assimilates excess heat and moisture, diluting harmful fumes that were not removed by zonal exhaust. If the incoming air is not warm enough, then install a heater. Such systems work where it is necessary to ensure circulation throughout the entire room or most of it.
Local exhaust is used to remove waste and contaminated air flows from certain places. It is used in production workshops, entertainment centers, where it is important that carbon monoxide, dust, and smoke do not enter other rooms. The following is used as exhaust system equipment:
- side suction;
- umbrellas;
- curtains;
- casings;
- cabinets.
General exchange hood – exhaust unit with powerful fan, removing waste air masses from the rooms where it is installed.
Important! Zone ventilation systems are installed in industries where there are harmful emissions. It is not advisable to install them in apartments or private houses.
The designs of ventilation systems differ in the presence of channels for air exchange and without it, when the devices are built-in (wall, window). Ductless systems mainly correct the incorrect operation of natural ventilation in apartments. Duct systems are installed in cottages, industrial premises, and offices. Air moves through channels consisting of air ducts and fittings.
