It is not always possible to get the necessary air flow through windows and doors, sometimes weather conditions prevent this. And that is why special devices are created - ventilation complexes that provide a solution to such a problem. But a huge variety of practical conditions leads to the fact that these systems are divided into a number of types.
Normative documents
Such an important type of communication as ventilation is strictly regulated by regulations. Key requirements are contained in SNiP 41-01-2003. As the developers of the act themselves say, it regulates:
- environmental characteristics;
- impact on the sanitary situation in the building;
- fire safety level;
- energy saving;
- stability of work under design conditions.
All these points must be strictly ensured, regardless of the specific format of ventilation and the range of tasks it solves. Recently, more and more attention has been paid to the improvement of mechanical ventilation and its connection with air conditioning systems. The creators of SNiP relied on the provisions of GOST related to:
- acoustic safety (12.1.003-83);
- properties of air in working and residential premises (12.1.005-88);
- standard cross-sectional dimensions of air equipment (24751-81);
- microclimate in residential and administrative buildings (30494-96).
The standard requirement for air supplied to living rooms is warming up to at least 15 degrees Celsius in winter. In public buildings and administrative facilities, at least 12 degrees of heat is required. And in the production workshops, air supply is not allowed, the temperature of which would be less than 5 degrees. The design task may provide for lower air temperatures during the cold season. All pipelines are installed only so that they can be easily repaired or replaced.
All air inlet openings may be placed at least 1 m above a stable snow line. This parameter must be determined taking into account the data of meteorological services that control the state of the weather in a particular area. Where there are sandstorms, it is necessary to surround these chambers with devices that trap harmful particles. Air intake systems must be separate for each fire compartment. When calculating air demand, the largest figures are taken as a basis.
System classification
By way of submission
According to this parameter, natural and artificial types of ventilation are distinguished. Natural movement is provided by:
- temperature differences between the outside and the air in the house;
- pressure differentiation between the room and the deflector on the roof;
- pressure created by the wind.
The first option is best used where a lot of heat is generated. Most often we are talking about production workshops, the air of which contains a small amount of toxic gases and dust particles. Aeration will have to be abandoned if it requires sophisticated preparation of incoming air, as well as in the case when its intake provokes the appearance of fog, condensation. Natural ventilation, working with the help of pressure imbalance between two points, requires the creation of a difference in height of at least 3 m. It is advisable to install horizontal sectors of air ducts no longer than 300 cm, limit the rate of air movement to 1 m per second.
The wind system works in the case when the parts of the building turned to the wind are subjected to increased pressure, and in the opposite place it is reduced. Naturally, air rushes from a denser area to places where there is rarefaction; for it to get inside, openings in the fences are required. The faster the wind flow, the greater the pressure difference, and therefore the air will pass inward in a larger volume. Any of the described ventilation complexes is simple and does not require electric current. But since the driving forces are very unstable and the air pressure is quite small, it will not work to count on a successful solution to the entire spectrum of problems.
The way out is the use of special equipment that facilitates and accelerates the movement of air over significant distances. Increased possibilities of mechanized ventilation often result in significant costs for electrical energy. You can extract air from certain places or add it as needed, regardless of unstable environmental conditions. Another advantage is the possibility of complete processing, including increasing moisture or removing contaminants. To eliminate the occurrence of problems, mixed ventilation is often used, which is capable of operating in forced or natural mode.
By appointment
This parameter allows you to select supply and exhaust complexes. The names already eloquently characterize their essence. Thanks to the supply equipment, it is possible to ensure the receipt of clean outdoor air instead of the removed mass. In certain cases, the incoming air is treated (cleaned, made more humid or heated). Exhaust systems are designed to remove the exhaust part of the air.
In practice, these two types of systems are used simultaneously., trying to ensure a balance between the intake of air and its discharge to the outside. There are cases when only an exhaust or inflow is mounted. In such situations, the main structural openings of the room itself or adjacent parts of the building are used to exchange air with the external environment. Developers can provide for the inflow and removal of the exhaust gas mixture for the entire facility as a whole. But sometimes their placement is used only in certain areas.
According to the way of air exchange
There are such types of air exchange as local, general, emergency, fire and combined options. Any system that supplies portions of air to specific places or removes contaminated mass from individual problem areas just falls into the category of local ventilation. Air showers are considered a variant of a local influx. Like their water counterparts, they direct the flow in a concentrated manner, increasing its speed. Basically, such systems are needed to reduce the heating of the workplace and cool the people themselves who are at risk of heat stroke.
The so-called air oases are also quite widespread. They are formed by separating certain parts of the room from the rest of its volume using mobile partitions. Each oasis must be supplied with a relatively cold (compared to the main mass) air flow. Air curtains are often used in industrial facilities where there are fixtures and machines that create high temperatures. The undoubted advantage of local ventilation is that it is more economical than capital systems.
But the use of such complexes in all parts of buildings is not always appropriate. After all, this significantly complicates the design and installation, requires careful coordination of separate ventilation segments with each other. Therefore, even in serious enterprises, the main role belongs to the general system. Local blocks are used only at those workplaces where there is a need for a special circulation mode. As for local exhausts, they are needed so that from local sources of pollution they do not seep into the rest of the building.
Many variants of removing localized systems have been developed:
- umbrellas;
- veils;
- suction cabinets;
- casings on individual machines and so on.
Suction devices are subject to very strict requirements. So, we must try to cover all the space that is clogged. If this is not possible, it must be ensured that the largest possible part of the installation generating harmful substances is drained. Further, suction must necessarily exclude interference with the full-fledged work of the enterprise as a whole and its individual employees.
To reduce energy consumption, it is required to send harmful substances to the same place where they would go on their own. Not open, but semi-open suctions are preferred. Their advantage is that a much smaller volume of air is required to purify the atmosphere. Local exhausts must be equipped at the input with devices that remove dust. Important: if the workflow covers the entire room as a whole or involves the movement of people, a common ventilation system is needed.
The common exchange apparatus allows you to evenly draw air out of the room or evenly distribute it.
The following main tasks are solved:
- elimination of excess heating and moisture;
- reduction of dangerous volumes of gaseous substances;
- maintaining the sanitary standards provided for by the design calculations;
- providing comfort for workers in certain places.
If, during data collection for a project, it turns out that there is not enough heat in the room, the general ventilation inflow should be equipped with mechanical accelerators and devices that warm the air. In this case, it is desirable to free the air mass from dust. After all, any heating equipment, with rare exceptions, only increases its quantity. And if the dust particles fall into an open fire or on a heated surface, an unpleasant odor may appear. Since in a number of industries emissions contain gases of high density, dust, and the equipment itself almost does not emit heat, in such cases floor or underground pipelines are installed.
But many industrial facilities work in such a way that many different types of harmful substances appear. At the same time, they usually enter the room unequally. In such a situation, it is necessary to combine local and general ventilation. Separately, these two systems will not cope, even if their design and installation are carried out flawlessly.
By design
natural and mechanical
It is useful to take a deeper look at the differences between natural and mechanized ventilation. In any case, you first need to calculate the intensity of air exchange, find out what the cross section of the air channels should be. It is generally accepted that the natural type of ventilation is more comfortable for people. In addition, the flow rate limitation allows you to almost not be afraid of drafts. Namely, this factor is the "initiator" for many respiratory diseases.
But the problem is that the reduction in air velocity requires (with the same volume of it) an increase in the size of the channel. This not only complicates the work and increases the cost of it. Often it is simply not possible to apply pipelines of the required size. This creates technical or design difficulties. Therefore, it is impractical to simply refuse mechanical devices.
What is common between natural and mechanical air movement is that you need to think about its flow inside a house or a large building. Typically, this goal is achieved by installing special gratings in the doors on the desired flow path. Professionals believe that the dirtiest place should be purged last. For a residential building, such a zone is a sanitary unit; it is preceded by a kitchen.
If the grill option is not suitable, you can leave a gap from the bottom of the door to the floor. Its value must be uniform - at least 2 cm along the entire length, regardless of the type of flooring and the purpose of the rooms connected by the opening. When there is no grate (gap), no investment in the ventilation system will be justified. If the bathroom has an extractor fan, the build-up of pressure will make it harder to open the door. Important: when taking into account the natural flow of air, it is necessary to take into account that part of it that makes its way through cracks and holes in external walls, in other structures.
If wooden leaky windows are installed (and they still remain in many places), in an hour after 1 sq. m of their surface will pass inside up to 20 kg of air. In private houses and apartments, the area of which does not exceed 150 square meters. m, this is enough to meet hygiene needs. Especially when you consider that some inflow goes through loose joints on the doors and even through the walls. If the rooms are glazed with modern plastic, aluminum windows, they are much more hermetic. But here it is already necessary to introduce amendments for the intensity of ventilation and micro-ventilation in accordance with the manufacturer's documentation.
General exchange with a mechanical drive
supply type
The supply type of construction for the most part have a channel design and consume a fairly significant amount of electricity. But a full supply of air is provided even to the most inaccessible places. Therefore, the costs of arranging such communications pay off in the shortest possible time. Since the speed of pumping air using mechanical systems is quite high, the inflow must compensate for everything that the outlet has taken. An exception is made only for places where there are toxic or foul-smelling substances.
At such points, less air is necessarily added than is extracted from there. To compensate for the difference, pumping is used through windows or from areas where the atmosphere is cleaner. The basic components are:
- intake apparatus;
- cleaner;
- ventilation heater;
- fan;
- air lines;
- pipes for nozzles with the necessary nozzles.
There are situations when it is not necessary to heat the incoming air. In this case, it bypasses the heater and moves along a bypass route. In the design process, supply mechanical ventilation is mainly equipped with clean or almost clean rooms. Ejectors or conventional fans can be used to pump air. The choice between them in a particular case is made for engineering reasons.
General exhaust
General exchange exhaust - in the process of calculating such systems, the goal is to find a configuration, which would allow, after replacing the displaced air, to reduce the concentration of harmful substances to the MPC level or less. Use of systems with the extended air ducts is allowed. When the total length of such a pipeline is more than 30-40 m, it is legitimate to fear excessive pressure losses. You can compensate for them by replacing axial fans with centrifugal ones, which drive air more strongly. In some cases, elements that provide aeration come to the aid of the general exchange exhaust system.
Supply and exhaust
The supply and exhaust option stands out in comparison with the already mentioned excellent performance. There are two ways to form a supply and exhaust system.
In the first scheme, the air is mixed like this:
- a fan spinning at high speeds draws in fresh portions from the street;
- in the room, old and new air are mixed;
- the excess escapes through a special valve and a pipe connected to it.
To place the fans, choose a position under the ceiling or on it. But there is another solution, which involves pushing out the exhaust air with a flowing mass. Here fans with a low speed of rotation will already be required, and they are placed at the bottom. An exhaust pipe is mounted on the outer wall, which is connected to the exhaust valves using special channels. Valves and channels are located on top.
When the fan is running, new portions of air are sucked in from the outside. That part of it, which is already in the room, has time to warm up. At the same time, it becomes lighter, rises to the ceiling, where it is mechanically pushed through the valve. It's easy to see why this design works best in homes with high ceilings. In order not to provoke a pressure difference, the extraction and suction elements must be very well balanced, otherwise their work will be poorly coordinated.
An important point: the formation of areas with increased pressure helps to prevent the ingress of bad odors from kitchens and bathrooms into adjacent rooms. In these places, the inflow should be more active than the air exhaust. In most regions of Russia, it is appropriate to supplement supply and exhaust ventilation with heat recovery means. These devices alone reduce the total heat loss during the removal of air masses by almost ¼. In fact, the recovery is provided by heat exchangers, in which the outside air absorbs part of the heat from the outgoing mass without mixing with it.
The next logical step is to equip the heat exchanger units with devices that increase air humidity and additional filters. But the problem is that not all specialists can mount even simple devices. Moreover, it will not be possible to create ventilation with your own hands, which uses a heat exchanger with additional options. They also complicate the calculation and subsequent maintenance. So before making a final decision, you need to weigh all these circumstances.
In case of an accident
If you need to dismantle the broken ventilation and then restore it, you need to approach the matter very seriously. First you need to find out what type of box is installed in a particular room. The decisive test, which accurately determines serious malfunctions, is carried out by hand, without the involvement of experts. You just need to see if the light deviates towards the air channel or not.
Restoration work begins with the analysis of ceilings and walls. It is very important to select exactly those materials that meet standard requirements. Most often, gypsum slabs and blocks based on foam concrete are used. You can not overly narrow the ventilation duct, so as not to do work from scratch. The convenience of individual materials does not justify their use to form ventilation.
Against smoke
Fire ventilation plays a special role. Smoke removal is especially important in rooms actively used by people and on escape routes. First, an evacuation plan is drawn up, and only then, in accordance with it, a smoke-exhausting ventilation scheme is prepared. Corresponding systems should be made separate from other devices. It is imperative to install smoke ducts:
- in commercial establishments;
- in high-rise buildings of any kind;
- in administrative buildings;
- in office buildings, educational and cultural institutions;
- in hotels and hostels.
Recently, amendments have been made to the federal regulatory framework, requiring the installation of smoke channels in underground parking lots, public garages and warehouses. Smoke extraction structures must ensure:
- quick, unhindered and efficient evacuation;
- saving is possible longer than the integrity of the property;
- maintaining relatively favorable (as far as possible during a fire) conditions for the actions of emergency rescue teams;
- blocking the movement of gaseous and solid combustion products inside the building, their exit to the outside.
High pressure air injection is often practiced. This is ensured by the use of special fans. Depending on the specific conditions, harmful substances can be drawn out both naturally and mechanically. But almost always they use special mechanics in order to speed up the work as much as possible and increase efficiency. Most often, checking the quality of installation of fire ventilation systems is combined with a training fire alarm.
Types of air ducts
The channels through which the air flows are divided according to:
- geometry;
- the material used;
- specific characteristics;
- block linking method.
The rectangular type of duct is practical, but inside the air forms vortices. If you use a rounded ventilated channel, the flow will begin to slide freely. This is only achieved if the surface is sufficiently smooth. As for the docking method, it determines the financial and time costs, and along with them - the quality of the seams created. If it is required to stretch a round pipe, a bandage is used.
For the production of pipes used:
- stainless and galvanized steel grades;
- polyethylene;
- metal-plastic;
- special fabrics;
- fiberglass;
- aluminum.
Decisive when choosing between these options are their thermal and mechanical resistance. The scope is determined by the rigidity of the structure. The pressure is considered low if it does not exceed 0.9 kPa. High pressure is declared over 2 kPa. Intermediate indicators belong to the middle category.
For residential and industrial premises
The differences between ventilation in these cases are not only due to the fact that there are few harmful reagents in the houses. The difference is due to the fact that the volume of air pumped is very different. In industrial buildings, ventilation should ensure the purification of the internal atmosphere from:
- dust particles;
- microscopic inclusions;
- toxic fumes.
More recently, in the room and even on the balcony, loose places in wooden frames were used for ventilation. But modern ventilation systems, although they are able to successfully replace them with full glazing, work well only in the case of high-quality insulation. First of all, it is required to insulate the structure from the outside in order to reduce the formation of condensate. The most common type of ventilation in this place is supply and exhaust valves, which:
- almost not conspicuous;
- occupy a minimum of space;
- eliminate the appearance of drafts;
- do not require power supply;
- controlled by simple devices.
The arrangement of ventilation ducts in the wall of a warm attic also has its own characteristics. Roof aerators direct the supply air mass in the area of the eaves. Most people choose soffits installed in the lower lobe of the eaves with special holes. Perforated constructions, letting in fresh breaths, block the passage of insects. Thanks to the spotlights, it is possible to form an impeccable look and guarantee functionality.
Cold attics are ventilated mainly by means that they create on their own. For this purpose, air is passed through:
- lattices and gable windows;
- roof ridges;
- skates;
- overhangs of cornices.
Channel and non-channel systems
Channelless ventilation devices do not give good results in all cases. Not even every apartment can be ventilated in this way. But garages, utility rooms - quite. If the building is divided into a number of zones that differ in their parameters, only channel complexes will have to be used. Important: the ductless configuration is quite compatible, like the one with pipelines, with mechanical and natural air circulation encouragement.
The natural channelless method of ventilation is, in principle, uncontrollable and does not allow you to control the process. In addition, it leads to significant heat costs. Mechanical inflow without the use of channels implies the use of either special fans or air conditioners. In execution, these are similarities to the already described oases and veils. Due to the high power of the necessary devices that drive the flow, it is necessary to install devices that dampen the sound.
Essential elements
Indispensable parts of the ventilation system include exhaust and air inlet openings. Their size is determined individually, taking into account the need for inflow and discharge. According to the size of the holes, both gratings and pipelines are selected. To hold open (hanging without solid support) sections, special brackets are used to press the channel against the wall or ceiling. The role of adapters is to connect pipes of different sections to each other, to form turns and intersections.
Controllers and control panels are mainly used in cottages and other serious facilities. Additionally, the following may apply:
- ceiling diffusers;
- gates;
Ventilation in various forms is present in almost all buildings and premises. In most cases, it is arranged to fulfill certain goals, but sometimes it occurs spontaneously, due to natural factors. Why is it needed, what are the principles of the device, the nuances and types of ventilation systems - we will consider these issues in more detail.
What are ventilation systems for?
The main purpose of ventilation is the organization of air exchange. It is designed to supply the required amount of fresh air and remove contaminants together with the exhaust air. The same is the result of poor ventilation.
Types of ventilation of premises depend primarily on the purpose of the objects themselves. According to this principle, the systems are:
- production;
- for public buildings;
- for residential premises.
Types of ventilation systems of these types perform slightly different roles. If systems for residential and public buildings are primarily designed to supply the required amount of oxygen together with outdoor air and remove people's breathing products, then industrial ventilation is often calculated to remove harmful substances in the first place, with compensation of the removed air by outdoor air.
In addition to the scope of the air ventilation system, it is also classified according to other parameters.
Types of ventilation
Types of ventilation in buildings are primarily divided according to the direction of movement. They are supply and exhaust. In general, the volume of supply and exhaust air should be equal. This ratio is called air balance. It is necessary so that the removed amount of air is completely replaced by fresh air, otherwise a vacuum occurs or, conversely, increased pressure due to a large intake of outside air squeezes it out through the cracks in the windows and leaks in the doors.
The placement of the supply and exhaust system depends on the requirements for the premises. Optionally, in each room or room, both the inflow and the exhaust are satisfied. For example, types of ventilation in residential buildings come with such an arrangement of equipment that the exhaust is carried out in technical rooms (bath, toilet, kitchen), and the inflow is supplied to the living rooms. The movement of air from supply to exhaust devices passes through the slots under the doors or through specially arranged grilles in them.
In addition to the direction of movement, ventilation is classified into the following types:
- according to the mechanism of inducing air to natural and artificial (mechanical);
- serviced areas into general and local.
natural
Types of natural ventilation are primarily classified into supply and exhaust. In fact, there is only natural exhaust ventilation, which works under the influence of the pressure difference between the atmospheric air and the air in the room. And the influx already arises as an effect of replacing the removed air, it occurs as a result of rarefaction of the air in the room.
The natural ventilation scheme consists mainly of vertical ventilation ducts in the walls, which must be of sufficient length for draft to occur. What systems are often used in residential multi-storey buildings or private cottages.
Types of ventilation of industrial premises also include natural systems in various combinations. Also in such buildings, aeration is widely used, which in essence is ventilation when installing window or ventilation openings from different sides of the building.
Previously, supply ventilation in natural systems mainly occurred through leaks in windows and doors under the action of an exhaust hood, but with the spread of vacuum double-glazed windows and energy-efficient windows, this mechanism has practically disappeared. Because of this, ventilation does not work properly, it is not enough. To solve the problem in the absence of centralized systems, supply valves are used in or which allow a certain amount of air to be supplied to living rooms for people to breathe.
Mechanical
Artificial ventilation differs from natural ventilation in that mechanical devices are used to set the air in motion. These are electric fans of different types and devices. Fans are:
- radial, in which the impeller moves in the same plane with the air flow;
- axial - the impeller perpendicular to the air flow.
The following types of artificial ventilation can be distinguished:
- supply;
- exhaust;
- supply and exhaust
If the first two types are also characteristic of natural systems, the supply and exhaust is a purely mechanical area. Their peculiarity is that the equipment for both branches is the same.
Mechanical systems include not only fans, but a large number of other equipment: filters, heaters (electric and water), heat pumps, valves, dampers, grilles. It is necessary to regulate the air flow, cleaning and heating it.
Types of mechanical ventilation are also classified according to the layout of the system. It can be either a prefabricated system, when the fan and all other elements are selected separately and assembled already at the facility, or monoblock, when all these elements are assembled at the factory into one housing (heat and sound insulated) and delivered to the facility. The first type is cheaper and more flexible, but monoblock devices are more convenient to install. They do not require additional configuration. Most often they come with built-in automation.
Supply and exhaust
Consider separately supply and exhaust systems. This is a relatively new type that is designed to improve the energy efficiency of equipment. The purpose of ventilation systems of this type is similar to supply and exhaust. The main difference is that all elements (primarily fans) are arranged in one device and are interconnected during operation.
There are two large groups of such systems:
- without recovery;
- with recovery:
- with lamellar(cross-flow heat exchanger);
- with rotary heat exchanger;
- with freon heat pump as a recuperator;
- with glycol recuperator.
Devices without recuperation differ little from separate supply and exhaust systems, mainly with matched fans to ensure the same air flow. Devices with heat recovery are modern and efficient equipment, the peculiarity is that the arrangement of equipment for both branches in one housing allows reducing energy consumption.
Recovery is the return of heat from the exhaust air back to the room. During the operation of a conventional system, exhaust air is removed from the room, irrevocably carrying away heat. And the outside cold air supplied to the room in winter requires constant heating. This leads to an overexpenditure of energy resources for heating. Recovery partially solves this problem. The heat from the exhaust air is transferred to the supply air with the help of recuperators.
Plate heat exchangers
lamellar(cross, cross-flow), in which air moves in a special package of aluminum, paper or copper plates, where the inflow and exhaust do not mix. The second name appeared because of the direction of air movement - they seem to intersect. Differ in average efficiency about 80%.
Rotary heat exchangers
Rotary air handling units. They have a rotor made of a material with good heat capacity, which slowly rotates along an axis located between the supply and exhaust branches. During rotation, part of the rotor is heated by the exhaust air. The heated part of the rotor during rotation moves to the supply zone and transfers heat to the cold air passing there. most efficient systems. In some cases, it can exceed 90%.
Heat pump recuperators
Rarely, but systems are still used with heat pump. They use a compressor and heat exchangers, which are located in the supply and exhaust branches. The compressor, as it were, pumps heat from the exhaust zone to the supply zone. Most often used for swimming pools, as they allow you to organize the removal of moisture.
Glycol recuperators
With glycol recuperator. By design, they are similar to a heat pump, only the heat is transferred from the exhaust branch to the supply branch not by freon, but by the coolant - a mixture of glycol and water. Their efficiency is not very high (up to 50%) and according to this indicator they lose to rotary and lamellar ones. Used mainly for large systems.
The efficiency of recuperation depends on the type of equipment and on the features of operation. Also, this parameter is influenced by the temperature and humidity of the air in both the supply and exhaust systems. Most often it is in the range of 70-80%, but sometimes even 40-50% already gives significant savings in energy resources.
The ventilation scheme in the house most often provides for a plate heat exchanger, less often a rotary one. Heat pumps have found their distribution in ventilation systems for swimming pools. Types of industrial ventilation that use recuperation include all sounded systems.
Local
The purpose of local ventilation is to serve a certain area in the room. They are used in order to reduce the need for air and reduce the cost of the system. For example, an exhaust hood over a typical domestic kitchen hood is local ventilation. What types of ventilation exist? Local systems are of the following varieties:
- Exhaust hoods over domestic and industrial cookers, hoods over welding stations, machine tools and other industrial equipment.
- Air showers, which are a local supply system and supply the required amount of air to the working area. For example, to a workplace in a shop.
The use of local systems reduces the cost of equipment and air heating.
General exchange
The general exchange system, unlike the local one, serves the entire volume of a room or building. For example, the types of ventilation in a private house are mostly general. They can be both mechanical and natural. In general exchange systems, it is important to properly distribute the air, for this you need to know the features of the room and the location of the working areas.
The hood is most often arranged in the upper zone, because warm polluted air often rises to the ceiling from where it is easier to remove. But in some systems, the hood must be arranged near the floor. This applies to industries where heavy gases occur. In the same garage, carbon monoxide sinks to the floor.
Also must take into account the location, people's jobs, beds and resting places.
The considered purpose and classification of ventilation systems allow you to generally orient yourself in this important engineering network and select the optimal equipment for your purposes.
Any building, or industrial, needs high-quality air exchange. It will not only ensure the supply of oxygen, but also protect structures from the growth of mold and fungus, and provide comfortable conditions for people to stay. Today we will talk about what are the disadvantages and advantages of ventilation systems. Types of ventilation, the specifics of its design and useful recommendations - in our today's material.
The fresh atmosphere in the room is a guarantee of the well-being of its inhabitants
Read in the article
Let's start with the basics: what is ventilation?
Ventilation is air exchange, regulated by a set of special devices.
Doctors have found that an adult healthy person inhales about 20 thousand liters of air per day on average. In order for us to feel normal and be able to work effectively, the air must have a certain chemical composition, including ions, phytoncides and the norm of ozone.
Air of this quality does not always naturally enter the premises. To establish this process, a ventilation system is used. It ensures the movement of air masses inside the room, and the removal of the exhaust atmosphere. The more intensive the operation of the premises, the more powerful the ventilation system should be.
Classifications of ventilation systems according to various criteria
Air exchange systems are divided into different types according to several criteria:
| Classification sign | Subspecies |
| On the organization of the movement of air flows | Mechanical |
| Natural | |
| By function | exhaust |
| Supply | |
| Supply and exhaust | |
| By service area | General exchange |
| local | |
| By design | Drier |
| Channelless |
Ventilation systems include a variety of equipment and can be combined with heating and noise reduction systems. Various types of air curtains, filters, silencers, air ducts, heaters, grilles of various shapes and valves are used for the air exchange process.
Consider the listed types of ventilation systems in more detail.
Fundamentals of natural ventilation
Natural ventilation in the house is carried out due to different pressure and temperature regimes inside and outside the building, as well as with the help of winds blowing around the building.
As a rule, the temperature in the room is higher than outside, for this reason, the exhaust air easily rises and leaves through the ventilation shafts, drawing in cooler masses from the outside.
In what cases is the channel and channelless system used?
The ductless complex does not need a network of air ducts. Atmospheric exchange occurs through holes in the wall - supply and. Air vents, gaps under doors and transoms can act as sources of fresh air. Channelless systems are suitable for living rooms. It is easy to install and requires no special maintenance or operating costs.
Duct ventilation needs an air duct. Its installation is justified if the air intake or supply must be carried out in an intensive mode and to a certain place in the room.
How to properly design a ventilation system
Algorithm of the main works:
- you need to study the sanitary standards for air exchange in residential premises, correlate them with the dimensions of your rooms;
- calculate the dimensions of the air channels;
- choose the optimal layout of air ducts;
- prepare places for the installation of structures;
- install all elements of the system.
If you thought about high-quality air exchange at the stage of designing a house, you did the right thing. It is at this stage that you can plan the placement of communications so that they are not noticeable and at the same time work with maximum efficiency.
The main mistake in planning ventilation systems is the installation of networks that are too powerful, which will lead to unjustified energy losses. Another unpleasant moment is the occurrence of reverse draft in the ventilation of a private house.
Fundamentals of calculating ventilation in a private house
It is necessary to start designing a ventilation system with the study of sanitary standards and the correct calculation. To calculate natural ventilation, the following sequence is used (all values are measured in cubic meters per hour):
- In accordance with sanitary standards, the required volume of air entering the premises is determined.
- By the same criteria, the volumes of the outgoing flow through the exhaust system are calculated.
- The two values obtained are compared and the larger value is taken for further calculations.
- Measure the height of the future common exhaust duct for natural ventilation.
- Based on the number and performance of channels from each room in the house, the dimensions of the common exhaust duct are calculated.
When calculating the air exchange, the work of a mechanical hood in the kitchen should be taken into account. In addition, special attention should be paid to calculations for the bathroom, toilet and rooms that do not have, such as a basement and a boiler room.
To simplify the calculations, you can use special calculators and programs. One of the most popular programs is Vent-Calc v2.0. How to work in it in several videos of detailed video instructions:
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It is permissible to install overflow valves from residential premises that do not have natural air exchange to rooms with ventilation.
Several schemes of ventilation systems for example:
When planning ventilation ducts, it should be borne in mind that their diameter cannot be less than 150 mm, and one side of a square pipe - less than 10 cm. Such a small 3-meter long duct will exhaust approximately 30 m 3 / hour.
Important! The length of all ventilation ducts on the floor should be the same, so the common duct is placed in the center of the building.
Usually, the diameter of the air duct from the premises is made standard, and the intensity of air exchange is regulated by ventilation grilles with controlled blades.
If your house has only one floor, there is no need to install a common duct in the center, as is done in multi-storey structures. You can bring all the channels to the head of the roof.
Tips for arranging ventilation in a private house
- Insulate ventilation ducts. Excessive cooling is fraught with condensation. In winter, this can lead to the formation of ice, in the summer - the appearance of an unpleasant odor.
- When planning your system, pay special attention to the aerodynamic characteristics of the ducts. Do not try to make them too narrow, make sure that the diameter of the channel does not change along the entire length, the channels cannot be located horizontally.
- Allow air exchange between living quarters with grilles and overflow valves. The area of such a valve is selected not less than 200 cm².
- Leave gaps under the doors in 1.5 - 2 centimeters in rooms without an exhaust hood.
- To improve the operation of the ventisystem, install blowers in the air ducts in damp rooms. In the bathroom and toilet room, you can mount these devices, then they will turn on only when a person is present.
- To ensure natural ventilation in the kitchen, connect a tee with a non-return valve to the kitchen hood. When the hood fan stops, the valve will open and allow natural air exchange.
- If the house has a basement or basement, be sure to install ventilation ducts there. This way you avoid dampness and save your floors.
- To reduce energy losses, use humidity and temperature sensors in the natural ventilation system, complete with adjustable valves and.
Article
Ventilation of premises is classified according to the following main features:
Natural and mechanical ventilation
Natural ventilation is a ventilation system that does not contain electrical equipment (fans, motors, drives, etc.). The movement of air in it occurs due to the difference in temperature, pressure of outdoor air and air in the room, wind pressure. Natural ventilation exists in all high-rise buildings - it is a system of vertical channels (air ducts) with ventilation grilles in kitchens and bathrooms. The air ducts are brought to the roof, where special nozzles are installed on them - deflectors, which enhance the suction of air due to the force of the wind. The inflow of fresh air should be carried out through the cracks in the doors and window openings, open vents. The efficiency of natural ventilation depends very much on random factors - wind direction, air temperature. In addition, over time, air ducts become clogged with dirt, dust, debris, and the flow of fresh air is noticeably reduced after plastic windows are installed in apartments.
Mechanical ventilation systems use equipment and electrical appliances that allow air to be moved over considerable distances, as well as, if necessary, to clean and heat it. Mechanical systems are able to provide the desired level of air exchange, regardless of external conditions, but they are not cheap, and the cost of electricity for their operation can be quite large.
In practice, the so-called mixed ventilation is often used, that is, both natural and mechanical. So, for example, sometimes it is enough to install small fans in the ventilation ducts in the kitchen and in the bathroom. There are "smart" fans with automatic control, for example, a bathroom fan that turns on when the humidity level exceeds a set limit, a toilet fan that connects to a light switch. And to improve the supply ventilation, you can install double-glazed windows with supply valves, through which, due to the difference in pressure and temperature, air from the street will flow. The valve is usually equipped with a diaphragm that regulates the amount of incoming air. It may also contain a filter to purify the incoming air, reduce the noise level.
In each specific project, only a specialist will be able to determine which type of ventilation is the most efficient, more economical and technically rational.
Supply, exhaust and general ventilation
Supply systems - one of the types of mechanical ventilation, are used to supply clean air to ventilated rooms instead of the removed one. Supply air, as a rule, is subjected to special treatment (cleaning, heating, humidification, etc.) with the help of appropriate additional equipment.
Exhaust ventilation removes polluted or heated exhaust air from the room (workshop, building). In the general case, both supply ventilation systems and exhaust systems are provided in the room. Their performance must be balanced with regard to the possibility of air entering adjacent rooms or from adjacent rooms. The premises may also be provided with only an exhaust or only supply ventilation system. In this case, the air enters the room from the outside or from adjacent rooms through special openings, or is removed from the room to the outside, or flows into adjacent rooms. Both supply and exhaust ventilation can be arranged at the workplace (local ventilation), or for the entire room (general ventilation).
Local ventilation is called such ventilation, in which air is supplied to certain places (local supply ventilation) and polluted air is removed only from places where harmful emissions are formed (local exhaust ventilation).
Local ventilation is less expensive than general ventilation. In industrial premises with the release of harmful gases, moisture, heat, etc. Usually, a mixed ventilation system is used - common throughout the entire volume of the room and local (local inflows) to supply fresh air to workplaces.
Local exhaust ventilation is used when the places of release of harmful substances and secretions 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 and heat partially released from the equipment.
For local extraction, local exhausts are used (shelters in the form of cabinets, zones, side exhausts, curtains, shelters in the form of casings near machine tools, etc.)
Local exhaust ventilation systems, as a rule, are very effective, as they allow the removal of harmful substances directly from the place of their formation or release, preventing them from spreading in the room. Due to the removal of a significant concentration of harmful substances (vapours, gases, dust), it is usually possible to achieve a good sanitary and hygienic effect with a small amount of air removed.
However, local ventilation systems cannot solve all ventilation problems. Not all harmful secretions can be localized by these systems. For example, when harmful emissions are dispersed over a large area or volume, air supply to individual rooms cannot provide the necessary air conditions. The same is true if the work is carried out on the entire area of the premises or its nature is associated with movements, etc.
General ventilation
General exchange ventilation systems - both supply and exhaust, are designed for ventilation in the room as a whole or in a significant part of it. General exchange exhaust systems relatively evenly remove air from the entire serviced premises, and general exchange supply systems supply air and distribute it throughout the volume of the ventilated premises.
General supply ventilation
General exchange supply ventilation is arranged to assimilate excess heat and moisture, dilute harmful concentrations of vapors and gases not removed by local ventilation and general exhaust ventilation, as well as to ensure design standards and free breathing of a person in the working area.
With a negative heat balance, that is, with a lack of heat, general exchange supply ventilation is arranged with mechanical stimulation and with heating of the entire volume of supply air. As a rule, before supplying the air is cleaned of dust. When harmful emissions enter the air of the workshop, the amount of supply air must fully compensate for general and local exhaust ventilation.
General exhaust ventilation
The simplest type of general exhaust ventilation is a separate fan (usually of an axial type) with an electric motor on one axis, located in a window or wall opening. Such an installation removes air from the room zone closest to the fan, performing only general air exchange.
In some cases, the installation has an extended exhaust duct. If the length of the exhaust duct exceeds 30-40 m and, accordingly, the pressure loss in the network is more than 30-40 kg/sq. m., then instead of an axial fan, a centrifugal type fan is installed. When harmful emissions in the workshop are heavy gases or dust and there is no heat release from the equipment, exhaust ducts are laid along the floor of the workshop or are made in the form of underground channels.
In industrial buildings, where there are heterogeneous harmful emissions (heat, moisture, gases, vapors, dust, etc.), and their entry into the room occurs under different conditions (concentrated, dispersed, at different levels, etc.), it is often impossible to get by with any one system, for example, local ventilation or general exchange. In such rooms, to remove harmful emissions that cannot be localized and enter the air of the room, general exchange exhaust systems are used.
Ducted and non-ducted ventilation
Ventilation systems either have an extensive network of air ducts for moving air (duct systems), or air ducts may be absent, for example, when installing fans in a wall, in a ceiling, with natural ventilation, etc. (channelless systems).
Stacked and monoblock ventilation systems
The most common are type-setting ventilation systems. They are assembled as a constructor from separate elements (fan, filter, silencer, air ducts, etc.), and the elements can be from different manufacturers. The type-setting system can be designed for any room, from a small apartment to an entire building, but only a specialist can correctly calculate and design it.
A monoblock unit is a complete ventilation system located entirely in one housing. In a monoblock system, a heat exchanger is often installed - a device in which heat exchange of cold supply air with warm air removed from the room takes place, which saves from 30 to 90% of electricity. Installation of a monoblock system takes several hours and does not require a large amount of consumables, but it will not be possible to fit it into every room.
Agitation ventilation and displacement ventilation
There are two main types of ventilation commonly encountered: mixing ventilation and displacement ventilation.
Before considering these two types in more detail, it is necessary to review the most commonly used air quality terms.
Ventilation efficiency
Ventilation efficiency is a measure of how quickly polluted air is removed from a room.
It is determined by the ratio of the concentration of harmful impurities contained in the exhaust air to the concentration of harmful impurities in the room.
Ventilation efficiency is often used as a qualitative measure of a system's ability to provide clean air comfort. This indicator depends on the geometry of the room, the relative position of the supply and exhaust openings, and the distribution density of sources of harmful impurities in the room.
Displacement ventilation makes it possible to obtain ventilation efficiency values above 100%, while mixing ventilation does not exceed 100%.
Air exchange coefficient
This parameter characterizes the rate of air replacement in the room.
It depends on the conditions of air distribution in the room, the location and size of diffusers, the location of heat sources, etc.
When applying the displacement method, it is possible to obtain values of the air exchange coefficient from 50 to 100%, while with mixing ventilation they do not exceed 50%.
Displacement ventilation
This is the most efficient method traditionally used in the ventilation of industrial facilities. In addition, this ventilation method has found wide application in so-called comfort ventilation systems. With a properly calculated scheme, this method allows you to effectively remove excess heat and achieve maximum ventilation efficiency.
For a more detailed description of this method, it is necessary to highlight the following concepts: working area and adjacent area
Work zone
The part of a room occupied or used by people.
The working area is considered to be a space spaced 50 cm from walls and window openings, and from 10 cm to 180 cm above the floor.
Surrounding area
This is the space around the supply low-velocity diffuser, where it creates a certain local air velocity. For comfort ventilation systems, it is generally accepted that the local air velocity in the adjacent area should not exceed 0.2 m/s.
Such requirements are imposed in order to reduce the adjacent area around the diffusers as much as possible.
Displacement ventilation draws air to the lower level and flows into the work area at low velocity. The supply air must be somewhat colder than the room air for the displacement principle to work.
For comfort systems, the supply air temperature should be 1°C below room temperature, and for industrial or special systems, this value is between 1 and 5°C.
If the temperature on the inlet is too low, there is always a risk of the formation of a so-called. convection currents.
Advantages and disadvantages
Displacement ventilation is very convenient for use in industry, where there are many harmful impurities and heat emissions.
Properly designed displacement ventilation systems provide very good air quality, but this principle has some limitations:
- Supply diffusers require more space;
- Supply diffusers can mistakenly cover something;
- The adjacent area becomes much larger;
- The vertical temperature gradient becomes very high.
When designing these systems, it is also necessary to take into account the relative height and power of heating devices, which affect the dynamics of air flows inside the room. When combined with extraneous air currents in the room, uneven heating in height in some cases causes the heated layers of air to move down. In practice, this leads to the functioning of the ventilation system according to a different principle - mixing
Agitation ventilation
In mixing ventilation, supply air is supplied in one or more streams to the working area, entraining a large amount of air inside the room. The working area lies in the return flow zone, where the air speed is 70% of the main air flow speed.
Jet length
Under the length of the jet, the distance from the air distributor to the cross section of the air jet is taken, in which the velocity of the flow core decreases to 0.2 m/s.
ejection
Ejection is the ability of diffusers to mix adjacent room air into the jet.
Jet-type diffusers (where air is swirled while passing at high speed through nozzles) are prime examples of high-ejection air inlets. Diffusers for displacement ventilation have a low degree of ejection.
To eliminate the feeling of draft when the supply jet temperature is below room temperature, it is necessary to use supply diffusers with a high degree of ejection.
Covering effect
When the ventilation hole is located in sufficient proximity to a flat surface, the outgoing air current deviates towards it and tends to flow directly over the surface. This effect arises due to the formation of rarefaction between the jet and the surface, and since there is no possibility of air admixture from the surface, the jet deviates towards it.
For the occurrence of a flooring effect, the distance between the air inlet and the ceiling should not exceed 30 cm.
Air speed and temperature
The acceptable air speed in the working area depends on such factors as: room temperature, type of activity in the room, interior design. It is noted that the feeling of draft is eliminated when the air speed is less than 0.18 m/s and the temperature is from 20 to 22 °C.
Obstacles
The airflow is likely to change direction when there are obstacles hanging from the ceiling, such as lamps, ceilings, etc. If the protrusion does not exceed 2% of the height of the ceiling, then the airstream will go around the obstacle.
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Ventilation- this is a set of measures and devices that provide controlled air exchange in industrial premises. Ventilation designed to provide sanitary (1) and technical (2) purposes.
(1) consists in maintaining indoor air in accordance with the norms of SNIP, GOST and general sanitary standards.
(2) It consists in providing a certain cleanliness, temperature, humidity and air velocity in the room, based on the characteristics of the technological process
Types of natural ventilation:
Organized - through special openings and structures.
Unorganized - through the looseness of the structure.
Wind pressure, thermal pressure
TO virtues natural ventilation include low operating and capital costs.
Flaws natural ventilation: not used in rooms where there is a release of substances, does not carry out cleaning before release into the atmosphere.
Advantages of artificial ventilation over natural:
Ability to supply and remove air in any room
Ability to supply air with any temperature, humidity and mobility
Possibility of uniform operation all year round
Possibility of local suction devices
The possibility of cleaning the air removed from the room
Ventilation system is a set of devices for processing, transporting, supplying and removing air. Ventilation happens : Natural, Mechanical, Mixed.
Natural ventilation systems - simple devices, but their operation depends on unstable factors: air temperature and pressure, wind direction and speed. With natural ventilation, it is impossible to heat, cool, humidify, dry or purify the incoming air.
In the event of a disruption in the technological process or the operation of any equipment and the ingress of a large amount of harmful or explosive substances into the air, emergency ventilation is usually provided - general exhaust ventilation, not compensated by an appropriate air supply, which creates rarefied air during its operation and prevents harmful substances from entering other rooms.
37, 38, 39. Mechanical ventilation. Advantages and disadvantages. The main schemes for organizing air exchange. General exchange - purpose and systems. Local - purpose and systems.
mechanical ventilation- Air is moved by fans.
Mechanical ventilation systems are divided into:
1) Flowing (pump air)
2) Exhaust (remove air)
3) Combined
According to the nature of the coverage of the premises, ventilation can be divided into:
1) General exchange. Carries out air exchange throughout the room and serves to dilute the emitted hazards with a fresh air stream.
2) Local. It is used to remove air pollution directly at the place of formation and does not allow the penetration of harmful substances into the entire room.
3) Combined systems. They are used in case of significant intake of harmful substances into the air.
Advantages mechanical ventilation: pre-treatment of air is carried out, the possibility of supplying and extracting air at any point in the room, the possibility of air purification. Flaws: high operating and capital costs.
When designing, the requirements of SNiP 2.04.05-91 "Heating, ventilation and air conditioning" and GOST 12.4.021-75 SSBT Ventilation systems are taken into account. General requirements.
General ventilation is: supply, exhaust and supply and exhaust.
Local ventilation is: supply and exhaust.
Supply ventilation scheme
1 - air intake device; 2 - air duct; 3 - filter; 4 - heater; 5 - fan; 6 - supply nozzles.
Forced ventilation is applied in industries with significant heat emissions and low intensity of emission of harmful substances, provided that the incoming fresh air ensures the dilution of harmful substances to an acceptable concentration.
Exhaust ventilation scheme
1 - Exhaust nozzles; 2 – fan; 3 - Cleaning device; 4 - Deflector.
Local exhaust ventilation is used to remove harmful substances directly at the place of their formation. It is more economical and efficient.
General exhaust ventilation can be used:
In the presence of minor leaks of harmful gases, vapors from closed equipment where it is impossible to equip local suction
Moisture and heat excesses
Removing dust.
Types of local exhaust ventilation:
Completely enclosed enclosures that cover the sources of emission of harmful substances.
Receivers that shelter sources of harmful substances, but have working windows for maintenance
Receivers that partially cover sources of harmful emissions from the production environment
Open air intakes, which are suctions of one design or another, close to the source of harmful substances.