In a room filled with fresh air, it is easier to breathe, it is more productive to work and sleep better. But opening the window for airing every 2-3 hours is problematic, do you agree? Especially at night, when all family members sleep sweetly.
One of the automated solutions for this problem is the supply and exhaust ventilation (UIP) of the room. But how to make it right? We will help you learn the principle of operation and deal with the features of the arrangement.
In this article, the constituent elements of the exhaust air-exhaust system, the rules for their calculation and the standards for air exchange in various types of premises are considered.
Arrangements have been made for the arrangement of ventilation, a photo with the image of individual elements of the system, useful video recommendations on the ventilation system in a private house with their own hands are given.
The content of the article:
- What is ventilation?
- Physical basis of the ventilation system
- Features of exhaust ventilation
-
Dynamic ventilation parameters
- Regulations on arrangement
- Formulas and explanations for them
- The specifics of the installation of mechanical ventilation
- Features of the construction of natural PVV
- Conclusions and useful video on the topic
What is ventilation?
How often do we air the room? The answer should be as honest as possible: 1-2 times a day, if you do not forget to open the window. And at night, how many times? A rhetorical question.
According to sanitary and hygienic standards, the total mass of air in a room where people are constantly must be completely updated every 2 hours.
Under normal ventilation understand the process of the exchange of air masses between a closed space and the environment. This molecular kinetic process provides the ability to remove excess heat and moisture using a filtration system.
Ventilation also ensures that the air in the room meets the hygiene and sanitary requirements that imposes its own technological limitations on the equipment that will generate this process.
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Supply and exhaust ventilation system is designed to implement air exchange activities, the result of which provides sanitary standards in the room
Actions that provide both an inflow of fresh air flow and the removal of exhaust air mass are needed mainly where intensive air exchange is required.
In supply-and-exhaust systems, devices that stimulate either the exhaust of air, or its inflow, or forcing and sucking air at the same time are combined.
All supply and exhaust ventilation structures belong to a mechanical category that requires the installation of technical devices and the use of electricity
Ventilation systems of supply and exhaust type can filter, irrigate, heat or cool the air. But air conditioners, which are often used as additional air-conditioning equipment, are much better at handling airflow.
Air ducts and ventilation systems equipment only in industrial buildings are laid in an open way. In commercial and residential premises they are hidden in attics or behind false ceilings, except for the loft style.
Traditionally, the assembly of air ducts was made from elements in the manufacture of which galvanized steel was used. Tin is still used in enterprises and buildings intended for public visits.
Ventilation ducts in private kitchens, country houses and on the premises of enterprises that do not require the construction of powerful systems are constructed of rigid, plastic and corrugated plastic pipes.
Channels of exhaust ventilation
Inflow and exhaust unit
Supply and exhaust circuits in industrial premises
Ceiling mounted ventilation channels
Ventilation work in tandem with air conditioners
Location of ventilation systems
Assembly of ventilation ducts from tin
Polymer vents and corrugations
The ventilation subsystem is a set of technological devices and mechanisms for air intake, removal, movement and purification. It is part of an integrated communications system for buildings and premises.
We recommend not matching concepts. ventilation and air conditioning - very similar categories, which have a number of differences.
- Main idea. Air conditioning provides support for certain parameters of air in a closed space, namely, temperature, humidity, the degree of ionization of particles, and the like. Ventilation produces a controlled replacement of the entire volume of air through the inflow and outlet.
- Main feature. The air conditioning system works with air that is in the room and there may be no fresh air at all. The ventilation system always works on the border of the closed space and the environment through the exchange.
- Means and methods. Unlike ventilation in a simplified form, air conditioning is a modular scheme of several blocks, which handles a small part of the air and thus maintains the sanitary and hygienic parameters of the air in the specified range.
System ventilation in the house can be expanded to any desired scale and provides, in the event of an emergency in the room, a fairly quick replacement of the entire volume of air mass. What happens with powerful fans, heaters, filters and an extensive piping system.
You may be interested in information on the arrangement of the ventilation duct from plastic ducts, discussed in our other article.
In addition to the main function, ventilation systems can be part of the interior in an industrial style, which is used for office and retail space, entertainment facilities.
There are several classes of ventilation, which can be divided with respect to the method of pressure generation, distribution, architecture and purpose.
Artificial injection of air in the system is carried out with the help of injection installations - fans, blowers. By increasing the pressure in the piping system, you can move the gas-air mixture over long distances and in considerable volume.
This is typical of industrial facilities. production premises and public facilities with central ventilation system.
The generation of air pressure in the system can be of several types: artificial, natural or combined. Often used the combined method
Consider ventilation systems local (local) and central. Local ventilation systems are “point” narrowly targeted solutions for specific rooms where strict compliance with standards is necessary.
Central ventilation provides the ability to create a regular exchange of air for a significant number of similar in purpose premises.
And the last class of systems: supply, exhaust and combined. Supply and exhaust ventilation systems provide simultaneous supply and extraction of air in space. This is the most common subgroup of ventilation systems.
Such designs provide easy scaling and maintenance for a wide variety of industrial, office and residential premises.
Physical basis of the ventilation system
The forced-air and exhaust ventilation system is a multifunctional complex of ultrafast processing of gas-air mixture. Although this is a system of forced gas transportation, it is based on quite understandable physical processes.
To create the effect of natural convection of air flow, heat sources are placed as low as possible, and the inlet elements in or under the ceiling
The word “ventilation” is closely related to the concept of convection. It is one of the key elements in the movement of air masses.
Convection is the phenomenon of the circulation of heat between cold and warm gas flows. There is a natural and forced convection.
A bit of school physics to understand the essence of what is happening. The temperature in the room is determined by the temperature of the air. Heat carriers are molecules.
Air is a multimolecular gas mixture, which consists of nitrogen (78%), oxygen (21%) and other impurities (1%).
Being in a closed space (room), we have a non-uniform temperature with respect to height. This is due to the heterogeneity of the concentration of molecules.
Given the uniformity of gas pressure in a closed space (room), according to the basic equation molecular kinetic theory: the pressure is proportional to the product of the concentration of molecules and their average temperature
If the pressure is the same everywhere, then the product of the concentration of molecules and the temperature in the upper part of the room will be equivalent to the same product of concentration and temperature:
p = nkT, ntop* Ttop= nbottom* Tbottom, ntop/ nbottom= Tbottom/ Ttop
The lower the temperature, the greater the concentration of molecules, and therefore the total mass of the gas. Therefore, it is said that warm air is “lighter”, and cold air is “heavier”.
Proper ventilation, combined with the effect of convection, is able to maintain indoors the set temperature and humidity during periods of automatic shutdown of the main heating.
In connection with the above, the basic principle of ventilation arrangement becomes clear: the supply (flow) of air is usually equipped from the bottom of the room, and the outlet (exhaust) - from above. This is an axiom that needs to be considered during the design of a ventilation system.
Features of exhaust ventilation
Supply and exhaust ventilation interacts with two different in composition and purpose air flow, which are subsequently processed.
In PVV all the necessary equipment and additional systems are placed in a single frame that can be installed inside the loggia, in the attic, on the wall outside the house, etc.
The special design of the installation provides ample opportunities to ensure the ventilation of practically any number of rooms in the building.
In addition to the main function of air movement, the supply and exhaust ventilation includes the following arsenal of auxiliary subsystems and additional functions.
Among which are the following:
- air cooling and heating;
- ionization and wetting of particles;
- disinfection and air filtration.
Consider a typical duty cycle ventilation and exhaust ventilation system, which is based on a dual-circuit model of transportation.
At the first stage, cold air is taken from the environment and warm air is drawn from the room. On both sides of the air passes the cleaning system.
After the cold air is transferred to air heater (heater) - typical for UIP with heat recovery. In addition, heat is transferred to cold gas from warm exhaust air — typical of conventional systems.
After heating and heat exchange, exhaust exhaust air is discharged through the external channel, and the heated fresh air is supplied to the room.
The popular layout of the ventilation module includes a heat exchange chamber (heat exchanger), in which thermal energy is exchanged between oncoming air flows. In any case, each stream passes through a double filtration system.
The main principles of supply and exhaust ventilation are efficiency and economy.
The classic scheme of exhaust ventilation has the following advantages:
- high degree of purification of the input stream
- affordable operation and maintenance of removable parts
- integrity and modularity of a design.
To expand the functionality, the air handling units are equipped with auxiliary control units and control, filter systems, sensors, auto-timers, silencers, overload alarms electric motors recuperative blocks, condensate trays, etc.
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In the composition of the air-exhaust system can be used separate installations, making or fence, or removal of air mass
In such cases, the air supply ducts of the supply branches of the systems are equipped with filter systems, sprinkler units and heaters. The equipment is installed close to the air points.
All devices involved in air treatment, including an exhaust fan, can be located in the same housing. Similar units are used at small enterprises, in private sport complexes and country houses.
In the design of exhaust installations there are no devices involved in the preparation of air for supply to the room. It is easier to install, maintain, operate.
Inflow installation on the facade of the house
Blocks with filters and heaters
Air handling unit
Exhaust installation in the service station
Dynamic ventilation parameters
A lot of questions are connected with the design of the ventilation system, since in case of an erroneous calculation characteristics of a completely economical ventilation system, you can get a wasteful "monster" energy resources.
What directly affects the financial costs of its maintenance. As a result, the idea of economical operation of the equipment itself is not considered.
The main load of the ventilation system falls on the fan. The performance of the fan depends on the shape of the impeller (wheels with blades), the quality of materials and equipment assembly
In order to properly design supply and exhaust ventilation it is recommended to make algebraic calculations of plant performance and dynamic parameters of air flow.
There are several different methods and algorithms for computing, but one of the simplest and most reliable options will be presented to our attention.
All that is associated with secondary processes of humidification, additional ionization and secondary treatment at this stage can be ignored.
Regulations on arrangement
Provide a complete list of sanitary norms and rules (SNiP), which are advanced to various ventilation systems irrational, since the material is enough for a couple of books, but to know the reference constants for residential and office space necessary.
With regard to office space, when building a ventilation system, the main attention is paid to those rooms where the office personnel will be located.
Further, all standards are indicated per person. In a classic office building on the same floor there is a complete set of various types of premises.
For example, in the office in one hour 60 cubes of air should be replaced, in the operating rooms - 30-40 m3in the bathroom - 70 m3, in the smoking room - more than 100 m3in the corridors and lobbies - 10 m3.
According to the general sanitary standards for residential premises, in one hour there is a full exchange of air mass in the amount of 30 m.3 per person - based on the number of tenants.
There is another approach to calculating the volume of air - by area. For every square meter of living space there are 3 m3.
We should also mention the ventilation of industrial facilities and storage sheds - 20 m.3 per unit area. In such huge rooms, ventilation systems are built on the basis of a multicomponent system of paired fans (4, 8, 16 and more pcs in the frame)
For the remaining outbuildings there are ready regulatory parameters. So, the kitchen with electric stove - more than 60 m3with a gas stove - more than 80 m3, bathroom - not less than 25 m3 etc.
In addition, it must be remembered that for living rooms the speed of the air flow is no more than 2 m / s, and for the kitchen and bathroom the speed should be 4-6 m / s.
Formulas and explanations for them
Go directly to the characteristics and formulas. Calculations occur in several stages, at each of which we calculate one of the characteristics of the ventilation system.
Working air volume
Consider the calculation of the working volume of air (m3/ h)
For the office, we recommend doing the calculation of the number of people:
V = 35 * N,
Where N - the number of people at the same time in the room.
For apartments and private houses it is necessary to make a calculation regarding the amount of living space:
V = 2 * S * H,
Where: 2 - coefficient of frequency of air exchange per unit of time (for 1 hour); S - living space; H - the height of the premises.
Calculation of the duct section
Section air duct for ventilation calculated in cm2. The main air ducts are of two types in cross section: round and rectangular.
The cross-sectional area of the pipe is calculated by the ratio:
Scut off= V * 2.8 / ω,
Where: Scut off - cross-sectional area; V - air volume (m3/ h); 2,8 - the coefficient of harmonization of dimensions; ω - flow rate in the highway (m / s).
The speed of air flow through the line is usually equivalent to 2-3 m / s.
By calculating the duct cross-sectional area, you can determine the diameter for a round or width / height for a rectangular duct. Knowing the width we can find the height of the section and vice versa. The diameter of the round section will be equal to √4 * Scut off/ pi
Number and size of diffusers
Consider next how to calculate the number and size of diffusers. The dimensions of the sprayer are usually chosen 1.5-2 times larger than the cross-sectional area of the main line.
With the number of diffusers a little more complicated, they are calculated by the formula:
N = V / (2820 * ω * d2),
Where: N - the required number of diffusers; V - air mass flow (m3/ h); ω - air flow rate (m / s); d - diameter of the diffuser (m), if it is round.
If the diffuser is rectangular, then:
N = π * V / (2820 * ω * 4 * a * b),
Where: π - Pi, a and b - dimensions of the section.
Installation Performance Parameters
There are two of the most important characteristics of the ventilation unit - power and the degree of generated pressure. The power of the ventilation station is calculated as follows:
P = ΔT * V * Cv / 1000,
Where: ΔT - Delta inlet / outlet air temperature (° С); V - air mass flow (m3/ h); Cv - air heat capacity (0.336 W * h / m³ * ° С).
The generated pressure is determined by the characteristic curve of the performance of the main fan.
This parameter should be equivalent to the aerodynamic resistance of the air network. Fan manufacturers provide a curve curve in the product data sheet.
In addition, it is important to have a general idea of the heater input air flow - the heater. This is a separate part of the ventilation system, where the air is heated. Passing, for example, through a heat radiator, the air is thereby heated.
An air heater in which heating takes place through a radiator and the exchange of thermal energy with the exhaust flow is called a recuperator. There are single and multi-section recuperators that allow air flow to be mixed with a large difference in their input temperatures.
In conclusion, it is worth mentioning the supply voltage for the ventilation unit. It is recommended to use a network of voltage 380 V, it will ensure reliable operation of the installation of any capacity.
The specifics of the installation of mechanical ventilation
With the installation of the ventilation unit of the inflow type, the home master could certainly cope without the involvement of the workers.
However, it is worth remembering that the work is carried out at a dangerous height for an inexperienced performer. Therefore, it is better to attract those who have the experience, tools and safety devices to perform the following steps:
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Stage 1: A diamond drilling rig designed to form holes in concrete, masonry, brick, drill a hole with a diameter equal to the duct section
Stage 2: The drilled hole is cleaned of dust and small particles of the drilled structure, then an air duct is brought into it
Stage 3: The installation case is separated from the system unit to facilitate the work
Stage 4: The system unit is temporarily removed to the side, the case is checked for the strength of the connections so that they do not have to be adjusted at height
Stage 5: The safety rope, to which the hull will be fixed, is led into the air duct and thrown into the window
Stage 7: The second part of the safety hull attached to the case is carried out in the duct from the street
Stage 7: Gently holding and securing the rope, the body is connected to the duct
Step 8: Carefully unwrap the case and direct it to the window, bring the system unit into the case and snap it
Drilling a hole in the wall for channel entry
Installing the duct in the hole
Branch of the casing of the air handling unit
Body preparation for installation work
Fixing a safety rope
Cable fastening for housing installation
Installation of the housing at the location
Attaching the system unit
Upon completion of the completely complicated installation manipulations of the directly inlet installation, all that remains is to connect it to the communications.
Let us consider this process in more detail with the help of the following photo collection.
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Step 9: To connect the air handling unit to the power supply, holes are again drilled in the wall, but already with a diameter equal to the diameter of the channel used in the gasket
Step 10: Separate lines are laid for connecting the power supply to the installation and for the control system
Step 11: On the side of the room, a bracket is connected to the duct to fix the noise absorbing device.
Step 12: A sound-absorbing diffuser, which is included in the equipment bundle, is screwed onto the bracket attached to the duct
Step 13: Install the system control panels inside the room in a convenient place to use. Installation is based on the principle of conventional sockets.
Step 14: After the installation and connection of the ventilation equipment is completed, it is checked for operability.
If the installation is planned to be used for servicing two adjacent rooms, an additional air duct is connected to it.
If located on a non-insulated loggia with natural air flow, an adapter is required. The scheme of its installation is shown in the figure. The flush sink itself is not warmed.
Drilling of cable holes
Power and Control Wiring
Mounting bracket for diffuser
Installing and fixing the diffuser
Installation of control panels
The appearance of the air handling unit
Wiring option for two rooms
Installation scheme on non-insulated loggia
Information about the sequence of installation of forced ventilation systems will help to avoid many of the worst mistakes made by inexperienced installers.
Features of the construction of natural PVV
When developing high-quality natural exhaust ventilation, most experts follow a certain “charter” of design and installation work.
These rules help create truly effective and economical solutions for even the most unusual arrangements of rooms and utility rooms. in a private house and multi-room apartment high-rise buildings.
During the design of ventilation, you should try to create a natural flow of air from the living rooms through the corridors to the bathroom and the kitchen.
Corridors in this case act as flow spaces. Therefore, the main ventilation unit of the system should be located in the center of the house, in the upper part of the corridors or outbuildings.
For example, the ventilation module for a 2-storey private house can be located on the ground floor at the top of the utility room or the main corridor. For a 1-storey building, as an option, in the lower part of the attic.
Laying the main pipeline, you need to remember that the supply air should go into the living rooms, and exhaust - to go through the kitchen and utility rooms.
Therefore, the supply diffusers are placed on the conditional boundary “room-environment”, and the exhaust in the kitchen, bathroom, utility room, toilet.
The diffuser combines two functions: a uniform distribution of fresh air and the removal of already used air. They come in all shapes. Made of thin sheet metal and plastic
There are comments on the height of the location of the entrance and exit air apertures. The exit of the ventilation system is placed necessarily above the roof level of the building.
This will protect UIP from the secondary intake of the newly extracted air through the exhaust holes.
Fresh air must be taken at a height of at least 2 meters from the ground.
Because small abrasive particles and dust can rise with the help of wind currents to a height of more than 1 meter and fly into the inlet diffusers, thereby quickly clog the filters of the primary cleaning.
Conclusions and useful video on the topic
The video tells and demonstrates the features of the design and installation of UIP in a private house:
Another illustrative example of a ready-made solution for ventilation of a private 1-storey wooden house:
Summarizing the above information, we note that the supply and exhaust ventilation is simple to design, available for purchase and installation of the system.
Ventilation in conjunction with the heating system allows you to organize the balance of fresh and warm air in the room.
You were engaged in arrangement of ventilation in the country? Or do you know the secrets of designing and installing a ventilation system in an apartment? Please share your experience - leave your comments on this article.
