Let's start, perhaps, with natural and. As the name implies, the first type includes ventilation and everything that has nothing to do with devices. Accordingly, mechanical ventilation includes fans, hoods, supply valves and other equipment for creating forced air flow.
Good for the moderate speed of this flow, which creates comfortable conditions indoors for a person – the wind is not felt. Although correctly installed high-quality forced ventilation also does not bring drafts. But there is also a minus: at low air flow speed at natural ventilation a wider cross-section is needed to feed it. As a rule, the most effective ventilation is provided with complete open windows or doors, which speeds up the air exchange process, but can negatively affect the health of residents, especially in winter period year. If we ventilate the house by partially opening the windows or completely opening the vents, such ventilation requires about 30–75 minutes, and here the window frame may freeze, which may well lead to condensation, and cold air, taken over a long period of time, leads to health problems. Widely open windows speed up air exchange in the room; through ventilation will take approximately 4–10 minutes, which is safe for window frames, but with such ventilation, almost all the heat in the house goes outside, and for a long time the temperature inside the premises is quite low, which again increases the risk of disease.
We should also not forget about the increasingly popular supply valves, which are installed not only on windows, but also on walls inside rooms (wall supply valve), if the window design does not provide for such valves. The wall valve provides air infiltration and is an oblong pipe installed through the wall, closed on both sides with grilles and adjustable from the inside. It can be either completely open or completely closed. For convenience in the interior, it is recommended to place such a valve next to the window, since it can be hidden under tulle, and the flow of passing air will be heated by radiators located under the window sills.
For normal air circulation throughout the apartment, it is necessary to ensure its free movement. To do this on interior doors install transfer grilles so that the air moves smoothly from supply systems to the exhaust, passing throughout the house, through all the rooms. It is important to consider that the correct flow is considered to be the one in which the smelliest room (toilet, bathroom, kitchen) is the last. If it is not possible to install an overflow grille, it is enough to simply leave a gap between the door and the floor, about 2 cm. This is enough for the air to move easily around the house.
In cases where natural ventilation is not enough or there is no desire to provide it, they switch to using mechanical ventilation.
Do you dream of having a healthy microclimate in your home and not a single room smelling musty and damp? In order for the house to be truly comfortable, it is necessary to carry out proper calculations of ventilation even at the design stage.
If you miss this during the construction of a house important point, in the future you will have to solve a whole range of problems: from removing mold in the bathroom to new renovations and installation of an air duct system. Agree, it’s not very pleasant to see breeding grounds for black mold in the kitchen on the window sill or in the corners of the children’s room, and to plunge into renovation work all over again.
The article we presented contains useful materials on the calculation of ventilation systems and reference tables. The formulas are given, visual illustrations And real example for premises of various purposes and a certain area, demonstrated in the video.
With correct calculations and proper installation, the ventilation of the house is carried out in a suitable mode. This means that the air in residential areas will be fresh, with normal humidity and without unpleasant odors.
If the opposite picture is observed, for example, constant stuffiness in the bathroom or other negative phenomena, then you need to check the condition ventilation system.
Image gallery
Conclusions and useful video on the topic
Video #1. Useful information on the principles of operation of the ventilation system:
Video #2. Along with the exhaust air, heat also leaves the home. Calculations of heat losses associated with the operation of the ventilation system are clearly demonstrated here:
Correct calculation of ventilation is the basis for its successful functioning and the key to a favorable microclimate in a house or apartment. Knowledge of the basic parameters on which such calculations are based will allow not only to correctly design the ventilation system during construction, but also to adjust its condition if circumstances change.
Many inexperienced owners of houses or apartments underestimate the importance of ventilation, and thus make an extremely serious mistake. Insufficient or improper organization of air exchange is stagnation with a sharp deterioration of the indoor microclimate, high humidity, the development of pathogenic microflora, which ultimately leads, at best, to rapid damage to the decoration and property in the apartment, and in the future to persistent health disorders, often turning into dangerous forms.
No matter how the ventilation of a house or apartment is organized, it must comply with certain standards. And one of the key indicators is volume fresh air, entering the premises within an hour. All other calculations of natural, supply, exhaust or combined ventilation in one way or another will be based precisely on the standards of air supply to residential premises. It’s easy to find the corresponding tables with standards on the Internet, but it’s even easier to use a special calculator for calculating supply ventilation standards.
The reader will find some explanations on the calculations below.
Equipping your home with all the benefits of civilization is a necessity for any owner. Can't help but be included in the list engineering systems home ventilation and air conditioning. The arrangement of these complexes must be approached with maximum responsibility, which is impossible without calculating the area of air ducts and shaped products. At the slightest mistake, the microclimate in the room will be disrupted, which will affect the comfort of all family members.
- Calculation of individual zones limited by tees or dampers. If there are branches, then they are added to this segment. Oxygen consumption along the entire length is considered stable.
- Determination of the main line with maximum air flow. This will be the longest element of the circuit.
- Sections on the calculated sections are selected in accordance with the recommendations of the state standard - ≤ 8 m/s in mains, ≤ 8 m/s in branches, ≤ 3 m/s in blinds and grilles.
- All areas are marked from the least loaded in order of increasing pressure.
- Exhaust systems installed in industrial, commercial, sports grounds and in residential buildings, mounted both inside and outside the building.
- Supply units supplying rooms of various types with prepared air.
- Combined with a recovery unit.
- Provide necessary heating mixtures and removal of excess heat when economically feasible.
- The speed of movement of air flows should not interfere with the comfort of being in the premises.
- Limit concentration harmful substances, not exceeding the values defined by GOST 12.1.005–88.
- Metal (galvanized, stainless or black steel).
- Made of flexible film (plastic or aluminum).
- Hard plastic.
- Fabrics.
- Drawing up a plan indicating required quantity supply or exhaust air. This is the basic indicator on which all design work is based.
- Markings on the diagram individual areas with data on the amount of oxygen moving through them. It is necessary to indicate the grilles, cross-sectional differences, bends and valves.
- After selection maximum speed the caliber, diameter or size of the sides of the channel is calculated.
- Bends are regular and S-shaped (canards).
- Adapters according to diameter and geometric shape.
- Tees.
- Umbrellas.
- Vent-Calc for calculating cross-sectional area, thrust and resistance of sections.
- GIDRV 3.093 provides control over the calculation of channel parameters.
- Ducter 2.5 selects system elements according to certain characteristics.
- CADvent, created on the basis of AutoCAD with a maximum database of elements.
Show all
Causes of ventilation problems
If the calculations are made correctly, then the supply of clean air of normal humidity, as well as the removal of unpleasant odors, will be the maximum permissible. Otherwise, the formation of mold and mildew in bathrooms and toilets, and constant stuffiness in kitchens and rooms are guaranteed. The situation is aggravated by the fact that almost all premises are equipped with sealed plastic windows without slot ventilation. We have to compensate for the lack of fresh air by force.
Another reason for problems with the elimination of waste materials, unpleasant odors and excess water vapor is blockages and depressurization of ventilation pipes. Negative influence The microclimate can be affected by the redevelopment of premises if you do not resort to engineering assistance in calculating the area of air ducts when modernizing ventilation in accordance with new parameters.
The easiest way to fix problems in this system is to check the presence of traction. To do this, you need to bring a sheet of paper or a burning match to the exhaust duct. The use of open flames in rooms with gas heating equipment is not recommended. If the deviation is clearly noticeable, then there is no need to talk about problems. If the result is the opposite, you should find out the reasons for the lack of fresh air flow and begin to eliminate them, which may require recalculating all the parameters.
Air duct area
Basis for determining areas
The ventilation communications system is complex design. When designing it, it is necessary to calculate the quadrature of the rectangular and the cross-section of the circular sections of the network, convert them into square meters. m, calculate the area of insets and transitions. This can be done using special mathematical expressions or a special program - an online calculator for calculating air ducts.
Calculation using formulas
There are several definitions for making calculations. The main ones are:
Air duct area MagiCAD
Sequence of operations
In order not to make mistakes in the projected indicators, you need to break the entire work cycle into stages. The sequence will roughly look like this:
Considering preconditions, you can calculate the performance of ventilation systems. The formulas to use are:
It is assumed that special reference books will be used during calculations. They indicate practical losses due to friction, air flow at various flow rates:
A diaphragm is used to dampen excess pressure. Its resistance coefficient is determined as follows:
The data from these tables is used for several types of ventilation units. Among them:
Calculation of pressure drop in air ducts
Calculation of channel diameter
Having determined the speed of movement of air masses inside the route, you can proceed to calculating the next parameter. It is determined by the formula S=R\3600v, where S is the cross-sectional area of the line, R is the oxygen consumption in m3/hour, v is the air flow speed, 3600 is the time correction factor. Having recognized it, the diameter is calculated:
When determining the size of main pipelines, certain conditions must be met. The project must meet the following criteria:
Basic concepts of aerodynamic calculation LESSON 1 (10 lessons in total)
Channel types
Before you start calculating air ducts and fittings, you need to know what material they are made of. The recalculation of the diameter area and the manner of movement of air masses inside depend on this. Ventilation channels are:
Their shape is mostly rectangular or round, less often oval. They are manufactured at industrial enterprises, since organizing production directly on site is quite difficult.
Determination of diameter
This task becomes the main one when creating design documentation for the ventilation system. The process can be carried out either by specialist installers or independently, using a calculator of air ducts and fittings. There are two ways to do this.
The option using permissible speeds is based on the normalized speed of movement inside the pipe. Indicators are selected for a specific type of premises and section of the highway according to recommended values.
Each building is characterized by the maximum permitted rate of air spread, which must not be exceeded. For regular use, you should take the following scheme:
Simple calculation of ventilation with a recuperator.
You can also select these parameters using the method of determining pressure losses, summing them up in indirect sections and bends, gratings and tees. This will require geometric formulas and special tables.
Material selection
This procedure is performed at the facility where the duct and accessories are manufactured. In this case, the amount of raw materials to produce the required amount of products is determined. For such purposes, a profile scan is created and formulas from geometry are used. For round sections this will be the diameter of the pipe multiplied by the circumference.
Shaped products are more difficult to calculate, since there are no ready-made formulas for them. It is necessary to produce for each element separately. It is not possible to carry out the operation on site, so all additional parts are supplied by the manufacturer along with the main structural elements.
The most common components for ventilation and air conditioning systems are:
Each of these components has a special role in the ventilation system complex, so each of them is designed separately. It is not difficult to calculate both shaped products and the area of air ducts using an online calculator.
Programs for assistance
To eliminate human factors in calculations, as well as reduce design time, several products have been developed that allow you to correctly determine the parameters of a future ventilation system. In addition, some of them allow the construction of a 3D model of the complex being created. Among them are the following developments:
Everyone solves the problem of selecting the dimensions of future ventilation independently. For an inexperienced installer, it would be preferable to design and install all components with the help of specialists who have experience in creating such highways and the appropriate equipment and accessories.
The cross-section of a rectangular and/or round air duct is calculated using two known parameters: air exchange by room and flow rate air.
Air exchange throughout the room can be replaced by fan performance. Supply air or exhaust fans indicated by the manufacturer in the product data sheet. When designing or pre-design development, air exchange is calculated based on the multiplicity. Multiplicity (the number of times the full volume of air in a room is replaced in 1 hour) is a coefficient from regulatory documentation.
The duct flow velocity must be measured if it is . And if the project is under development, then the flow rate in the air duct is set independently. The flow speed in the air duct should not exceed 10 m/s.
Below are formulas and a calculator based on them, with which you can calculate the cross-section of rectangular and round air ducts.
Formula for calculating the circular cross-section (diameter) of an air duct
Formula for calculating the rectangular cross-section of an air duct
Calculator for calculating the cross-sections of rectangular and round air ducts using air exchange and flow rate
Enter parameters in the fields air exchange and required flow rate in the air duct