Equipping housing with all the benefits of civilization is a necessity for any owner. Not to be included in the list engineering systems home ventilation and air conditioning. The arrangement of these complexes must be approached with the utmost 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 disturbed, 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. The oxygen consumption along the entire length is considered to be stable.
- Determination of the main line with the maximum air consumption. This will be the longest element of the circuit.
- Cross-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 gratings.
- All sections are marked from the least loaded in order of increasing pressure.
- Exhaust, installed on industrial, commercial, sports grounds and in residential buildings mounted both inside and outside the building.
- Supply air, supplying rooms of various types with prepared air.
- Combined with recovery unit.
- Provide the necessary heating of the mixture and the removal of excess heat at their economic expediency.
- The speed indicators of the movement of air flows should not violate the comfort of being in the premises.
- Limit concentration harmful substances, not exceeding the values determined by GOST 12.1.005–88.
- Metal (galvanized, stainless or black steel).
- Made of flexible film (plastic or aluminium).
- Hard plastic.
- Fabrics.
- Drawing up a plan indicating required amount supply or exhaust air. This is the baseline on which all design work is based.
- Marks on the diagram of individual sections with data on the amount of oxygen moving through them. It is necessary to specify gratings, cross-section differences, bends and valves.
- After selecting the maximum speed, the caliber, diameter or size of the sides of the channel is calculated.
- Branches are ordinary and S-shaped (ducks).
- Adapters in diameter and geometric shape.
- Tees.
- Umbrellas.
- Vent-Calc for calculating cross-sectional area, thrust and resistance in sections.
- GIDRV 3.093 provides control over the calculation of channel parameters.
- Ducter 2.5 selects system elements according to certain characteristics.
- CADvent based on AutoCAD with a maximum database of elements.
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Causes of ventilation problems
If the calculations are correct, then the clean air normal humidity, as well as removal unpleasant odors will be the maximum allowed. Otherwise, the formation of mold, fungus in bathrooms and toilets, constant stuffiness in kitchens and rooms is guaranteed. The situation is aggravated by the fact that almost all premises are equipped with airtight plastic windows without slot ventilation. We have to compensate for the lack of fresh air forcibly.
Another cause of problems with the elimination of waste masses, unpleasant odors and excess water vapor are blockages and depressurization of ventilation pipes. The redevelopment of premises can have a negative impact on the microclimate if you do not resort to engineering assistance when calculating the area of air ducts when upgrading ventilation in accordance with the new parameters.
The easiest way to fix problems in this system is to check for the presence of traction. To do this, bring a sheet of paper or a burning match to the exhaust channel. The use of open fire 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 supply and proceed to eliminate them, which may require re-calculating all parameters.
Air duct area
Grounds for determining areas
The ventilation communications system is complex design. When designing it, it is necessary to calculate the quadrature of rectangular and the cross section of round sections of the network, convert them to square meters. m, calculate the area of tie-ins, transitions. This can be done using special mathematical expressions. or a special program - an online calculator for calculating air ducts.
Formula calculation
There are several definitions for making calculations. The main ones are:
MagiCAD duct area
Sequence of operations
In order not to be mistaken in the projected indicators, it is necessary to break the entire work cycle into stages. Approximately the following sequence will turn out:
Given the preconditions, it is possible to calculate the performance of ventilation systems. The formulas to be used are:
It is assumed that special reference books will be used during the calculations. They indicate the practical losses due to friction, air consumption at various flow rates:
For extinguishing overpressure aperture is applied. The coefficient of its resistance is determined as follows:
Data from these tables is used for several types ventilation units. Among them:
Calculation of pressure drop in ducts
Calculation of the diameter of the channels
Having determined the speed of the air masses inside the route, we can proceed to the calculation of 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 cost of oxygen in m3/h, v is the speed of the air flow, 3600 is the time correction factor. Having learned it, the diameter is calculated:
Sizing main pipelines, some conditions must be met. The project must meet the following criteria:
Basic concepts of aerodynamic calculation LESSON 1 (total 10 lessons)
Channel types
Before you start calculating air ducts and fittings, you need to know what material they are made of. The recalculation of the cross-sectional area and the manner of movement of air masses inside depend on this. Channels for ventilation are:
Their shape is mainly rectangular or round, less often - oval. They are made on industrial enterprises, since it is quite difficult to organize production directly at the facility.
Diameter definition
This task becomes the main one when creating project documentation to the ventilation system. The process can be carried out both by specialist installers and independently, using the calculator of air ducts and fittings. This can be done in two ways.
The variant with the use of allowable speeds is based on the normalized speed of movement inside the pipe. The indicators are selected for a particular type of premises and a section of the highway according to the recommended values.
Each building is characterized by the maximum permitted rate of air distribution, which is unacceptable to exceed. For regular use, you should take this scheme:
Simple calculation of ventilation with a heat exchanger.
And also you can select these parameters according to the method of determining pressure losses, summing them up on indirect sections and bends, gratings and tees. This will require geometric formulas and special tables.
Material selection
This procedure is performed at the facility that manufactures the duct and accessories. In this case, the quantity of raw materials for the production of the required quantity of products is determined. For such purposes, a profile development 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. You have to produce for each element separately. It is not possible to carry out the operation on site, therefore all additional parts are supplied by the manufacturer together with the main structural elements.
The most common components for ventilation and air conditioning systems are:
For any of these components, special role in the complex of the ventilation system, so each of them is designed separately. It is not difficult to calculate both shaped products and the area of air ducts with an online calculator.
Assistance Programs
To eliminate human factors in the calculations, as well as reduce the design time, several products have been developed that allow you to correctly determine the parameters of the 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 will 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 fixtures.
The task of organized air exchange in the rooms of a residential building or apartment is to remove excess moisture and exhaust gases, replacing them with fresh air. Accordingly, for the exhaust and inflow device, it is necessary to determine the amount of air masses to be removed - to calculate the ventilation separately for each room. Calculation methods and air flow rates are accepted exclusively according to SNiP.
Sanitary requirements of regulatory documents
The minimum amount of air supplied to and removed from the cottage rooms by the ventilation system is regulated by two main documents:
- "Residential multi-apartment buildings" - SNiP 31-01-2003, paragraph 9.
- "Heating, ventilation and air conditioning" - SP 60.13330.2012, mandatory Appendix "K".
The first document sets out the sanitary and hygienic requirements for air exchange in residential premises apartment buildings. On these data, the calculation of ventilation should be based. 2 types of dimensions are used - air mass flow rate by volume per unit of time (m³ / h) and hourly multiplicity.
Ventilation is a primitive way to renew oxygen in a home.Reference. The air exchange rate is expressed as a figure indicating how many times within 1 hour the air environment of the room is completely updated.
Depending on the purpose of the room, supply and exhaust ventilation should provide the following flow rate or the number of updates of the air mixture (multiplicity):
- living room, nursery, bedroom - 1 time per hour;
- kitchen with electric stove– 60 m³/h;
- bathroom, bathroom, toilet - 25 m³ / h;
- for and kitchen with gas stove a multiplicity of 1 plus 100 m³/h is required during the operation of the equipment;
- , burning natural gas - three times the renewal plus the volume of air required for combustion;
- pantry, closet, etc. utility rooms– multiplicity 0.2;
- drying or laundry room - 90 m³ / h;
- library, office - 0.5 times per hour.
Note. SNiP provides for a reduction in the load on general ventilation when the equipment is not working or there are no people. In residential premises, the multiplicity decreases to 0.2, technical - to 0.5. The requirement for rooms where gas-using installations are located remains unchanged - an hourly one-time renewal of the air environment.
The emission of harmful gases due to natural draft is the cheapest and easiest way to renew the air Clause 9 of the document implies that the volume of the extract is equal to the amount of inflow. The requirements of SP 60.13330.2012 are somewhat simpler and depend on the number of people in the room for 2 hours or more:
- If 1 resident has 20 m² or more of the area of the apartment, a fresh influx of 30 m³ / h per 1 person is provided to the rooms.
- The volume of supply air is calculated by area when there are less than 20 squares per 1 tenant. The ratio is as follows: 3 m³ of inflow is supplied per 1 m² of housing.
- If the apartment does not provide ventilation (there are no vents and windows that open), 60 m³ / h of a clean mixture must be applied to each resident, regardless of the quadrature.
The listed normative requirements of two different documents do not contradict each other at all. Initially, the performance of the ventilation general exchange system is calculated according to SNiP 31-01-2003 "Residential buildings".
The results are checked against the requirements of the Code of Rules "Ventilation and Air Conditioning" and, if necessary, corrected. Below we will analyze the calculation algorithm using an example one-story house shown in the drawing.
Determination of air consumption by multiplicity
This typical calculation of supply and exhaust ventilation is performed separately for each room of an apartment or a country cottage. To find out the flow of air masses in the building as a whole, the results obtained are summarized. A fairly simple formula is used:
Explanation of designations:
- L is the desired volume of supply and exhaust air, m³/h;
- S is the quadrature of the room where ventilation is calculated, m²;
- h - ceiling height, m;
- n is the number of room air updates within 1 hour (regulated by SNiP).
Calculation example. The area of the living room of a one-story building with a ceiling height of 3 m is 15.75 m². According to the requirements of SNiP 31-01-2003, the multiplicity n for residential premises is equal to one. Then the hourly flow rate of the air mixture will be L = 15.75 x 3 x 1 = 47.25 m³/h.
An important point. Determination of the volume of air mixture removed from the kitchen with a gas stove depends on the installed ventilation equipment. A common scheme looks like this: a single exchange according to the standards is provided by the system natural ventilation, and an additional 100 m³ / h is emitted by household.
Similar calculations are made for all other rooms, a scheme for organizing air exchange (natural or forced) is developed and the dimensions of the ventilation ducts are determined (see the example below). A calculation program will help automate and speed up the process.
Online calculator to help
The program calculates the required amount of air according to the multiplicity regulated by SNiP. Just select the type of room and enter its dimensions.
If ventilation in a house or apartment does not cope with its tasks, then this is fraught with very serious consequences. Yes, problems in the operation of this system do not appear as quickly and sensitively as, say, problems with heating, and not all owners pay adequate attention to them. But the results can be very sad. This is stale waterlogged indoor air, that is, an ideal environment for the development of pathogens. These are misted windows and damp walls, on which mold foci may soon appear. Finally, this is simply a decrease in comfort due to smells spreading from the bathroom, bathroom, kitchen into the living area.
In order to avoid stagnation, air must be exchanged with a certain frequency in the premises for a period of time. The inflow is carried out through the living area of the apartment or house, the hood - through the kitchen, bathroom, bathroom. It is for this that windows (vents) of exhaust ventilation ducts are located there. Often, homeowners who are starting repairs ask if these vents can be repaired or reduced in size in order, for example, to install certain pieces of furniture on the walls. So - it is definitely impossible to completely block them, but transfer or change in size is possible, but not only on the condition that the necessary performance will be ensured, that is, the ability to pass the required volume of air. And how to define it? We hope that the proposed calculators for calculating the cross-sectional area of the ventilation vent will help the reader.
Calculators will be accompanied by the necessary explanations for the calculations.
Calculation of normal air exchange for effective ventilation of an apartment or house
So, during normal operation of ventilation for an hour, the air in the premises must constantly change. Operating guidance documents(SNiP and SanPiN) set the norms for the flow of fresh air into each of the premises of the residential area of the apartment, as well as the minimum volume of its exhaust through the channels located in the kitchen, in the bathroom in the bathroom, and sometimes in some other special rooms.
| Room type | Minimum air exchange rates (multiplicity per hour or cubic meters per hour) | |
|---|---|---|
| INFLOW | HOOD | |
| Requirements under the Code of Rules SP 55.13330.2011 to SNiP 31-02-2001 "Single-apartment residential buildings" | ||
| Residential premises with permanent residence of people | At least one volume exchange per hour | - |
| Kitchen | - | 60 m³/hour |
| Bathroom, toilet | - | 25 m³/hour |
| Other premises | Not less than 0.2 volume per hour | |
| Requirements according to the Code of Rules SP 60.13330.2012 to SNiP 41-01-2003 "Heating, ventilation and air conditioning" | ||
| Minimum outdoor air consumption per person: living quarters with permanent residence of people, in conditions of natural ventilation: | ||
| With a total living area of more than 20 m² per person | 30 m³/h, but at the same time not less than 0.35 of the total air exchange volume of the apartment per hour | |
| With a total living area of less than 20 m² per person | 3 m³/hour for every 1 m² of room area | |
| Requirements according to the Code of Rules SP 54.13330.2011 to SNiP 31-01-2003 "Residential multi-apartment buildings"
|
||
| Bedroom, nursery, living room | One volume exchange per hour | |
| Cabinet, library | 0.5 volume per hour | |
| Linen, pantry, dressing room | 0.2 volume per hour | |
| Home gym, billiard room | 80 m³/hour | |
| Kitchen with electric stove | 60 m³/hour | |
| Premises with gas equipment | Single exchange + 100 m³/h for a gas stove | |
| A room with a solid fuel boiler or stove | Single exchange + 100 m³/h per boiler or furnace | |
| Home laundry, dryer, ironing | 90 m³/hour | |
| Shower, bath, toilet or shared bathroom | 25 m³/hour | |
| home sauna | 10 m³/h per person | |
An inquisitive reader will surely notice that the standards for different documents are somewhat different. Moreover, in one case, the norms are set exclusively by the size (volume) of the room, and in the other - by the number of people permanently staying in this room. (Under the concept of permanent residence is meant being in the room for 2 hours or more).
Therefore, when carrying out calculations, it is desirable to calculate the minimum volume of air exchange according to all available standards. And then - choose the result with the maximum indicator - then there will definitely be no error.
The first proposed calculator will help you quickly and accurately calculate the air flow for all rooms of an apartment or house.
Calculator for calculating the required volume of air inflow for normal ventilation
Industrial ventilation is designed taking into account several facts, the cross-section of air ducts has a significant effect on everything.
- Air exchange rate. During the calculations, the features of the technology are taken into account, chemical composition emitted harmful compounds, and the dimensions of the room.
- Noise. Ventilation systems should not worsen working conditions in terms of noise. The cross section and thickness are selected in such a way as to minimize the noise of air flows.
- Efficiency common system ventilation. Several rooms can be connected to one main air duct. Each of them must maintain its own ventilation parameters, and this largely depends on the correct choice of diameters. They are selected in such a way that the dimensions and capabilities of one common fan can provide regulated system modes.
- Profitability. The smaller the energy losses in the ducts, the lower the consumption electrical energy. At the same time, it is necessary to take into account the cost of equipment, to choose economically justified dimensions of the elements.
Efficient and economical system ventilation requires complex preliminary calculations, only specialists with higher education can do this. Currently, plastic air ducts are most often used for industrial ventilation, they meet all modern requirements, make it possible to reduce not only the dimensions and cost of the ventilation system, but also the cost of its maintenance.
Calculation of the diameter of the air duct
To calculate the dimensions, you need to have the initial data: the maximum allowable speed of the air flow and the volume of air passed per unit of time. This data is taken from specifications ventilation system. The speed of air movement affects the noise of the system, and it is strictly controlled by sanitary state organizations. The volume of air to be passed must correspond to the parameters of the fans and the required exchange rate. The calculated air duct area is determined by the formula Sc = L × 2.778 / V, where:
Sc - cross-sectional area of the duct in square centimeters; L - maximum supply (flow) of air in m 3 / hour;
V is the estimated operating airflow speed in meters per second without peaks;
2.778 is a coefficient for converting various metric numbers to diameter values in square centimeters.
Designers of ventilation systems take into account the following important dependencies:
- If it is necessary to supply the same volume of air, reducing the diameter of the air ducts leads to an increase in the air flow rate. This phenomenon has three negative consequences. First, an increase in air speed increases noise, and this parameter is controlled by sanitary standards and cannot exceed permissible values. Secondly, the higher the air speed, the higher the energy loss, the more powerful the fans are needed to ensure the specified modes of operation of the system, the larger their size. Thirdly, the small dimensions of the air ducts are not able to properly distribute flows between different rooms.
- An unjustified increase in the diameter of the air ducts increases the price of the ventilation system, creates difficulties during installation work. Large sizes render Negative influence on the cost of system maintenance and the cost of manufactured products.
The smaller the diameter of the air duct, the faster the speed of air movement. And this not only increases noise and vibration, but also increases the resistance of the air flow. Accordingly, to ensure the required calculated exchange rate, it is required to set powerful fans, which increases their size and is economically unprofitable at current prices for electrical energy.
With an increase in diameters, the above problems disappear, but new ones appear - the complexity of installation and the high cost of overall equipment, including various shut-off and control valves. In addition, air ducts large diameter require a lot of free space for installation, under them you have to make holes in the main walls and partitions. Another problem is that if they are used for space heating, then big sizes air ducts require increased costs for thermal protection measures, which additionally increases the estimated cost of the system.
In simplified versions of calculations, it is taken into account that the optimal speed of air flows should be in the range of 12–15 m/s, due to this, it is possible to somewhat reduce their diameter and thickness. Due to the fact that the main air ducts in most cases are laid in special technical channels, the noise level can be neglected. In the branches that enter directly into the premises, the air speed decreases to 5–6 m/s, thereby reducing noise. The air volume is taken from the SaNiPin tables for each room, depending on its purpose of dimensions.
Problems arise with main ducts of considerable length in large enterprises or in systems with many branches. For example, with a normalized air flow of 35,000 m 3 / h and an air flow rate of 8 m / s, the diameter of the air duct must be at least 1.5 m with a thickness of more than two millimeters, with an increase in air flow speed to 13 m / s, the dimensions of the air ducts are reduced to 1 m.
Pressure loss table
The diameter of the branches of the air ducts is calculated taking into account the requirements for each room. It is allowed to use the same dimensions for them, and to change the air parameters, install different adjustable throttle valves. Such options for ventilation systems allow you to automatically change performance indicators, taking into account the actual situation. There should be no drafts in the rooms caused by ventilation. Creating a favorable microclimate is achieved through right choice places of installation of ventilation grilles and their linear dimensions.
The systems themselves are calculated using the constant velocity method and the pressure loss method. Based on these data, the dimensions, type and power of fans are selected, their number is calculated, installation sites are planned, and the dimensions of the air duct are determined.
The calculation of the area of air ducts and fittings is made before the installation of ventilation communications. The efficiency of the entire ventilation system depends on the correct implementation of them. In practice, experienced craftsmen use two main measurement methods: using a formula and using an online calculator. Calculation of the area of air ducts and fittings is a time-consuming and responsible task. The editors of the online magazine Homius.ru have prepared a review on this topic especially for their readers, using all modern possibilities and knowledge experienced craftsmen. In this article you will find useful advice for calculating data, as well as a convenient online calculator.
There may be an error in area calculations using formulas.
1 Why do we need to calculate the area of the duct and fittings
2 What data is needed to calculate the parameters of the duct
4 Calculation of the area of duct fittings
4.1 What programs exist for finding the parameters of duct fittings
5 Calculation square meters(cross-sectional area) of the duct
5.1 Calculator for calculating the required duct diameter
6 Calculation of the air velocity in the duct
7 Calculation of the resistance of the duct network
8 Pressure loss in straight sections
9 Pressure losses due to local resistances
10 Calculation of materials for duct and fittings
11 Calculation of heater power in the network
12 Conclusion
Why do we need to calculate the area of the duct and fittings
The ventilation complex consists of different elements. In order to correctly select all the details, it is necessary to calculate their area, which is affected by the following parameters:
volume and speed of air masses;
tightness of connections;
noise during operation of the ventilation system;
electricity consumption.
It is important! Thanks to correctly performed calculations, it is possible to determine the optimal number of fittings for organizing a ventilation system for a particular room. This will prevent unnecessary spending on the purchase of elements that will not fit later.
Variety of duct designs and materials
What data is needed to calculate the parameters of the duct
To calculate the duct, you must first determine two indicators:
the norms established for the supply of fresh flows per 1 m² of the room per hour or the frequency of air exchange, information is taken from regulatory sources. Based on these data, knowing the volume of the room, you can easily determine the value of the ventilation system performance. Accordingly, the volume of air is calculated by multiplying the multiplicity by the volume of the room;
By sanitary standards. In this case, 60 m³ should be taken for each person permanently in the room, 20 m³ for a temporarily staying person.
The effectiveness of industrial air purification depends on correct calculations
The main task of the ventilation system is to improve the microclimate in the room and purify the air masses by removing the exhaust air to the outside. For high-quality performance, first of all, it is necessary to carry out design work and calculate the quadrature of the air ducts. During planning, the shape of the pipes, the number of elements required to connect the sections, and the size of the section will also be determined.
Calculations can be done in two ways:
independently using formulas;
using an online calculator.
The first case is the most difficult option, it is important to understand all the values that are used in the calculations. For an online calculator, it is enough to enter the initial data, the software package will independently perform all the calculations. One of the main parameters for designing an air duct and fittings is its design. You can choose pipes of rectangular or round cross-section. The throughput of round products is much higher than that of rectangular ones.
Maximum accuracy in calculations
the least amount of air masses moved;
air transport speed.
And also a few more parameters directly depend on the size of the section:
the larger the cross section, the less noise the flows move;
consequently, the cost of electricity is reduced.
On the other hand, such a system will require more material, respectively, and the cost will be much higher. Thanks to the calculation formula, you can determine the actual cross-sectional area of the duct:
S \u003d A × B / 100, where A and B are, respectively, the height and width of the section.
The rectangular air duct is almost invisible above the furniture
The duct with a cross section in the form of a circle does not cause difficulties during installation and has an excellent air flow capacity, since internal resistance is minimized. The choice of the form of communications follows from the personal preferences of consumers and the external design of the premises.
The actual area is calculated as follows:
S = π × D²/400, where:
π is a constant equal to 3.14;
D - element length.
Special methods have been developed, for example, SNiPs, in which the calculated actual areas are compared with the required indicators. They make it easy to choose optimal size communications.
When making calculations, the following factors must be taken into account:
the cross-sectional area for straight sections of the duct should be calculated separately;
be sure to take into account the resistance that will be exerted on the air masses during their transportation;
design should start from the central highway.
If the air flow rate exceeds the required values, and this directly affects the noise during operation, it is necessary to additionally purchase special silencers or increase the cross section of the flange element of the central channel.
Circular area product
Calculation of the area of duct fittings
It will be difficult for a person who is not connected with mathematical formulas to perform the calculations correctly, an error in one indicator will affect the performance of the ventilation system, respectively, and the quality of air purification.
To simplify the process of calculating the surface area of the duct, you can use an online calculator and special programs that perform all the algorithms, for this you only need to enter the primary indicators.
The program for counting and selecting elements
What programs exist for finding the parameters of duct fittings
To help engineers, to eliminate errors associated with the human factor, as well as to speed up the process, special programs were created that can not only perform accurate calculations, but also 3D modeling of the future structure.
Program
Short description
The program calculates the cross-sectional area, thrust, resistance on different segments.
GIDRV 3.093 The program will perform a new and check calculation of the duct data.
Ducter 2.5 In the program, you can select the elements of the ventilation system, calculate the cross-sectional areas of the structure.
This complex was created on the basis of AutoCAD, has the most detailed library of elements and features.
Software calculation and design of ventilation
Calculation of square meters (sectional area) of the duct
The size of the ventilation pipe is influenced by many factors: flow rate, pressure on the walls, air volume. If you perform calculations with an error, for example, reduce the cross section of the main network, the speed of air masses will increase, noise will appear, pressure and electricity consumption will increase.
The calculation of the cross-sectional area of the duct is calculated using the following formula:
S = L × κ / ω, where:
L - air consumption, m³/h;
ω - speed of air flow, m/s;
κ - design coefficient equal to 2.778.
Calculator for calculating the required duct diameter
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Calculation of air velocity in a duct
When calculating the ventilation system, one of the main indicators is the frequency of air exchange. In other words, how much air mass is necessary for comfortable ventilation of 1 m³ of a room in 1 hour. In this case, you can also refer to the development tables, but you should be aware that all the indicators in them are rounded, so more accurate data is obtained with independent calculations. The air exchange rate can be calculated using the formula:
N \u003d V / W, where V is the amount of fresh air masses that enter the room in 60 minutes (m³ / hour);
W is the volume of the room, m³.
You can carry out aerodynamic calculations and calculate the speed of air movement using the following formula:
ω = L / 3600 × S, where L is the volume of air used in 1 hour;
S - cross-sectional area of the duct.
Air exchange rates for an apartment
Calculation of the resistance of the duct network
Air flows during transportation through pipes experience resistance, especially for pipes with a cross section in the form of a rectangle. To ensure the normal performance of the system, it is necessary to select a fan of the appropriate capacity. It is difficult to manually determine these parameters on your own, in project team All calculations are performed using the program.
The resistance is not affected by the number of rooms served by the ventilation system, the value of the coefficient depends on the structure and length of the communication.
Flow rate in direct relation to resistance
Pressure loss in straight sections
To calculate the performance of ventilation equipment, you can simply add up the required amount of air masses and choose a model that fits these parameters. However, the product data sheet does not take into account the air duct network. Therefore, when it is connected to the system, the performance will drop significantly depending on the resistance parameter in the pipeline. To determine the pressure drop in the system, it is necessary to clarify its decrease in flat areas, turning and connecting elements. The pressure drop in flat areas is determined by the formula:
P \u003d R × L + Еi × V2 × Y / 2, where R - specific loss pressure caused by friction force during air movement, Pa/m;
L is the length of the straight section of the duct, m;
ω – air velocity, m/s Y – air mass density, kg/m³;
Ei - the sum of the pressure losses due to local resistances (bends, transitions, gratings, etc.), the data can be taken from the reference book.
Rectilinear section of ventilation
Pressure loss at local resistances
To calculate the losses on the rotary elements, it is necessary first of all to determine all the sections that will interfere direct traffic streams. You can use a formula, but all data, depending on the duct element and material of manufacture, has already been determined and is background information. So, gradually section by section should be passed along its entire length, then add up all the indicators. We must not forget about the segment that is located behind the fan, because there should also be enough pressure to drain the flows.
During the calculation, all curvilinear connections must be taken into account
Calculation of materials for the duct and fittings
To select the dimensions and structural elements, for example, tees, bends, reducers, there is no need to do it manually, especially since the range is quite large. Everything can be done in a special program, including the area of shaped parts of air ducts, for this you just need to enter the primary data. The result will be ready in a few seconds. And also, if necessary, you can use the tabular form of equivalent cross-sections of circular diameter air ducts, in which the reduction in friction pressure is equal to the pressure reduction in rectangular sections.
The calculation of materials was carried out using the program
Calculation of heater power in the network
To calculate the supply ventilation system, it is necessary first of all to take into account the power of the heater that heats the incoming masses in the cool season. According to the approved standards, the temperature of the flow that enters the room must be at least 18 ° C, the outdoor air indicators depend on the location of the region. IN modern equipment it is possible to regulate the speed of circulation of air masses, thus, you can save in winter time electricity. Before choosing a model, the heating temperature of the air that enters from the outside is calculated by the formula:
ΔT \u003d 2.98 × P / L, where P is the power of the equipment, W;
L - air mass consumption.
Proper calculations are the key to many years of equipment operation.
Conclusion
If necessary, you can understand all the calculations, however, with the help of the program, the possibility of an error is excluded, which during operation will be quite expensive. It is enough to enter the primary parameters into the program and analyze the obtained indicators in a fraction of a second. You can also seek engineering assistance in calculating the area of air ducts in professional design workshops.
We tried to describe in as much detail as possible the entire process of self-calculation, and also talked about software products. In the comments, you can clarify incomprehensible points, the team of our magazine will be happy to answer them.
The principle of operation of ventilation can be found on the video
