Calculation of the area of ​​air ducts and fittings. How to calculate the cross section and diameter of the duct? Calculation of the cross-sectional area of ​​​​the ventilation duct

In order for the ventilation system in the house to work efficiently, it is necessary to make calculations during its design. This will not only allow you to use the equipment with optimal power, but also save on the system, fully preserving all the required parameters. It is carried out according to certain parameters, while completely different formulas are used for natural and forced systems. Separate attention should be paid to the fact that a forced system is not always required. For example, for a city apartment, natural air exchange is quite enough, but subject to certain requirements and norms.

Calculation of the size of the ducts

To calculate the ventilation of a room, it is necessary to determine what the cross section of the pipe will be, the volume of air passing through the ducts, and the flow rate. Such calculations are important, since the slightest errors lead to poor air exchange, noise of the entire air conditioning system, or large cost overruns during installation, electricity for the operation of equipment that provides for ventilation.

To calculate the ventilation for a room, find out the area of ​​​​the air duct, you must use the following formula:

Sc = L * 2.778 / V, where:

• Sc is the estimated area of ​​the channel;
• L is the value of the air flow passing through the channel;
• V is the value of the air velocity passing through the air duct;
• 2.778 is a special coefficient that is needed to match the dimensions - these are hours and seconds, meters and centimeters, used when including data in the formula.

To find out what the actual area of ​​the duct pipe will be, you need to use a formula based on the type of duct. For a round pipe, the formula applies: S = π * D² / 400, where:

• S is the number for the actual cross-sectional area;
• D is the number for the channel diameter;
• π is a constant equal to 3.14.

For rectangular pipes, you will need the formula S = A * B / 100, where:

• S is the value for the actual cross-sectional area:
• A, B is the length of the sides of the rectangle.

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Correspondence of area and flow

The pipe diameter is 100mm, it corresponds to a rectangular air duct of 80*90mm, 63*125mm, 63*140mm. The areas of rectangular channels will be 72, 79, 88 cm². respectively. The speed of the air flow can be different, the following values ​​​​are usually used: 2, 3, 4, 5, 6 m / s. In this case, the air flow in a rectangular duct will be:

• when moving at 2 m / s - 52-63 m³ / h;
• when moving at 3 m / s - 78-95 m³ / h;
• when moving at 4 m / s - 104-127 m³ / h;
• at a speed of 5 m / s - 130-159 m³ / h;
• at a speed of 6 m / s - 156-190 m³ / h.

If the calculation of ventilation is carried out for a round duct with a diameter of 160 mm, then it will correspond to rectangular air ducts of 100 * 200 mm, 90 * 250 mm with cross-sectional areas of 200 cm² and 225 cm², respectively. In order for the room to be well ventilated, the following flow rate must be observed at certain speeds of air mass movement:

• at a speed of 2 m / s - 162-184 m³ / h;
• at a speed of 3 m / s - 243-276 m³ / h;
• when moving at 4 m / s - 324-369 m³ / h;
• when moving at 5 m / s - 405-461 m³ / h;
• when moving at 6 m / s - 486-553 m³ / h.

Using such data, the question of how is solved quite simply, you just need to decide whether there is a need to use a heater.

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Calculations for the heater

A heater is a piece of equipment designed for air conditioning of a premise with heated air masses. This device is used to create a more comfortable environment in the cold season. Heaters are used in the forced air conditioning system. Even at the design stage, it is important to calculate the power of the equipment. This is done based on the performance of the system, the difference between the outside temperature and the air temperature in the room. The last two values ​​are determined according to SNiPs. At the same time, it must be taken into account that air must enter the room, the temperature of which is not less than +18 ° C.

The difference between outdoor and indoor conditions is determined by taking into account the climatic zone. On average, during switching on, the air heater provides heating of the air up to 40 ° C, in order to compensate for the difference between the warm internal and external cold flow.

I = P / U, where:

• I is the number for the maximum current consumed by the equipment;
• P is the power of the device required for the room;
• U - voltage for powering the heater.

If the load is less than required, then the device must be chosen not so powerful. The temperature at which the air heater can heat the air is calculated using the following formula:

ΔT = 2.98 * P / L, where:

• ΔT is the number of air temperature difference observed at the inlet and outlet of the air conditioning system;
• P is the power of the device;
• L is the value of equipment productivity.

In a residential area (for apartments and private houses), a heater can have a power of 1-5 kW, but for office space, a larger value is taken - this is 5-50 kW. In some cases, electric heaters are not used, the equipment here is connected to water heating, which saves electricity.

On this page, using a special calculator, you can make a calculation based on the parameters you set: type, dimensions, thickness of steel. Enter the height, width and length or diameter of the duct (in millimeters), metal thickness (in millimeters).

The calculator will calculate the approximate price of the product with the specified parameters.

Calculation of the cost of rectangular ducts

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Calculation of the cost of round ducts

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Pricing

The company "VentSystems" pursues a flexible pricing policy aimed at maintaining the minimum selling price of products for customers. Several factors contribute to this. Firstly, the company sells goods of its own production - all goods are made in their own workshops. Therefore, there are no intermediaries and additional monetary markups. Secondly, all work is carried out on modern high-performance equipment that can produce large volumes in a short period. Such technologies make the production process fast and economical, since even the largest orders do not take so much time to complete.

An important factor for pricing is the supply of raw materials. The material for air ducts and fittings is high-quality sheet steel. It is purchased and delivered to the VentSystems plant regularly and in large volumes from the country's leading suppliers. Long-term contracts with sheet steel manufacturers, long-term cooperation and optimal delivery conditions can significantly reduce costs, which favorably affects the cost of production.

The company's management has built and optimized the process of production and sale of goods in such a way as to exclude causes and sources that could unnecessarily increase the cost of products. All functions and tasks are solved using our own resources without involving additional parties. This makes it possible to confidently maintain a balance between the quality of the proposed ventilation products and their affordable cost. Studies show that there are many offers on the market for similar products with prices significantly higher than those presented by us. The opposite problem is cheap air ducts of dubious quality. The VentSystems company is far from both extremes and offers reliable products that meet all standards at reasonable prices.

Special conditions

For all customers, it is possible to discuss individual terms of cooperation. Regular customers have special discounts and offers. In addition, special conditions for the form and terms of payment may apply to individual orders. Large orders can be paid in installments. All organizational issues can be discussed directly with the management of the enterprise. Enterprise "VentSystems" is always ready for any constructive proposals and is interested in fruitful cooperation with all contractors.

The company's management invites representatives of organizations and interested parties to visit the production complex, inspect the plant's workshops, get acquainted with product samples and negotiate with the management. The office and production complex are located in the village of Yam, Domodedovo district, Moscow region.

Aerodynamic calculation of mechanical ventilation and air conditioning systems is carried out to determine the diameters or dimensions of rectangular sections of air ducts or ducts, as well as to determine the pressure loss during air movement in the duct and select the appropriate fan.

One of the important factors in the design of ventilation systems is the speed of air movement in the duct. At high air speed, noise is created from friction against the walls of the duct and turbulence at bends and outlets, and the resistance of the duct system will also increase, which leads to the need to install a fan of greater productivity, and subsequently to an increase in capital and operating costs.

• 1.5 ... 2.0 m / s - in the distribution channel with supply or exhaust ventilation grilles and deflectors;
• 4 ... 5 m / s - for side branches of air ducts for supply and exhaust ventilation;
• 6 m / s - for the main channels of supply and exhaust ventilation;
• 8 ... 12 m / s - for the main channels of industrial enterprises.

For the calculation, an axonometric diagram of the supply and exhaust ventilation systems is built. The main direction of the air ducts in the diagram is divided into sections - segments of the same length and with a constant air flow. Then the sections are numbered and all values ​​​​are applied to the diagram. The total air flow is added up by successive summation of the air flow through the branches that join the main direction.

Calculation of the cross-sectional area of ​​the duct

The calculation of the cross-sectional area of ​​the duct for each section is made according to the following formula:

where L - air flow (m³ / h);

V is the speed of the air flow (m/s);

Then calculate the preliminary diameter of the duct in the area

D=1000∙√(4∙S/"π") mm, and round to the nearest standard size. The dimensions of the air ducts must be taken strictly in accordance with the values ​​\u200b\u200bgiven in the reference manual.

If it is necessary to use rectangular air ducts, the dimensions of the sides are also selected according to the approximate section, i.e. so that a×b ≈ S according to the size table, taking into account that the aspect ratio, as a rule, should not exceed 1:3. The minimum rectangular section is 100×150 mm, the maximum is 2000×2000.

The choice of round or rectangular air ducts and the material from which they will be made is made according to the technical conditions of the facility.

Rectangular ducts are smaller and can be used in rooms with limited space for ventilation ducts. Circular air ducts reduce air resistance and, consequently, the noise of the structure, eliminate air loss and are more convenient for installation.

For your convenience, we have made such a calculation for the most commonly used sizes and cross-sections of air ducts. Address for applications for the selection of equipment for finished projects and the development of Terms of Reference for the design of air conditioning and ventilation systems:

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:

1. "Residential multi-apartment buildings" - SNiP 31-01-2003, paragraph 9.
2. "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 of 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.

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 a kitchen with a 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, dressing room and other 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.

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:

1. 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.
2. 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.
3. 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 the example of a 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 a natural ventilation system, and an additional 100 m³ / h is emitted by a household one.

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.