Online calculation of the diameter of the exhaust ventilation pipe. Features and procedure for calculating exhaust and supply ventilation

In order for the ventilation system in the house to work efficiently, it is necessary to make calculations during its design. This will allow not only the use of equipment with optimal power, but also save on the system, completely preserving all the required parameters. Carried out according to certain parameters, while completely different formulas are used for the natural and forced systems. Particular attention should be paid to the fact that forced system 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 speed of air passing through the air duct;
2.778 is a special factor 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 to power 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.

Natural ventilation of a room is a spontaneous movement of air masses due to the difference in its temperature regimes. in not at home and inside. This type ventilation is divided into ductless and ducted, relatively capable of operation to be continuous and periodic.

The systematic movement of transoms, vents, doors and windows means by the very ventilation procedure. Channelless ventilation, formed on a stable basis in industrial-type rooms with tangible heat emissions, organizing the desired frequency of air mass exchange in the middle of them, this process is called aeration.

in private and high-rise buildings the natural ventilation system of the channel type is more used, the channels in which are located in vertical position in specialized blocks, shafts or located in the walls themselves.

Aeration calculation

Aeration of industrial rooms in summer guarantees the flow of air currents through gaps below gate and entrance doors. In the cool months, admission to the right sizes performed under the means of upper gaps, from 4 m and more above the floor level. Ventilation throughout the whole year was carried out with the help of shafts, deflectors and vents.

In winter, transoms are opened only in areas above the generators enhanced heat release. During the generation of excess apparent heat in the rooms of the building, then temperature regime there is always more air in it than the temperature regime outside the building, and, accordingly, the density is less.

This phenomenon leads to the presence of a pressure difference in the atmosphere. outside and inside rooms. In a plane at a specific height of the room, which is referred to as the plane of equal pressures, this difference is absent, that is, it is equated to zero.

Above this plane, there is some excessive stress, which leads to removing the hot atmosphere to the outside, and below this plane, is the rarefaction that causes the inflow fresh air. The pressure that forces the air masses to move in the process of natural ventilation can be set based on their calculations:

Natural ventilation formula

Pe \u003d (in - n) hg

where n is the air density outside the room, kg/m3;
vn is the density of air masses in the room, kg/m3;
h is the distance between the supply opening and the center of the exhaust, m;
g is the free fall acceleration, 9.81 m/s2.

The method of ventilation (aeration) of buildings with the help of drop-down transoms is considered to be quite correct and effective.

When calculating the natural ventilation of the premises, the establishment of the area of the lower and upper gaps is taken into account. First, the value of the area of the lower gaps is obtained. The building aeration model is set.

Calculation of natural exhaust ventilation

Then, in connection with the opening section of the upper and lower, respectively, supply and exhaust transoms in the room approximately in the center of the height of the structure, the degree of equal pressure is obtained, in this place the influence is exactly the same as zero. In accordance, the influence in the degree of concentration of the lower gaps will be equal to:

where cp is equal to average temperature density of air masses in the room, kg/m3;
h1 is the height from the plane of equal pressures to the lower gaps, m.

At the level of the centers of the upper gaps, above the plane of equal pressures, an excess stress is formed, Pa, equal to:

It is this pressure that affects the air extraction. The total voltage available for the exchange of air flows in the room:

Natural ventilation rate

Air speed in the center of the lower gaps, m/s:

where L is the required exchange of air masses, m3/h;
1 – flow coefficient, depending on the design of the flaps of the lower gaps and the angle of their opening (at 90 opening, = 0.6; 30 - = 0.32);
F1– area of lower gaps, m2

Then the losses, Pa, in the lower gaps are calculated:

Assuming that Pe = P1 + P2 = h(n - cf), and the temperature of the exhaust air tsp = trz + (10 - 15oC), we determine the densities h and cf, which correspond to temperatures tn and tcp.

Excess pressure in the plane of the upper lumens:

Their required area (m2):

F2 \u003d L / (2V22) \u003d L / (2 (2Р2g / cp) 1⁄2)

Calculation and calculation of ventilation ducts

The calculation of a natural ventilation system of a duct type is approaching the establishment of an active section of air ducts, which, in order to access the required amount of air, express a counteraction corresponding to the calculated voltage.

For the longest network path, the voltage costs in the duct channels are set as the sum of the voltage costs in absolutely all of its places. In each of them, pressure costs are formed from friction losses (RI) and costs at counteraction points (Z):

where R is the specific loss of stress along the length of the section due to friction, Pa/m;
l is the length of the section, m.

Air duct area, m2:

where L is the air flow rate, m3/h;
v is the speed of air movement in the duct, m/s (equal to 0.5 ... 1.0 m/s).

Setting the speed of air movement through ventilation, and read the area of its active section and scale. With the help of specialized nomograms or tabular calculations for the rounded shape of air ducts, the stress costs for friction are established.

Natural ventilation calculation of air ducts

For rectangular air ducts of this ventilation concept, the diameter dE is planned to be equal to the rounded air duct:

dE \u003d 2 a b / (a + b)

where, a and b are the length of the sides of a rectangular duct, m.

In the case of using non-metal air ducts, their specific friction pressure costs R, taken from the nomogram for steel air ducts, are changed by multiplying by the corresponding coefficient k:

for slag-gypsum - 1.1;
for slag concrete - 1.15;
for brick - 1.3.

Excess pressure, Pa, to overcome certain resistances for different sections is calculated using the equation:

where - the sum of the coefficients of counteraction on the site;
v2/2 - dynamic stress, Pa, taken from the standards.

To create a concept of relaxed ventilation, it is preferable to beware of tortuous inversions, plural dampers and dampers, since losses due to local resistance usually in air ducts reach up to 91% of all costs.

Natural ventilation contains a small radius of influence and an average efficiency for rooms with very little excess heat, which can be attributed to disadvantages, and the advantage is the ease of the system, low price and ease of maintenance.

Natural ventilation calculation example

Total area - 60 m2;
bathroom, kitchen with gas stove, toilet;
storage room - 4.5 m2;
ceiling height - 3 m.

Concrete blocks will be used for the equipment of air ducts.

Air inflow from the street according to the standards: 60 * 3 * 1 = 180 m3 / hour.

Exhaust air from the room:
kitchens - 90 m3 / hour;
bathroom - 25 m3 / hour;
toilet - 25 m3 / hour;
90 + 25 + 25 = 140 m3/h

The frequency of renewal of air masses in the pantry is 0.2 per 1 / hour.
4.5 * 3 * 0.2 = 2.7 m3/h

Desired air outlet: 140 + 2.7 = 142.7 m3/h.

Ventilation design for residential, public or production building takes place in several stages. Air exchange is determined on the basis of regulatory data, the equipment used and the individual wishes of the customer. The scope of the project depends on the type of building: a one-story residential building or apartment is calculated quickly, with a minimum number of formulas, and serious work is required for a production facility. The method for calculating ventilation is strictly regulated, and the initial data are prescribed in SNiP, GOST and SP.

The selection of the optimal air exchange system in terms of power and cost takes place step by step. The order of design is very important, since the efficiency of the final product depends on its observance:

Determining the type of ventilation system. The designer analyzes the source data. If you want to ventilate a small living space, then the choice falls on supply and exhaust system with a natural urge. This will be enough when the air flow is small, there are no harmful impurities. If it is required to calculate a large ventilation complex for a factory or a public building, then preference is given to mechanical ventilation with the function of heating / cooling the supply, and if necessary, with the calculation of hazards.
Outlier analysis. This includes: thermal energy from lighting fixtures and machine tools; fumes from machine tools; emissions (gases, chemicals, heavy metals).
Calculation of air exchange. The task of ventilation systems is to remove excess heat, moisture, impurities from the premises with an equilibrium or slightly different supply of fresh air. For this, the air exchange rate is determined, according to which the equipment is selected.
Equipment selection. It is produced according to the obtained parameters: the required volume of air for supply / exhaust; indoor temperature and humidity; Availability harmful emissions, ventilation units or ready-made multi-complexes are selected. The most important of the parameters is the volume of air required to maintain the design expansion rate. Filters, heaters, recuperators, air conditioners and hydraulic pumps are included as additional network devices that ensure air quality.

Emission calculation

The volume of air exchange and the intensity of the system depends on these two parameters:

The norms, requirements and recommendations prescribed in SNiP 41-01-2003 "Heating, ventilation and air conditioning", as well as another, more highly specialized normative documentation.
actual emissions. Calculated by special formulas for each source, and are shown in the table:

Heat dissipation, J
Motor electric		N – engine power at nominal value, W; K1 - loading factor 0.7-0.9 k2η - coefficient of work at one time 0.5-1.
Lighting devices
Person		n is the estimated number of people for this room; q is the amount of heat that the body of one person releases. Depends on air temperature and intensity of work.
pool surface		V is the speed of air movement over the water surface, m/s; Т – water temperature, 0 С F – water surface area, m2
Moisture release, kg/h
Water surface, such as a pool		P is the mass transfer coefficient; F-surface area of evaporation, m 2 ; Pn1, Pn2 - partial pressures of saturated water vapor at a certain temperature of water and air in the room, Pa; RB - barometric pressure. Pa.
Wet floor		F is the area of the wet floor surface, m 2; t s, t m - temperatures of air masses, measured by dry / wet thermometer, 0 С.

Using the data obtained as a result of calculating harmful emissions, the designer continues to calculate the parameters of the ventilation system.

Air exchange calculation

Experts use two main schemes:

According to aggregated indicators. This method does not provide for harmful emissions such as heat and water. We will conditionally call it "Method No. 1".
Method taking into account excess heat and moisture. Conditional name "Method No. 2".

Method number 1

The unit of measurement is m 3 / h (cubic meters per hour). There are two simplified formulas:

L=K×V(m 3 /h); L \u003d Z × n (m 3 / h), where

K is the air exchange rate. The ratio of the volume of supply for one hour, to the total air in the room, times per hour;
V is the volume of the room, m 3;
Z is the value of the specific air exchange per unit of rotation,
n is the number of units of measure.

The selection of ventilation grilles is carried out according to a special table. The selection also takes into account average speed passage of air through the channel.

Method number 2

The calculation takes into account the assimilation of heat and moisture. If in production or public building excess heat, then the formula is used:

where ΣQ is the sum of heat releases from all sources, W;
c is the thermal capacity of air, 1 kJ/(kg*K);
tyx is the temperature of the air directed to the exhaust, °С;
tnp - temperature of the air directed to the supply, ° С;
Extract air temperature:

where tp.3 is the normative temperature in working area, 0 С;
ψ - coefficient of temperature increase, depending on the measurement height, equal to 0.5-1.5 0 C / m;
H is the length of the arm from the floor to the middle of the hood, m.

When technological process involves the release of a large amount of moisture, then another formula is used:

where G is the volume of moisture, kg/h;
dyx and dnp - water content per kilogram of dry air supply and exhaust.

There are several cases, described in more detail in the regulatory documentation, when the required air exchange is determined by the multiplicity:

k is the frequency of air changes in the room, once per hour;
V is the volume of the room, m 3.

Section calculation

Square cross section air duct is measured in m 2. It can be calculated using the formula:

where v is the speed of air masses inside the channel, m/s.

It differs for the main air ducts 6-12 m/s and side appendages no more than 8 m/s. Quadrature affects throughput channel, the load on it, as well as the noise level and installation method.

Pressure loss calculation

The walls of the air duct are not smooth, and the inner cavity is not filled with vacuum, so part of the energy of the air masses during movement is lost to overcome these resistances. The amount of loss is calculated by the formula:

where ג is friction resistance, is defined as:

The formulas given above are correct for circular channels. If the duct is square or rectangular, then there is a formula for converting to the diameter equivalent:

where a,b are the dimensions of the sides of the channel, m.

Head and motor power

The air pressure from the blades H must fully compensate for the pressure loss P, while creating the calculated dynamic P d at the outlet.

Fan electric motor power:

Selection of a heater

Often heating is integrated into the ventilation system. For this, heaters are used, as well as the recycling method. Device selection is carried out according to two parameters:

Q in - limiting consumption of thermal energy, W / h;
F k - determination of the heating surface for the heater.

Calculation of gravitational pressure

It is used only for natural ventilation system. With its help, its performance is determined without mechanical stimulation.

Equipment selection

Based on the data obtained on air exchange, the shape and size of the cross-section of air ducts and grilles, the amount of energy for heating, the main equipment is selected, as well as fittings, a deflector, adapters and other related parts. Fans are selected with a power reserve for peak periods of operation, air ducts are selected taking into account the aggressiveness of the environment and ventilation volumes, and heaters and recuperators are selected based on the thermal demands of the system.

Design errors

At the stage of creating a project, errors and shortcomings are often encountered. This may be reverse or insufficient draft, blowing out (upper floors of multi-storey residential buildings) and other problems. Some of them can be solved even after the installation is completed, with the help of additional installations.

A vivid example of a low-skilled calculation is insufficient draft at the exhaust from the production room without particularly harmful emissions. Let's say the ventilation duct ends with a round shaft, rising above the roof by 2,000 - 2,500 mm. Raising it higher is not always possible and advisable, and in such cases the principle of flare emission is used. A tip with a smaller diameter of the working hole is installed in the upper part of the round ventilation shaft. An artificial narrowing of the cross section is created, which affects the rate of gas release into the atmosphere - it increases many times over.

The method of calculating ventilation allows you to get a high-quality internal environment, correctly assessing the negative factors that worsen it. Mega.ru employs professional designers engineering systems any complexity. We provide services in Moscow and neighboring regions. The company is also successfully engaged in remote collaboration. All methods of communication are indicated on the page, please contact.

Proper ventilation in the house significantly improves the quality of human life. With the wrong calculation of inflow - exhaust ventilation there are a lot of problems - for a person with health, for a building with destruction.

Before starting construction, it is imperative and necessary to make calculations and, accordingly, apply them in the project.

PHYSICAL COMPONENTS OF CALCULATIONS

According to the way of work, at present, ventilation schemes are divided into:

Exhaust. To remove used air.
Supply. For clean air intake.
Recovery. Supply and exhaust. Remove the used one and let in the clean one.

V modern world ventilation schemes include various additional equipment:

Devices for heating or cooling the supplied air.
Filters for cleaning odors and impurities.
Devices for humidification and air distribution in rooms.

When calculating ventilation, the following quantities are taken into account:

Air consumption in cubic meters / hour.
Pressure in air channels in atmospheres.
Heater power in kWh.
Cross-sectional area of air channels in sq.cm.

Exhaust ventilation calculation example

Before the beginning exhaust ventilation calculation it is necessary to study the SN and P (System of Norms and Rules) devices of ventilation systems. According to CH and P, the amount of air needed for one person depends on his activity.

Little activity - 20 cubic meters / hour. Average - 40 kb.m./h. High - 60 kb.m./h. Next, we take into account the number of people and the volume of the room.

In addition, you need to know the multiplicity - a complete exchange of air for an hour. For a bedroom, it is equal to one, for household rooms - 2, for kitchens, bathrooms and utility rooms - 3.

For example - calculation of exhaust ventilation rooms 20 sq.m.

Suppose two people live in a house, then:

V (volume) of the room is equal to: SxH, where H is the height of the room (standard 2.5 meters).

V \u003d S x H \u003d 20 x 2.5 \u003d 50 cubic meters.

In the same order, we calculate the performance of exhaust ventilation of the whole house.

Calculation of exhaust ventilation of industrial premises

At calculation of exhaust ventilation of the production room the multiplicity is 3.

Example: garage 6 x 4 x 2.5 = 60 cubic meters. 2 people work.

High activity - 60 cubic meters / hour x 2 \u003d 120 cubic meters / hour.

V - 60 cubic meters. x 3 (multiplicity) = 180 kb.m./h.

We choose more - 180 cubic meters / hour.

As a rule, unified ventilation systems, for ease of installation, are divided into:

100 - 500 cubic meters / hour. - apartment.
1000 - 2000 cubic meters / hour. - for houses and estates.
1000 - 10000 cubic meters / hour. – for factory and industrial facilities.

Calculation of supply and exhaust ventilation

AIR HEATER

Under climate conditions middle lane, the air entering the room must be heated. For this, supply ventilation with heating of the incoming air is installed.

Heating of the coolant is carried out in various ways - with an electric heater, the intake of air masses near the battery or furnace heating. According to SN and P, the temperature of the incoming air must be at least 18 degrees. celsius.

Accordingly, the power of the air heater is calculated depending on the lowest (in the given region) outdoor temperature. The formula for calculating the maximum temperature for heating a room with an air heater:

N / V x 2.98 where 2.98 is a constant.

Example: air consumption - 180 cubic meters / hour. (garage). N = 2 kW.

Thus, the garage can be heated up to 18 degrees. At outdoor temperature minus 15 deg.

PRESSURE AND SECTION

The pressure and, accordingly, the speed of movement of air masses are affected by the cross-sectional area of the channels, as well as their configuration, the power of the electric fan and the number of transitions.

When calculating the channel diameter, the following values are empirically taken:

For residential premises - 5.5 sq.cm. per 1 sq.m. area.
For a garage and other industrial premises - 17.5 sq.cm. per 1 sq.m.

At the same time, flow rates of 2.4 - 4.2 m / s are achieved.

ABOUT ELECTRICITY CONSUMPTION

Electricity consumption directly depends on the duration of the electric heater operation, and the time is a function of the ambient temperature. Usually, the air needs to be heated in the cold season, sometimes in the summer on cool nights. For the calculation, the formula is used:

S = (T1 x L x d x c x 16 + T2 x L x c x n x 8) x N/1000

In this formula:

S is the amount of electricity.

T1 is the maximum daily temperature.

T2 is the minimum night temperature.

L - performance cubic meters / hour.

c - volumetric heat capacity of air - 0.336 W x hour / kb.m. / deg.c. The parameter depends on pressure, humidity and air temperature.

d is the price of electricity during the day.

n is the price of electricity at night.

N is the number of days in a month.

Thus, if you stick to sanitary norms, the cost of ventilation increases significantly, but the comfort of residents improves. Therefore, when installing a ventilation system, it is advisable to find a compromise between price and quality.

It is not always possible to invite a specialist to design a system engineering networks. What to do if during the repair or construction of your facility, the calculation of ventilation ducts was required? Is it possible to make it on your own?

The calculation will make it possible to effective system, which will ensure the uninterrupted operation of units, fans and air handling units. If everything is calculated correctly, this will reduce the cost of purchasing materials and equipment, and subsequently on further maintenance of the system.

Calculation of air ducts of the ventilation system for rooms can be carried out by different methods. For example, like this:

constant pressure loss;
allowed speeds.

Types and types of air ducts

Before calculating networks, you need to determine what they will be made of. Nowadays, products made of steel, plastic, fabric, aluminum foil, etc. are used. Air ducts are often made of galvanized or stainless steel, this can be arranged even in a small workshop. Such products are convenient to mount and the calculation of such ventilation does not cause problems.

In addition, air ducts may differ in appearance. They can be square, rectangular and oval. Each type has its own merits.

Rectangular allow you to make ventilation systems of small height or width, while maintaining the desired cross-sectional area.
There is less material in round systems,
Oval combine the pros and cons of other types.

For example, let's choose round pipes from tin. These are products that are used for ventilation of housing, office and retail space. The calculation will be carried out by one of the methods that allows you to accurately select the network of air ducts and find its characteristics.

Method for calculating air ducts by the method of constant speeds

You need to start with a floor plan.

Using all norms determine right amount air into each zone and draw a wiring diagram. It shows all gratings, diffusers, cross-section changes and taps. The calculation is made for the most remote point of the ventilation system, divided into sections limited by branches or gratings.

The calculation of the air duct for installation consists in choosing the desired section along the entire length, as well as finding the pressure loss for selecting a fan or air handling unit. The initial data are the values of the amount of passing air in the ventilation network. Using the scheme, we will calculate the diameter of the duct. To do this, you need a pressure loss graph.
For each type of air duct, the schedule is different. Usually, manufacturers provide such information for their products, or you can find it in reference books. Let's calculate round tin air ducts, the graph for which is shown in our figure.

Nomogram for size selection

According to the chosen method, we set the air velocity of each section. It must be within the limits for buildings and premises of the selected purpose. For the main air supply and exhaust ventilation ducts, the following values are recommended:

living quarters - 3.5–5.0 m/s;
production - 6.0–11.0 m/s;
offices - 3.5–6.0 m/s.

For branches:

offices - 3.0–6.5 m/s;
living quarters - 3.0–5.0 m/s;
production - 4.0–9.0 m/s.

When the speed exceeds the permissible level, the noise level rises to an uncomfortable level for a person.

After determining the speed (in the example 4.0 m/s), we find the desired section of the air ducts according to the graph. There are also pressure losses per 1 m of the network, which will be needed for the calculation. The total pressure loss in Pascals is found by multiplying the specific value by the length of the section:

Manual=Man·Man.

Network elements and local resistances

Losses on network elements (lattices, diffusers, tees, turns, changes in section, etc.) are also important. For lattices and some elements, these values are specified in the documentation. They can also be calculated by multiplying the coefficient local resistance(c.m.s.) on dynamic pressure in him:

Rm. s.=ζ Rd.

Where Rd=V2 ρ/2 (ρ is the air density).

K. m. s. determined from reference books and factory characteristics of products. We summarize all types of pressure losses for each section and for the entire network. For convenience, we will do this in a tabular way.

The sum of all pressures will be acceptable for this duct network and the branch losses must be within 10% of the total available pressure. If the difference is greater, it is necessary to mount dampers or diaphragms on the outlets. To do this, we calculate the required c.m.s. according to the formula:

ζ= 2Rizb/V2,

where Pizb is the difference between available pressure and branch losses. According to the table, select the diameter of the diaphragm.

The required diameter of the diaphragm for air ducts.

The correct calculation of ventilation ducts will allow you to choose the right fan by choosing from manufacturers according to your criteria. Using the found available pressure and the total air flow in the network, this will be easy to do.