Calculation of ventilation in the building Example. How to calculate the supply and exhaust ventilation system of industrial premises. Calculator calculating the required amount of air inflows for normal ventilation

The microclimate of the premises of the building of any destination must comply with sanitary and hygienic standards to ensure the optimal or permissible mode of operation or human activity. The parameters of the microclimate preferably provide systems for supply ventilation, and its calculation is reduced to the determination of the amount of supply air.

Harmful discharges affecting the microclimate of the premises

The composition and number of harmfulness allocated to the room depends on the functional purpose of the building and the technological processes occurring in it. In residential and public buildings only there are allocations from the vital activity of people, while in the production premises the composition of the harm can be whatever, it all depends on the technological process. All hazards are divided into several types:

Harmfulness of human vital activity (moisture isolation, carbon dioxide, heat).
Allocation of harmful vapors or aerosols of various substances during the technological process. The high concentration of these substances has a detrimental effect on the health of people working in the room.
In production buildings, technological processes with increased highlighting of water vapor, which causes high humidity and condensate falling on cold surfaces. Such conditions for work do not correspond to sanitary standards.
Heat outlook from preheated technological equipment or products. Surplus heat acting on human health during the work shift, also have a negative impact on it.

For civilian buildings, the calculation is implemented, as a rule, the harmfulness specified in paragraph 1. In industrial buildings, it is required to calculate the amount of supply air required to reduce the concentration of each of the types of harmful discharges, and make a value from the greatest results.

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Calculation of enlarged indicators

The enlarged indicators for the calculation reflect the flow of supply air per unit of room volume, one person or one source of harmful discharges. The parameters of the microclimate in the premises of civil buildings are governed by sanitary standards and requirements. For each type of building, there are regulations, they indicate the values \u200b\u200bof the multiplicity of air exchange for rooms of various purposes. In this case, the calculation is made by the formula:

V - the size of the room, m3;
k is the multiplicity of air exchange at 1 hour.

The multiplicity is the number that shows how many times in one hour the air in the room will be completely updated. With a value of 1, the amount of air will be equal to the volume of the room. In other cases that do not take into account these standards, there are indicators of the optimal amount of supply air per person. These standards are prescribed in SNIP 41-01-2003 and are 30 m3 / h for ventilated rooms per person, and for non-refined - 60 m3 / h. Then the formula is used to calculate:

L is the required amount of outdoor air for the tributary, m3 / h;
N - the number of people constantly located in indoors;
m is the number of inflow per person per hour.

The calculation for this formula is also acceptable if other types of harmful discharge into the space of a production room are very insignificant. When there is one or more identical sources, from which harmful pairs or aerosols proceed, the calculation method according to enlarged indicators is applicable, provided that the number of outdoor air is known for each of them. Then the value M will show the value of the inflow by 1 source, and the N parameter in the formula means their number.

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Description of calculation methods

If there are many sources in an industrial building, which during the technological process emit pairs of harmful substances, it is required to spend each of these substances. For this, it is found out exactly which substances are allocated in what quantity, after which it is possible to calculate the concentration of 1 m3 within the same room and compare it with the value of the maximum permissible concentration (MPC) for each type of substances. These values \u200b\u200bare set by regulatory documentation. In case of exceeding the PDC, calculate the number of inflows that ventilation systems should provide. To do this, use the formula:

L \u003d MB / yd - y0, where:

L is the required value of the inflow, M3 / h;
MB is the intensity of excretion of the harmful substance per unit of time, mg / h;
ydop - the concentration of this substance in the air of the room, mg / m3;
y0 is its concentration in the supply air, mg / m3.

They consider the value of the inflow for each harmful selection, after which they are taken for ventilation the largest of the results.

For neutralization of excess heat, the following formula is used to determine the validity of the inflow:

L \u003d LMO +

In this formula, the parameters:

LMO - the exhaust volume from the working or serviced zone (the work area takes the space to a height of 2 m from the zero mark of clean floors) by local suction or technological needs, M3 / h;
Q - the amount of heat from the technological equipment or preheated products, W;
tMO - the temperature of the air mixture, which is removed by the system of local suns from the working area, ⁰c;
tpom - the temperature of the air mixture, removed from the remaining part of the room above the working zone by exhaust ventilation, ⁰С;
tP is the temperature of the treated supply air, ⁰c;
C is the heat capacity of the air mixture, 1.2 kJ (M3⁰C) is accepted.

Excessive heat from the technological processes is removed using an exhaust system and, as a rule, is used again (recycling).

Regular requirements are presented to working conditions in production and industry. Various standards must be respected. Proper fulfillment of many requirements affects the quality of the air environment. It provides the right air exchange. On most industrial enterprises it cannot be provided at the expense of natural ventilation, so the installation of special hoods is required. To properly establish air exchange, you need to calculate ventilation.

Types of air exchange used in industrial enterprises

Industrial ventilation systems

Regardless of the type of production, the quality of air at any enterprise is presented fairly high demands. There are standards for the content of various particles. To fully fulfill the requirements of sanitary standards, various types of ventilation systems have been developed. The quality of air is dependent on the type of air exchange. Currently, the following types of ventilation are used in production:

aeration, that is, general ventilation with a natural source. It regulates air exchange in the entire room. It is used only in large industrial premises, for example, in workshops without heating. This is the oldest type of ventilation, is currently used less often and less often, as it does not work well with air pollution and is not able to adjust the temperature mode;
the local exhaust, it is used in the production where there are local sources of emissions of harmful, polluting and poisonous substances. It is installed in close proximity to emission locations;
supply-exhaust ventilation with artificial motivation used to regulate air exchange on large areas, in workshops, in various rooms.

Ventilation functions

Currently, the ventilation system performs the following functions:

removal of production harmful substances allocated during operation. Their content in the air in the working area is governed by regulatory documents. For each type of production, their requirements are established;
removal of excess moisture in the working area;
filtering of a dirty airborne indoor room;
release of remote pollutants to the height necessary for dispersion;
regulation of temperature regime: removal of air heated during the production process (heat is highlighted from working mechanisms, heated raw materials, substances entering chemical reactions);
filling with air from the street, while filtering is carried out;
heating or cooling of retractable air;
moisturizing air inside the production premises and drawn from the street.

Types of air pollution

Before proceeding with the settlement work, it is necessary to find out which sources of pollution are available. Currently, the following types of harmful discharge are found at work:

excess heat from working equipment, heated substances and so on;
evaporation, pairs and gases containing harmful substances;
excretion of explosive gases;
excess moisture;
allocations from people.

As a rule, there are various types of contamination in modern industries, such as working equipment and chemicals. And none of the productions can do without discharge from people, since in the process of activity a person breathes, the smallest particles of the skin are creepy, and so on.

The calculation must be performed on each of the types of pollution. At the same time, they are not summarized, but are taken for the final greatest result of calculations. For example, if you most need air to remove chemical air pollution, it is this calculation and will be accepted to calculate the required volume of secrementary ventilation and exhaust power.

Execution of calculations

As can be seen from the foregoing, ventilation performs many different functions. To ensure high-quality air purification can only be enough devices. Therefore, when installing, you must calculate the necessary power of the installed exhaust. Do not forget that various types of ventilation systems use for different purposes.

Calculation of local exhaust

If there are emissions of harmful substances in production, they need to be trapped directly at the most close distance from the source of pollution. This will make them removal more efficient. As a rule, various technological containers become sources of emissions, also to contaminate the atmosphere. To capture the distinguished harmors use local exhaust devices - suction. Usually they have the kind of umbrella and are installed above the source of vapors or gases. In some cases, such installations are included with the equipment, in other - power and sizes are calculated. It is easy to fulfill, if you know the correct calculation formula and have some source data.

To make the calculation, you need to spend some measurements and find out the following parameters:

size of the source of the emission, the length of the parties, section, if it has a rectangular or square shape (parameters A x b);
if the source of pollution has a round shape, it is necessary to know its diameter (parameter D);
air movement speed in the zone where the emission is released (parameter VV);
suction rate in the area of \u200b\u200bthe exhaust system (umbrella) (parameter VZ);
the planned or existing exhaust installation height over the source of the contamination (parameter Z). It should be remembered that the closer the exhaust to the source of the emission is located, the more effective pollutants are collected. Therefore, the umbrella needs to be as low as possible above the tank or equipment.

The calculation formulas for rectangular hoods look like this:

A \u003d a + 0.8zwhere A is the side of the ventilation device, A is the side of the contamination source, Z is the distance from the emission source to the exhaust.

B \u003d B + 0.8Zwhere B is the side of the ventilation device, B is the side of the contamination source, Z is the distance from the emission source to the exhaust.

If the exhaust installation will have a round shape, its diameter is calculated. Then the formula will look like this:

D \u003d d + 0.8zwhere D is the drawing diameter, the d-diameter of the contamination source, z- distance from the emission source to the exhaust.

The exhaust device is made in the form of a cone, and the angle should be no more than 60 degrees. Otherwise, the effectiveness of the ventilation system will decrease, since zones are formed along the edges where air is formed. If the indoor air velocity indicators are more than 0.4 m / s, the cone must be equipped with special folding aprons to prevent dispersion of the substances and protect them from external influence.

Know the overall drawing dimensions are necessary, since the quality of the air exchange will depend on these parameters. It is possible to determine the amount of exhaust air by the following formula: L \u003d 3600VZ X SZwhere the air flow rate (M 3 / h) is understood, the air velocity in the exhaust device (to determine this parameter, a special table is used), Sz is an area of \u200b\u200bopening of the ventilation unit.

If the umbrella has a rectangular or square shape, then its area is calculated by the formula S \u003d A * Bwhere A and B are the parties of the figure. If the exhaust device has a circle form, its size is calculated by the formula S \u003d 0,785dwhere D is the diameter of the umbrella.

The results should be taken into account when designing and calculating the general ventilation.

Calculation of secrerative supply-exhaust ventilation

When the required volume and parameters of the local exhaust, as well as the volumes and types of contamination, can be attached to the calculation of the required volume of air exchange in the production room.

The easiest option when when working there are no harmful allocations of various types, and there are only those pollutants that highlight people. The optimal amount of clean air will provide normal working conditions, compliance with sanitary standards, as well as the necessary purity of the technological process.

To calculate the required amount of air for working people, use the following formula: L \u003d N * Mwhere L is the required amount of air (m 3 / h), n is the number of working people in the production site or in a particular room, M is air flow for breathing 1 person per hour.

The specific air flow per hour per hour is a fixed value designated in special slips. The norms state is indicated that the volume of the mixture of 1 person is 30 m 3 / h, if the room is carried out if there is no possibility, then the norm becomes twice as much and reaches 60 m 3 / h.

It is more difficult for the fact that there are various sources of emissions of harmful substances on the site, especially if there are many of them and they are dispersed on a large area. In this case, local hoods will not be able to fully get rid of harmful substances. Therefore, production is often resorted to the next reception.

Emissions are dispersed, and then removed with the help of secrerative supply-exhaust ventilation. All harmful substances are installed their MPC (maximum permissible concentrations), with their values \u200b\u200bcan be found in the special literature, as well as regulatory documents.

L \u003d MB / (YP - YP)where L is the required amount of fresh air, MV is a mass of a harmful substance (mg / h), by pack - the specific concentration of the substance (mg / m 3), the supplied substance concentration in the air entering the ventilation system.

If several types of pollutants are distinguished, then it is necessary to calculate the required amount of pure air mixture for each of them, and then summarize them. The result will be the total air volume, which should be included in the production room to ensure the implementation of sanitary requirements and normal working conditions.

Calculation of ventilation is a difficult matter requiring great accuracy and special knowledge. Therefore, it is possible to use online services for independent computing. If production has to work with dangerous and explosives, it is better to trust the calculation of ventilation by professionals.

It is known that the definition of the quantitative parameters of the air exchange is made according to the dominant species of harmful discharge in industrial buildings (for heat, on water vapor, harmful gases and vapors, taking into account their summation under the action per person).

Depending on the technological features of production processes, to ensure the parameters of the microclimate in industrial premises often use simultaneous operation of general and local supply and exhaust systems.

Local air ventilation systems are combined into the system:

· By technological lines of production,

· By simultaneity of equipment,

· By type of harmful discharge,

· Optimal range radii and air costs.

Local exhaust ventilation is a set of interrelated and interacting components of such as storming substances in technological equipment, technological equipment and a set of elements and devices intended for localizing the distinguished harmfulness and removal of contaminated air outside the room.

The main elements of local ventilation exhaust systems are:

· Local compounds - devices intended for the fence of harmful substances from technological equipment or their places of education;

· Branch;

· Main duct.

Depending on whether the mechanical or gravitational system, its composition, if necessary, can be included cleansing equipment (filters, dust collectors, cyclones) and ventilation unit.

The formation of harmful substances in the air of industrial premises imposes the following requirements for the organization of air exchange:

1. Supply jets should not cross the trajectory of the torch of local suns;

2. It is forbidden to install air distributors over technological equipment and technological lines;

3. Air ducts of supply systems should be placed in places that do not interfere with technological production;

4. Air distributors should be located above work seats and drives to provide the required meteo conditions in the working area in such a way that there is a minimum trajectory from the air distributor to the human respiratory zone;

5. The type of air distribution devices is determined by the type of technological operations and the peculiarities of the production in the room.

The concentration of harmful substances in air, removed by local exhaust systems, exceeds the concentration of these substances in the air, removed by generally exchange systems, therefore the efficiency of local exhaust systems to remove harm is higher than that of the general. Community systems to achieve the same effect should have significantly high costs, so local exhaust systems are not climatic, they are technological ventilation systems.

Requirements for local suction.

Sanitary and hygienic requirements - Requirements defining

the need for full capturing by local suction of the distinguished harmful substances and eliminating them to the human respiratory zone to maintain the required climatic conditions in the working area.

Technological requirements:

1) local suction must completely cover the place of formation of harmful substances and have a minimum technological opening (working opening) for maintenance of processes;

2) local suction must be located in places providing maximum labor productivity and safety of technological processes;

3) local specks must have minimal aerodynamic resistance;

4) the removal of harmful substances should coincide with the direction of the inertial forces of harmful substances;

5) Local compounds must be made by industrial methods and easily dismantled.

Classification of local suns.

There is the following conditional classification of local suns:

· Semi-open;

· Open;

· Fully closed.

Semi-open local suction - Local complies that fully cover the formation of harmful substances and having a working opening for maintenance of technological processes (exhaust cabinets and exhaust cameras).

Open local surroundings - Local compounds located outside of technological equipment and technological line (umbrellas, umbrella-visors, onboard suctions).

Fully closed local suction - Local compounds that are part of the technological equipment casing. For air fence, they have special sloping holes in the casing.

When choosing a suction scheme and in its constructive work, it is necessary to be guided by the following main provisions:

· SUPP should be as close as possible to the source and, if possible, isolate the source from the room;

· The best solve is the full shelter of the source;

· A suction hole should be focused so that the flow of harmful discharges is minimally deviated from the initial direction of movement and at the same time removed air did not pass through the breathing zone of the operating.

· A decrease in the size of the receiving opening of the suction leads to an increase in the flow of air required to capture harmful discharges.

Air flow rate for suction from the source separating heat and gases is proportional to the characteristic flow rate in the convective stream, rising above the source:

where L. 0 - characteristic consumption, m3 / h;

k. P - a dimensionless multiplier, taking into account the effect of geometric

and regime parameters characterizing the "Source - Source" system;

k. in a coefficient, taking into account the effect of air velocity at the room;

k. T - the coefficient that takes into account the toxicity of harmful fission.

For suns from shelters having workers and looseness, also use the formula

, (..)

where F.-The bottom of working openings and looseness, m2;

v. 0 -Iwer on the area of \u200b\u200bwork openings and looseness of suction rate, m / s.

Air speed v. o depends on the nature of the technological process and the toxicity of harmful discharge and is usually determined experimentally.

When calculating suns from heat sources, it is necessary to know their convective heat transfer, which is calculated by the formulas:

· Horizontal surface

· Vertical surface

where - temperatures of the heated surface and air indoors, ° C;

And - the area of \u200b\u200bhorizontal and vertical surfaces of the source ,.

The value of the coefficient n.accepted depending on:

, ° С ......... .. 50 100 200 300 400 500 1000

n ..................1,63 1,58 1,53 1,45 1,4 1,35 1,18

When calculating suns from volumetric heat sources, total heat transfer of all surfaces is adopted.

Local ventilation is used in all cases where harmful substances are excreted as a result of the technological process, when processing metal cutting, welding, casting, blacksmith, thermal, painting, tire-repair, medical work, as well as with metal soldering, charging batteries, chemical processes and other types of work.

The removal of harmful substances can be carried out using various gas-peilers located on equipment or workplace, where harmful substances are isolated (or using suns built into equipment or into separate elements). For example, on the welding machines ADS-1000-zo, ACSU 6m, welding burners E.M. Tupper, on semi-automatic agents A-537, A-547, PSh-5U, cutters-dustsworth-actuators of the design of the design of VCNNIOT, on sharpened grinding and other metalworking machines, etc.

Dwarf-receiver can be different types: closed (exhaust cabinets), semi-closed (umbrellas) and open (uniform suction panels). The technical characteristics of some suns for stationary and non-stationary welding posts are shown in the table.

3.1. Calculation of exhaust umbrellas. The volume of air exhausted by the exhaust umbrella is determined by the formula

a and b - the size of the umbrella in the plan, m;

V. - the rate of suction air in the secting plane over the edge of the umbrella (intake opening of the umbrella), usually V. Accepted from 0.5 to 1.5 m / s, depending on the construction of the umbrella. According to GOST 12.2.046-80 "Foundry equipment. GENERAL SAFETY REQUIREMENTS: The rate of exhausted air for exhaust casing of casting conveyors is taken with 4 m / s, galloping drums in a pin up to 24 m / s, emotion machines 30% of the circumferential speed, but not less than 2 m / s per mm circle diameter.

3.2. Calculation of exhaust cabinets. The volume of air removed from exhaust cabinets is determined by the formula

F. - the area of \u200b\u200bthe work opening (open openings and looseness) ,;

v is the speed of air supply through open working holes, m / s.

For welding work v. Take on the table.

3.3 Number of air removed from polished and polishing machines,

where dKP. - circle diameter, mm;

k. - the coefficient taken depending on the material and

circle diameter;

n.- number of circles.

For grinded circles: when dKP. \u003d 250 mm k. \u003d 1.6. For mothers polishing circles k.\u003d 6, for felt polishing circles k. = 4.

3.4. To determine the flow of air removed by local suction at semi-automatic welding, you can apply the formula

where TO - an experimental coefficient of 12 for slotted suits and 16 for dual suction;

I. - The magnitude of the welding current.

Table 3.1.

Estimated air velocity with various technological operations and types of local suns

The quality of the air environment in the workshops is regulated by law, the standards are established in SNiP and TB. On most objects, effective air exchange cannot be formed by means of a natural system, and equipment must be installed. It is important to achieve regulatory indicators. For this, the calculation of the supply and exhaust ventilation of the production room.

The standards provide for various types of pollution:

excessive heat from the operation of machines and mechanisms;
evaporation in which harmful substances are contained;
excess humidity;
various gases;
human discharge.

The calculation technique offers analysis for each of the contaminants. The results are not summed up, and the work is made the greatest value. So, if at the production of the maximum volume is needed to remove excess heat, it is this indicator that is accepted for calculating the technical parameters of the structure. We give an example of calculating the ventilation of the production room, with an area of \u200b\u200b100 m 2.

Air exchange at an industrial platform, an area of \u200b\u200b100 m 2

The following functions should be performed in production:

remove harmful substances;
clean the medium from pollution;
remove excess moisture;
remove harmful emissions from the building;
adjust the temperature mode;
shape the influx of pure stream;
depending on the features of the site and weather conditions, heated moisturize or cool the incoming air.

Since each function requires additional power from the ventilation structure, so the equipment selection should be made with regard to all indicators.

Local exhaust

If in the technological processes of production in one of the sections there are emissions of harmful substances, then next to the source, according to the standards you need to install a local exhaust. So removal will be more efficient.

Most often, this source is technological tanks. For such objects, special installations are used - suction in the form of umbrellas. Its sizes and power are calculated using the following parameters:

source dimensions depending on the form: the length of the parties (A * B) or the diameter (D);
flow rate in the source zone (VV);
installation absorption rate (VZ);
the height of the placement of suction above the tank (Z).

The sides of the rectangular suction are calculated by the formula:
A \u003d a + 0.8z,
where a is the side of the suction, A is the side of the tank, Z is the distance between the source and the device.

The parties of the round device are calculated by the formula:
D \u003d d + 0.8z,
Where D. - Device diameter, D - source diameter, Z is the distance between the suction and the tank.

Preferably has a cone form, the angle of which should not exceed 60 degrees. If there is more than 0.4 m / s in the workshop, then the device should be equipped with apron. The amount of exhaust air is installed by the formula:
L \u003d 3600VZ * SA,
Where L. - Air consumption in M3 / hour, VZ - flow rate in the hood, SA is the work area of \u200b\u200bthe suction.

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The result should be taken into account in the design and calculations of the promise system.

Community ventilation

When the local exhaust calculation is made, the types and volumes of pollution, you can make a mathematical analysis of the desired volume of air exchange. The easiest option when there is no technological pollution on the site, and only human discharge is accepted into calculations.

In this case, the task is to achieve sanitary standards and purity of production processes. The required volume for employees is calculated by the formula:
L \u003d n * m,
where L is the amount of air in m 3 / hour, n is the number of employees, M is the volume of air per person for an hour. The last parameter is normalized by SNiP and is 30 m 3 / hour - in a ventilated workshop, 60 m 3 / hour in closed.

If harmful sources exist, the task of the ventilation system to reduce contamination to the limit norms (MPC). Mathematical analysis is performed by the formula:
O \u003d mV \\ (ko - kp),
Where o is air flow, MV - the mass of harmful substances that are released into the air in 1 hour, the concentration of harmful substances, KP - the number of pollution in the influx.

The influx of contaminants is also calculated, for this I use the following formula:
L \u003d MV / (YP - YP),
where L is the volume of the inflow in M3 / hour, MV is the weight value of harmful substances that are released into the MG / H per hour, the specific concentration of pollutants in m3 / hour, YP is a concentration of contamination from the supply air.

The calculation of the general ventilation of industrial premises does not depend on its area, other factors are important here. Mathematical analysis for a specific object is complicated, it needs to take into account many data and variables, you should use special literature and tables.

Forced ventilation

Calculation of industrial premises is advisable to perform by integrated indicators, which express the flow of incoming air per unit volume of the room, per person or 1 source of pollution. The standards establishes their norms for various production.

The formula is such:
L \u003d VK.
where L is the volume of the supply masses in m 3 / hour, V is the volume of the room in m 3, k - the multiplicity of air exchange.
For the room, with an area of \u200b\u200b100 m 3 and 3 meters high for a 3-fold air shift, it will be necessary: \u200b\u200b100 * 3 * 3 + \u003d 900 m 3 / hour.

The calculation of exhaust ventilation of industrial premises is carried out after determining the desired volumes of the supply mass. Their parameters must be similar, so for the object, with an area of \u200b\u200b100 m 3 with the height of the ceilings in 3 meters and three-time exchanging the exhaust system should pump the same 900 m 3 / hour.

Design includes a lot of aspects. It all starts with the preparation of a technical task, which determines the orientation of the object on the parties of light, appointment, layout, materials of the building structures, features of the technologies used and the mode of operation.

Computing volumes are large:

climatic indicators;
multiplicity of air exchange;
the distribution of air masses inside the building;
determination of air ducts, including their forms, location, capacities and other parameters.

The general diagram is then compiled, and the calculations continue. At this stage, nominal pressure in the system and its loss, the level of noise at the production, the length of the air duct system, the number of bends and other aspects are taken into account.

Summarize

Correct mathematical analysis To determine the parameters of air exchange options, only a specialist can be made using various data, variables and formulas.

Independent work will lead to errors, and as a result: impaired sanitary standards and technological processes. Therefore, if there is no specialist with the proper level of qualifications in your company, it is better to use the services of a profile company.