What determines the air regime of the building. Air mode of a modern building. Air and radiation regime of the room

18.10.2019

The air regime of a building is a set of factors and phenomena that determine general process air exchange between all its premises and outside air, including the movement of air inside the premises, the movement of air through fences, openings, channels and air ducts and the flow of air around the building. Traditionally, when considering individual issues of the air regime of a building, they are combined into three tasks: internal, regional and external.

The general physical and mathematical formulation of the problem of the air regime of a building is possible only in the most generalized form. The individual processes are very complex. Their description is based on the classical equations of mass, energy, momentum transfer in a turbulent flow.

From the position of the specialty “Heat supply and ventilation”, the following phenomena are most relevant: infiltration and exfiltration of air through external fences and openings (unorganized natural air exchange, which increases the heat loss of the room and reduces the heat-shielding properties of external fences); aeration (organized natural air exchange for ventilation of heat-stressed premises); air flow between adjacent rooms (unorganized and organized).

The natural forces that cause air movement in a building are gravity and wind pressure. The temperature and air density inside and outside the building are usually not the same, as a result of which the gravitational pressure on the sides of the fences is different. Due to the action of the wind, a backwater is created on the windward side of the building, and excess static pressure occurs on the surfaces of the fences. On the windward side, a rarefaction is formed and the static pressure is reduced. Thus, with wind, the pressure from the outside of the building differs from the pressure inside the premises.

Gravitational and wind pressures usually act together. Air exchange under the influence of these natural forces is difficult to calculate and predict. It can be reduced by sealing the fences, and also partially regulated by throttling the ventilation ducts, opening windows, transoms and ventilation lights.

The air regime is related to the thermal regime of the building. The infiltration of outdoor air leads to additional heat costs for its heating. Exfiltration of humid indoor air moisturizes and reduces the heat-shielding properties of fences.

The position and dimensions of the infiltration and exfiltration zone in the building depend on the geometry, design features, the mode of ventilation of the building, as well as the construction area, season and climate parameters.

Between the filtered air and the fence, heat exchange occurs, the intensity of which depends on the place of filtration in the structure of the fence (array, panel joint, windows, air gaps, etc.). Thus, there is a need to calculate the air regime of the building: determining the intensity of air infiltration and exfiltration and solving the problem of heat transfer of individual parts of the fence in the presence of air penetration.

Method for calculating the air permeability resistance of the wall enclosing structure

1. Determine the specific gravity of outdoor and indoor air, N / m 2

. (6.2)

2. Determine the difference in air pressure on the outer and inner surfaces of the building envelope, Pa

3. Calculate the required resistance to air penetration, m 2 × h × Pa / kg

4. Find the total actual resistance to air penetration of the outer fence, m 2 × h × Pa / kg

If the condition is met, then the enclosing structure meets the requirements of air permeability, if the condition is not met, then it is necessary to take measures to increase air permeability.

Calculation of air permeability resistance
wall enclosing structure

Initial data

The values of the quantities required for the calculation: the height of the enclosing structure H = 15.3 m; t n = –27 °С; t c = 20 °С; V cold= 4.4 m/s; G n \u003d 0.5 kg / (m 2 × h); R u1 \u003d 3136 m 2 × h × Pa / kg; R u2 \u003d 6 m 2 × h × Pa / kg; R u3 \u003d 946.7 m 2 × h × Pa / kg.

Calculation procedure

Determine the specific gravity of outdoor and indoor air according to equations (6.1) and (6.2)

N/m 2 ;

N/m 2 .

Determine the difference in air pressure on the outer and inner surfaces of the building envelope, Pa

Δp \u003d 0.55 × 15.3 × (14.1 - 11.8) + 0.03 × 14.1 × 4.4 2 \u003d 27.54 Pa.

Calculate the required air permeation resistance according to equation (6.4), m 2 × h × Pa / kg

27.54 / 0.5 \u003d 55.09 m 2 × h × Pa / kg.

Find the total actual resistance to air penetration of the outer fence according to equation (6.5), m 2 × h × Pa / kg

m 2 × h × Pa / kg;

M 2 × h × Pa / kg.

Thus, the enclosing structure meets the requirements of air permeability, since the condition (4088.7>55.09) is fulfilled.

The method for calculating the resistance to air penetration of external fences (windows and balcony doors)

Determine the required air permeability of windows and balcony doors, m 2 × h × Pa / kg

, (6.6)

Depending on the value, choose the type of construction of windows and balcony doors.

Calculation of air permeation resistance of external fences, windows and balcony doors

Initial data

p= 27.54 Pa; Δ p 0 = 10 Pa; G n \u003d 6 kg / (m 2 × h).

Calculation procedure

Determine the required air permeability of windows and balcony doors, according to equation (6.6), m 2 × h × Pa / kg

m 2 × h × Pa / kg.

Thus, one should take R 0 = 0.4 m 2 × h × Pa / kg for double glazing in paired bindings.

6.3. Methodology for calculating the effect of infiltration
to the temperature of the inner surface
and heat transfer coefficient of the building envelope

1. Calculate the amount of air penetrating through the outer fence, kg / (m 2 × h)

2. Calculate the temperature of the inner surface of the fence during infiltration, °С

, (6.8)

. (6.9)

3. Calculate the temperature of the inner surface of the fence in the absence of condensation, ° С

. (6.10)

4. Determine the heat transfer coefficient of the fence, taking into account infiltration, W / (m 2 × ° С)

. (6.11)

5. Calculate the heat transfer coefficient of the fence in the absence of infiltration according to equation (2.6), W / (m 2 × ° С)

Calculation of the effect of infiltration on the temperature of the inner surface
and heat transfer coefficient of the building envelope

Initial data

Values of quantities required for calculation: Δ p= 27.54 Pa;
t n = –27 °С; t c = 20 °С; V cold= 4.4 m/s; \u003d 3.28 m 2 × ° C / W; e= 2.718; \u003d 4088.7 m 2 × h × Pa / kg; R c \u003d 0.115 m 2 × ° C / W; With B \u003d 1.01 kJ / (kg × ° C).

Calculation procedure

Calculate the amount of air penetrating through the outer fence, according to equation (6.7), kg / (m 2 × h)

G and \u003d 27.54 / 4088.7 \u003d 0.007 g / (m 2 × h).

Calculate the temperature of the inner surface of the fence during infiltration, °C, and the thermal resistance to heat transfer of the building envelope, starting from the outside air to a given section in the thickness of the fence according to equations (6.8) and (6.9).

m 2 × ° C / W;

Calculate the temperature of the inner surface of the fence in the absence of condensation, ° С

°C.

It follows from the calculations that the temperature of the inner surface during filtration is lower than without infiltration () by 0.1 °C.

Determine the heat transfer coefficient of the fence, taking into account infiltration according to equation (6.11), W / (m 2 × ° C)

W / (m 2 × ° C).

Calculate the heat transfer coefficient of the fence in the absence of infiltration according to equation (2.6), W / (m 2 C)

W / (m 2 × ° C).

Thus, it was found that the heat transfer coefficient, taking into account infiltration k and more than the corresponding coefficient without infiltration k (0,308 > 0,305).

test questions to section 6:

1. What is the main purpose of calculating the air regime of an external fence?

2. How does infiltration affect the temperature of the inner surface
and the heat transfer coefficient of the building envelope?

7. Requirements for building consumption

7.1 Methodology for calculating the specific characteristic of the consumption of thermal energy for heating and ventilation of the building

An indicator of the consumption of thermal energy for heating and ventilation of a residential or public building at the stage of development of project documentation is the specific characteristic of the consumption of thermal energy for heating and ventilation of the building, numerically equal to the consumption of thermal energy per 1 m 3 of the heated volume of the building per unit time with a temperature difference of 1 ° C, , W / (m 3 0 C). The calculated value of the specific characteristic of the consumption of thermal energy for heating and ventilation of the building, W / (m 3 0 C), is determined by the method, taking into account the climatic conditions of the construction area, the selected space-planning decisions, the orientation of the building, the heat-shielding properties of the building envelope, the adopted system ventilation of the building, as well as the use of energy-saving technologies. The calculated value of the specific characteristic of the consumption of thermal energy for heating and ventilation of the building must be less than or equal to the normalized value, according to , , W / (m 3 0 С):

where is the normalized specific characteristic of the consumption of thermal energy for heating and ventilation of buildings, W / (m 3 0 С), determined for various types residential and public buildings according to table 7.1 or 7.2.

Table 7.1

thermal energy for heating and ventilation

Notes:

With intermediate values of the heated area of the building in the range of 50-1000m 2, the values should be determined by linear interpolation.

Table 7.2

Normalized (basic) specific flow characteristic

thermal energy for heating and ventilation

low-rise residential single-apartment buildings, W / (m 3 0 С)

building type	Floors of the building
			4,5	6,7	8,9	10, 11	12 and up
1 Residential multi-apartment, hotels, hostels	0,455	0,414	0,372	0,359	0,336	0,319	0,301	0,290
2 Public, other than those listed in lines 3-6	0,487	0,440	0,417	0,371	0,359	0,342	0,324	0,311
3 Polyclinics and medical institutions, boarding schools	0,394	0,382	0,371	0,359	0,348	0,336	0,324	0,311
4 Preschools, hospices	0,521	0,521	0,521	-	-	-	-	-
5 Service, cultural and leisure activities, technology parks, warehouses	0,266	0,255	0,243	0,232	0,232
6 Administrative purposes (offices)	0,417	0,394	0,382	0,313	0,278	0,255	0,232	0,232

Notes:

For regions with a GSOP value of 8000 0 C day or more, the normalized ones should be reduced by 5%.

To assess the energy demand for heating and ventilation achieved in the building project or in the building in operation, the following energy saving classes (Table 7.3) are established in% of the deviation of the calculated specific characteristic of the heat energy consumption for heating and ventilation of the building from the normalized (base) value.

Design of buildings with energy saving class "D, E" is not allowed. Classes "A, B, C" are established for newly erected and reconstructed buildings at the stage of development of project documentation. Subsequently, during operation, the energy efficiency class of the building must be specified during an energy audit. In order to increase the share of buildings with classes "A, B", the subjects Russian Federation should apply economic incentives to both participants in the construction process and operating organizations.

Table 7.3

Energy saving classes of residential and public buildings

Class designation	Class name	Deviation value of the calculated (actual) value of the specific characteristic of the heat energy consumption for heating and ventilation of the building from the standard value, %	Recommended measures developed by the subjects of the Russian Federation
When designing and operating new and reconstructed buildings
A++	Very tall	Below -60
A+	From - 50 to - 60 inclusive
BUT	From - 40 to - 50 inclusive
B+	Tall	From - 30 to - 40 inclusive	Economic stimulus
AT	From - 15 to - 30 inclusive
C+	Normal	From - 5 to - 15 inclusive	Events are not developed
With	From + 5 to - 5 inclusive
with-	From + 15 to + 5 inclusive
D	Reduced	From + 15.1 to + 50 inclusive	Reconstruction with appropriate economic justification
E	Short	Over +50	Reconstruction with appropriate economic justification, or demolition

The calculated specific characteristic of the consumption of thermal energy for heating and ventilation of the building, W / (m 3 0 C), should be determined by the formula

k about - the specific heat-shielding characteristic of the building, W / (m 3 0 С), is determined as follows

, (7.3)

where is the actual total resistance to heat transfer for all layers of the fence (m 2 × ° C) / W;

The area of the corresponding fragment of the heat-shielding shell of the building, m 2;

V from - the heated volume of the building, equal to the volume limited by the internal surfaces of the external fences of buildings, m 3;

The coefficient that takes into account the difference between the internal or external temperature of the structure from those accepted in the calculation of the GSOP, =1.

k vent - specific ventilation characteristic of the building, W / (m 3 ·С);

k life - specific characteristic of household heat emissions of the building, W / (m 3 ·C);

k rad - specific characteristic of heat input into the building from solar radiation, W / (m 3 0 С);

ξ - coefficient taking into account the reduction in heat consumption of residential buildings, ξ = 0.1;

β - coefficient taking into account the additional heat consumption of the heating system, β h= 1,05;

ν - coefficient of heat transfer reduction due to thermal inertia of enclosing structures; recommended values are determined by the formula ν = 0.7+0.000025*(GSOP-1000);

The specific ventilation characteristic of the building, k vent, W / (m 3 0 С), should be determined by the formula

where c is the specific heat capacity of air, equal to 1 kJ / (kg ° C);

βv- coefficient of reduction of air volume in the building, βv = 0,85;

The average density of the supply air for the heating period, kg / m 3

353/, (7.5)

t from - the average temperature of the heating period, ° С, according to
, (see Appendix 6).

n in - average multiplicity air exchange of a public building for the heating period, h -1, for public buildings, according to, the average value of n in \u003d 2 is taken;

k e f - coefficient of efficiency of the heat exchanger, k e f =0.6.

The specific characteristic of the household heat emissions of the building, k life, W / (m 3 C), should be determined by the formula

, (7.6)

where q life - the value of household heat emissions per 1 m 2 of the area of \u200b\u200bresidential premises (A w) or the estimated area of \u200b\u200ba public building (A p), W / m 2, taken for:

a) residential buildings with an estimated occupancy of apartments less than 20 m 2 of total area per person q life = 17 W / m 2;

b) residential buildings with an estimated occupancy of apartments of 45 m 2 of total area or more per person q life = 10 W / m 2;

c) other residential buildings - depending on the estimated occupancy of the apartments by interpolation of the q life value between 17 and 10 W / m 2;

d) for public and administrative buildings household heat emissions are taken into account according to the estimated number of people (90 W / person) in the building, lighting (in terms of installed power) and office equipment (10 W / m 2), taking into account working hours per week;

t in, t from - the same as in formulas (2.1, 2.2);

A W - for residential buildings - the area of residential premises (A W), which include bedrooms, children's rooms, living rooms, offices, libraries, dining rooms, kitchen-dining rooms; for public and administrative buildings - the estimated area (A p), determined in accordance with SP 117.13330 as the sum of the areas of all premises, with the exception of corridors, vestibules, passages, staircases, elevator shafts, internal open stairs and ramps, as well as premises intended for placement engineering equipment and networks, m 2.

The specific characteristic of heat gains into the building from solar radiation, k p ad, W / (m 3 ° C), should be determined by the formula

, (7.7)

where - heat gains through windows and lanterns from solar radiation during the heating period, MJ / year, for four facades of buildings oriented in four directions, determined by the formula

Coefficients of relative penetration of solar radiation for light-transmitting fillings of windows and skylights, respectively, taken according to the passport data of the corresponding light-transmitting products; in the absence of data should be taken should be taken according to table (2.8); skylights with an angle of inclination of fillings to the horizon of 45 ° or more should be considered as vertical windows, with an angle of inclination of less than 45 ° - as skylights;

Coefficients that take into account the shading of the light opening, respectively, of windows and skylights by opaque filling elements, taken according to design data; in the absence of data, it should be taken from the table (2.8).

- the area of light openings of the facades of the building (the blind part of the balcony doors is excluded), respectively, oriented in four directions, m 2;

The area of light openings of the rooflights of the building, m;

The average value of the total solar radiation for the heating period (direct plus scattered) to vertical surfaces under actual cloudiness conditions, respectively oriented along the four facades of the building, MJ / m 2, is determined by adj. eight;

The average value of the total solar radiation for the heating period (direct plus scattered) to a horizontal surface under actual cloudiness conditions, MJ / m 2, is determined by adj. eight.

V from - the same as in the formula (7.3).

GSOP - the same as in formula (2.2).

Calculation of the specific characteristic of the consumption of thermal energy

for heating and ventilation of the building

Initial data

The calculation of the specific characteristic of the consumption of thermal energy for heating and ventilation of the building will be carried out using the example of a two-story individual residential building with total area 248.5 m 2. The values \u200b\u200bof the quantities required for the calculation: t c = 20 °С; t op = -4.1°C; = 3.28 (m 2 × ° C) / W; = 4.73 (m 2 × ° C) / W; = 4.84 (m 2 × ° C) / W; \u003d 0.74 (m 2 × ° C) / W; \u003d 0.55 (m 2 × ° C) / W; m 2; m 2; m 2; m 2; m 2; m 2; m 3; W / m 2; 0.7; 0; 0.5; 0; 7.425 m2; 4.8 m 2; 6.6 m 2; 12.375 m2; m 2; 695 MJ/(m 2 year); 1032 MJ / (m 2 year); 1032 MJ / (m 2 year); \u003d 1671 MJ / (m 2 year); \u003d \u003d 1331 MJ / (m 2 year).

Calculation procedure

1. Calculate the specific heat-shielding characteristic of the building, W / (m 3 0 С), according to the formula (7.3) is determined as follows

W / (m 3 0 C),

2. According to the formula (2.2), the degree-days of the heating period are calculated

D\u003d (20 + 4.1) × 200 \u003d 4820 ° С × day.

3. Find the coefficient of heat gain reduction due to the thermal inertia of the enclosing structures; recommended values are determined by the formula

ν \u003d 0.7 + 0.000025 * (4820-1000) \u003d 0.7955.

4. Find average density supply air for the heating period, kg / m 3, according to the formula (7.5)

353/=1.313 kg/m 3 .

5. We calculate the specific ventilation characteristic of the building according to the formula (7.4), W / (m 3 0 С)

W / (m 3 0 C)

6. I determine the specific characteristic of the household heat emissions of the building, W / (m 3 C), according to the formula (7.6)

W / (m 3 C),

7. According to the formula (7.8), heat gains through windows and lanterns from solar radiation during the heating period, MJ / year, are calculated for four facades of buildings oriented in four directions

8. According to the formula (7.7), the specific characteristic of heat gains into the building from solar radiation is determined, W / (m 3 ° С)

W / (m 3 ° С),

9. Determine the calculated specific characteristic of the consumption of thermal energy for heating and ventilation of the building, W / (m 3 0 С), according to the formula (7.2)

W / (m 3 0 C)

10. Compare the obtained value of the calculated specific characteristic of the consumption of thermal energy for heating and ventilation of the building with the normalized (base), W / (m 3 0 С), according to tables 7.1 and 7.2.

0.4 W / (m 3 0 C) \u003d 0.435 W / (m 3 0 C)

The calculated value of the specific characteristic of the consumption of thermal energy for heating and ventilation of the building must be less than the normalized value.

To assess the energy demand for heating and ventilation achieved in the building project or in the building in operation, the energy saving class of the designed residential building is determined by the percentage deviation of the calculated specific characteristic of the heat energy consumption for heating and ventilation of the building from the normalized (base) value.

Conclusion: The designed building belongs to the “C + Normal” energy saving class, which is set for newly erected and reconstructed buildings at the stage of development of project documentation. The development of additional measures to improve the energy efficiency class of the building is not required. Subsequently, during operation, the energy efficiency class of the building must be specified during an energy audit.

Security questions for section 7:

1. What is the main indicator of the consumption of thermal energy for heating and ventilation of a residential or public building at the stage of development of project documentation? What does it depend on?

2. What are the energy efficiency classes of residential and public buildings?

3. What energy saving classes are established for newly erected and reconstructed buildings at the stage of development of project documentation?

4. Designing buildings with which energy saving class is not allowed?

CONCLUSION

The problems of saving energy resources are especially important in the current period of development of our country. The cost of fuel and thermal energy is growing, and this trend is predicted for the future; at the same time, the volume of energy consumption is constantly and rapidly increasing. The energy intensity of the national income in our country is several times higher than in developed countries.

In this regard, the importance of identifying reserves to reduce energy costs is obvious. One of the ways to save energy resources is the implementation of energy-saving measures during the operation of heat supply, heating, ventilation and air conditioning (HVAC) systems. One of the solutions to this problem is to reduce the heat loss of buildings through the building envelope, i.e. reduction of thermal loads on DHW systems.

The importance of solving this problem is especially great in urban engineering, where only about 35% of all produced solid and gaseous fuels are spent on heat supply to residential and public buildings.

AT last years in cities, the imbalance in the development of sub-sectors of urban construction has sharply become apparent: the technical backwardness of the engineering infrastructure, the uneven development of individual systems and their elements, the departmental approach to the use of natural and produced resources, which leads to their irrational use and sometimes to the need to attract appropriate resources from other regions.

The need of cities for fuel and energy resources and the provision of engineering services is growing, which directly affects the increase in the incidence of the population, leads to the destruction of the forest belt of cities.

Application of modern thermal insulation materials with a high value of heat transfer resistance will lead to a significant reduction in energy costs, the result will be a significant economic effect in the operation of DHW systems through a reduction in fuel costs and, accordingly, an improvement in the environmental situation in the region, which will reduce the cost of medical care for the population.

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The processes of air movement inside the premises, its movement through fences and openings in fences, through channels and air ducts, air flow around the building and the interaction of the building with the surrounding air are combined general concept building air condition. In heating, the thermal regime of the building is considered. These two regimes, as well as the humidity regime, are closely related. Similar to the thermal regime, when considering the air regime of a building, three tasks are distinguished: internal, regional and external.

The internal task of the air regime includes the following issues:

a) calculation of the required air exchange in the room (determination of the amount of harmful emissions entering the premises, selection of the performance of local and general ventilation systems);

b) determination of the parameters of indoor air (temperature, humidity, speed of movement and content of harmful substances) and their distribution over the volume of premises at various options air supply and removal. Choice best options air supply and removal;

c) determination of air parameters (temperature and speed) in jet streams generated by supply ventilation;

d) calculation of the amount of harmful emissions escaping from under the shelters of local exhausts (diffusion of harmful emissions in the air stream and in rooms);

e) creation of normal conditions at workplaces (showering) or in separate parts of the premises (oases) by selecting the parameters of the supplied supply air.

The boundary task of the air regime unites the following questions:

a) determination of the amount of air passing through the external (infiltration and exfiltration) and internal (overflow) fences. Infiltration leads to an increase in heat loss of the premises. The greatest infiltration is observed in the lower floors of multi-storey buildings and in high industrial premises. Unorganized air flow between rooms leads to pollution clean rooms and distribution throughout the building unpleasant odors;

b) calculation of the areas of openings for aeration;

c) calculation of the dimensions of channels, air ducts, shafts and other elements of ventilation systems;

d) choice of air treatment method - giving it certain "conditions": for inflow - this is heating (cooling), humidification (drying), dust removal, ozonation; for the hood - this is cleaning from dust and harmful gases;

e) development of measures to protect the premises from the intrusion of cold outside air through open openings ( exterior doors, gates, technological openings). For protection, air and air-thermal curtains are usually used.

The external task of the air regime includes the following issues:

a) determination of the pressure created by the wind on the building and its individual elements (for example, a deflector, a lantern, facades, etc.);

b) calculation of the maximum possible amount of emissions that does not lead to pollution of the territory industrial enterprises; determination of the ventilation of the space near the building and between individual buildings on the industrial site;

c) selection of locations for air intakes and exhaust shafts of ventilation systems;

d) calculation and forecasting of atmospheric pollution harmful emissions; verification of the sufficiency of the degree of purification of the emitted polluted air.

main feature air regime buildings - the union of all premises and systems of the building into a single technological. system...

Legal mode air space is determined to some extent by the legal regime the area over which it is located.

Legal mode air the space of the Russian Federation is regulated by a large number of domestic acts ...

Thermal mode building. Thermal regime building is called...
...thermal and by air modes...

Legal mode air State space is determined by national legislation.

The logical basis of the ACS is the mathematical model of thermal and air modes building, implemented on a mini-computer.

Thermal and air modes buildings with the help of variable structural characteristics of the building are limited, so the main ...

§ 4. Mode flights in international air space. open air space is the space above the open sea and other territories with a special ...

Legal mode air...
Air Code of the Russian Federation establishes the principle of the carrier's responsibility to the passenger air vessel and cargo owner.

Aircurtains of periodic action are calculated so that its operation does not affect the thermal and air modes premises, i.e. so that the air taken in by V.z. from...

There are basic parameters of the air environment that determine the possibility of human existence in open areas and in dwellings. In particular, this is the concentration of various impurities in the air of the room, depending on the air, thermal and gas regimes of the building. Harmful impurities in the surface layer of the atmosphere can be in the form of aerosols, dust particles, various gaseous substances at the molecular level.

When spreading in the air under the action of coagulation or various chemical reactions harmful impurities may vary quantitatively and chemically. The gas regime of the building consists of three interconnected parts. The outer part is the processes of distribution of harmful impurities in the surface layer of the atmosphere with air currents washing the building and moving harmful substances.

The edge part is the process of penetration of harmful impurities into the building through cracks in the outer enclosing structures, open windows, doors, other openings and through mechanical ventilation systems, as well as the movement of impurities through the building. Inner part- the process of distribution of harmful impurities in the premises of the building (gas regimes of the premises).

For this, a multi-zone model of a ventilated room is used, on the basis of which the room is considered as a set of elementary volumes, the relationship and interaction between which occurs through the boundaries of elementary volumes. Within the framework of the gas regime of the building, the convective and diffusive transfer of harmful impurities is studied. The number of air ions in the air is characterized by their concentration in a cubic meter of air, and the air ion regime is part of the gas regime of the building.

Air ions are the smallest complexes of atoms or molecules that carry a positive or negative charge. Depending on the size and mobility, three groups of air ions are distinguished: light, medium and heavy. The reasons for air ionization are different: the presence of radioactive substances in the Earth's crust, the presence of radioactive elements in building and facing materials, natural radioactivity of both air and soil (radon and thoron) and rocks (isotopes K40, U238, Th232).

The main air ionizer is cosmic radiation, as well as water spraying, atmospheric electricity, friction of particles of sand, snow, etc. Air ionization occurs as follows: under the action of external factor a molecule or atom of a gas is given the energy necessary to remove one electron from the nucleus. The neutral atom becomes positively charged, and the resulting free electron joins one of the neutral atoms, transferring a negative charge to it, forming a negative air ion.

A certain number of molecules and gases that make up the air join such positively and negatively charged air ions in a fraction of a second. As a result, complexes of molecules are formed, called light air ions. Light air ions, colliding in the atmosphere with other air ions and condensation nuclei, form air ions of large sizes - medium air ions, heavy air ions, ultra-heavy air ions.

The mobility of air ions depends on the gas composition of air, temperature and atmospheric pressure. The size and mobility of positive and negative air ions depend on the relative humidity of the air - with an increase in humidity, the mobility of air ions decreases. The charge of an air ion is its main characteristic. If a light air ion loses its charge, then it disappears, and when a heavy or medium air ion loses its charge, such an air ion does not decay, and in the future it can acquire a charge of any sign.

The concentration of air ions is measured in the number of elementary charges in a cubic meter of air: e = +1.6 × 10-19 C/m3 (e/m3). Under the influence of ionization in the air, physical and chemical processes of excitation of the main components of air - oxygen and nitrogen - take place. The most stable negative air ions can form the following elements chemical substances and their compounds: carbon atoms, oxygen molecules, ozone, carbon dioxide, nitrogen dioxide, sulfur dioxide, water molecules, chlorine and others.

The chemical composition of light air ions depends on chemical composition air environment. This both affects the gas regime of the building and premises, and leads to an increase in the concentration of stable molecular air ions in the air. For harmful impurities, the norms of the maximum permissible concentration (MPC) are established, as for neutral uncharged molecules. The harmful effect of charged impurity molecules on the human body is increasing. The "contribution" of each type of molecular ions to the discomfort or comfort of the air environment surrounding a person is different.

How cleaner air, topics longer time life of light air ions, and vice versa - with air pollution, the life time of light air ions is small. Positive air ions are less mobile and live longer than negative air ions. Another factor characterizing the air-ionic regime of the building premises is the unipolarity coefficient, which shows the quantitative predominance of negative air ions over positive ones for any group of air ions.

For the surface layer of the atmosphere, the unipolarity coefficient is 1.1-1.2, showing the excess of the number of negative air ions over the number of positive ones. The unipolarity coefficient depends on the following factors: season, terrain, geographical location and the electrode effect from the influence of the negative charge of the Earth's surface, in which the positive direction of the electric field near the Earth's surface creates predominantly positive air ions.

In the case of the opposite direction of the electric field, negative air ions are predominantly formed. For a hygienic assessment of the air-ionic regime of a room, an indicator of air pollution was adopted, which is determined by the ratio of the sum of heavy air ions of positive and negative polarity to the sum of positive and negative light air ions. The lower the value of the air pollution index, the more favorable the air-ion regime.

The concentration of light air ions of both polarities significantly depends on the degree of urbanization of the area and on the ecological state of the human environment. Light air ions have a therapeutic and prophylactic effect on the human body at a concentration of 5 × 108-1.5 × 109 U/m3. In rural areas, the concentration of light air ions is within the normal range useful for humans.

In resorts and in mountainous areas, the concentration of light air ions is slightly higher than normal, but the beneficial effect remains, and in large cities on streets with heavy traffic, the concentration of light air ions is below normal and may approach zero. This clearly indicates the pollution of atmospheric air. Negative air ions are more sensitive to impurities than positive air ions.

Vegetation has a great influence on the aeroionic regime. Volatile plant secretions, called phytoncides, make it possible to qualitatively and quantitatively improve the aeroionic regime environment. In a pine forest, the concentration of light air ions increases and the concentration of heavy air ions decreases. Among the plants that can favorably affect the air-ionic regime, the following can be distinguished: snowdrop, lilac, white locust, geranium, oleander, Siberian spruce, fir.

Phytoncides affect the air-ionic regime by the processes of recharging air ions, due to which the transformation of medium and heavy air ions into lungs is possible. The ionization of the air is important for human health and well-being. Stay of people in a ventilated room with high humidity and dustiness of the air with insufficient air exchange significantly reduces the number of light air ions. At the same time, the concentration of heavy air ions increases, and the dust charged with ions is retained in the respiratory tract of a person by 40% more.

People often complain about lack fresh air, rapid fatigue, headaches, reduced attention and irritability. This is due to the fact that the parameters of thermal comfort are well studied, and the parameters of air comfort are not studied enough. The air being processed in the air conditioner, in the supply chamber, in the air heating system, almost completely loses air ions, and the air ion regime in the room deteriorates tenfold.

Light air ions have a therapeutic and prophylactic effect on the human body at a concentration of 5 × 108-1.5 × 109 U/m3. With artificial air ionization, the resulting light air ions have the same useful properties, as air ions formed in a natural way. In accordance with the standards, increased and decreased concentrations of light air ions in the air are classified as physically harmful factors.

There are several types of devices for artificial ionization of indoor air, among which ionizers of the following type can be distinguished: coronary, radioisotope, thermionic, hydrodynamic and photoelectric. Ionizers can be local and general, stationary and portable, adjustable and unregulated, generating unipolar and bipolar light air ions.

It is advantageous to combine air ionizers with supply ventilation and air conditioning systems, while it is necessary that the air ionizers be located as close as possible to the serviced area of the room in order to reduce the loss of air ions during their transportation. Air heating leads to an increase in the number of light air ions, but the interaction of air ions with the metal parts of heaters and air heaters reduces their concentration, air cooling leads to a noticeable decrease in the concentration of light air ions, drying and moistening leads to the destruction of all light mobile air ions and the formation of heavy air ions due to water spraying .

The use of plastic parts of ventilation and air conditioning systems can reduce the adsorption of light air ions and increase their concentration in the room. Heating favorably affects the increase in the concentration of light air ions in comparison with the concentration of light air ions in the outside air. The growth of light air ions during the operation of the heating system in winter is compensated by the decrease in these air ions as a result of human activity.

After the irrigation chamber, the decrease in light negative air ions based on the molecule of ozone, oxygen and nitrogen oxide occurs dozens of times, and instead of these air ions, water vapor air ions appear. In underground rooms with limited ventilation, the decrease in the amount of light negative air ions based on the ozone and oxygen molecule occurs hundreds of times, and on the basis of the nitric oxide molecule - up to 20 times.

From air conditioning systems, the concentration of heavy air ions increases slightly, and in the presence of people, the concentration of heavy air ions increases significantly. The balance of formation and destruction of light air ions can be characterized by the following significant circumstances: the entry of light air ions with the influx of outside air into the serviced premises (in the presence of light air ions outside), a change in the concentration of light air ions when air passes into the serviced premises (mechanical ventilation and air conditioning reduce the concentration of air ions) , a decrease in the concentration of light air ions at in large numbers people in the room, high dust content, gas burning, etc.

An increase in the concentration of light air ions occurs with good ventilation, the presence of phytoncide-forming plants, artificial air ionizers, good housing ecology, and successful measures to protect and improve the state of the environment in settlements. The nature of the change in the concentration of light positive and negative air ions in the surface layer of the atmosphere in the annual mode coincides with the fluctuations in the outdoor temperature, visibility in the atmosphere, and the duration of insolation of the territory in the annual mode.

From November to March, there is an increase in the concentration of heavy air ions and a decrease in the concentration of light air ions; in spring and summer, the number of all groups of heavy air ions decreases and the number of light air ions increases. In the daily mode, the concentration of light air ions is maximum in the evening and at night, when the air is clean - from eight in the evening to four in the morning, the concentration of light air ions is minimal from six in the morning to three in the afternoon.

Before a thunderstorm, the concentration of positive air ions increases, during a thunderstorm and after a thunderstorm, an increase in the number of negative air ions occurs. Near waterfalls, near the sea during the surf, near fountains and in other cases of spraying and spraying water, the number of light and heavy positive and negative air ions increases. Tobacco smoke worsens the air-ionic regime of the room, reducing the amount of light air ions.

In a room of about 40 m2 with poor ventilation, depending on the number of cigarettes smoked, the concentration of light air ions decreases. The respiratory tract and human skin are areas that perceive air ions. Most or less of the light and heavy air ions, when passing through the respiratory tract, give their charges to the walls of the air passage.

An increased level of light air ions leads to a reduction in morbidity and mortality, ionized air increases the body's resistance to diseases. In the presence of clean air ionized by light air ions, working capacity increases, the recovery of working capacity after prolonged loads is accelerated, and the body's resistance to toxic environmental influences increases.

To date, it is known that air ionization up to a value of 2 × 109-3 × 109 U/m3 has a favorable, normalizing effect on the human body. Higher concentrations - more than 50 × 109 U/cm3 of ionization - are unfavorable, the desired level is 5 × 108-3 × 109 U/m3. The efficiency of the air-ion regime is directly related to the fulfillment of air exchange standards. Ionized air must be dust-free and free of chemical pollution of various origins.

The processes of moving air inside the premises, its movement through fences and openings in fences, along channels and air ducts, the flow of air around the building and the interaction of the building with the surrounding air are united by the general concept of the air regime of the building. In heating, the thermal regime of a building is considered. These two regimes, as well as the humidity regime, are closely related to each other. Similar to the thermal regime, when considering the air regime of a building, three tasks are distinguished: internal, regional and external.

The internal task of the air regime includes the following issues:

b) determining the parameters of indoor air (temperature, humidity, speed and content of harmful substances) and their distribution over the volume of the premises with various options for supplying and removing air. Selection of optimal options for supply and removal of air;

c) determination of air parameters (temperature and velocity) in jet streams created by supply ventilation;

d) calculation of the amount of harmful emissions escaping from under the shelters of local exhausts (diffusion of harmful emissions in the air flow and in rooms);

e) creation of normal conditions at workplaces (showering) or in separate parts of the premises (oases) by selecting the parameters of the supplied supply air.

The boundary task of the air regime unites the following questions:

a) determination of the amount of air passing through the external (infiltration and exfiltration) and internal (overflow) enclosures. Infiltration leads to an increase in heat loss of the premises. The greatest infiltration is observed in the lower floors of multi-storey buildings and in high industrial premises. The unorganized flow of air between rooms leads to pollution of clean rooms and the spread of unpleasant odors throughout the building;

b) calculation of the areas of openings for aeration;

c) calculation of the dimensions of channels, air ducts, shafts and other elements of ventilation systems;

e) development of measures to protect the premises from the intrusion of cold outside air through open openings (external doors, gates, technological openings). For protection, air and air-thermal curtains are usually used.

The external task of the air regime includes the following issues:

a) determination of the pressure created by the wind on the building and its individual elements (for example, a deflector, a lantern, facades, etc.);

b) calculation of the maximum possible amount of emissions that does not lead to pollution of the territory of industrial enterprises; determination of the ventilation of the space near the building and between individual buildings on the industrial site;

c) selection of locations for air intakes and exhaust shafts of ventilation systems;

d) calculation and forecasting of atmospheric pollution by harmful emissions; verification of the adequacy of the degree of purification of polluted air emitted.

Principal solutions for ventilation ind. building.

42. Sound and noise, their nature, physical characteristics. Sources of noise in ventilation systems.

Noise - random fluctuations of various physical nature, characterized by the complexity of the temporal and spectral structure.

Initially, the word noise referred exclusively to sound vibrations, but in modern science it has been extended to other types of vibrations (radio, electricity).

Noise - a set of aperiodic sounds of varying intensity and frequency. From a physiological point of view, noise is any adverse perceived sound.

Noise classification. Noises consisting of a random combination of sounds are called statistical noises. Noises with a predominance of any tone, caught by ear, are called tonal.

Depending on the environment in which sound propagates, structural or hull and airborne noises. Structural noise occurs when an oscillating body is in direct contact with machine parts, pipelines, building structures etc. and propagate along them in the form of waves (longitudinal, transverse, or both at the same time). Vibrating surfaces transmit vibrations to air particles adjacent to them, forming sound waves. In cases where the source of noise is not associated with any structures, the noise emitted by it into the air is called airborne.

According to the nature of the occurrence, noise is conditionally divided into mechanical, aerodynamic and magnetic.

According to the nature of the change in the total intensity over time, the noise is divided into impulsive and stable. Impulse noise has a rapid rise in sound energy and a rapid fall, followed by a long break. For stable noise, the energy changes little over time.

According to the duration of action, noises are divided into long-term (total duration continuously or with pauses of at least 4 hours per shift) and short-term (duration less than 4 hours per shift).

Sound, in a broad sense, is elastic waves that propagate longitudinally in a medium and create mechanical vibrations in it; in a narrow sense - the subjective perception of these vibrations by special sense organs of animals or humans.

Like any wave, sound is characterized by amplitude and frequency spectrum. Usually a person hears sounds transmitted through the air in the frequency range from 16-20 Hz to 15-20 kHz. Sound below the human hearing range is called infrasound; higher: up to 1 GHz - by ultrasound, from 1 GHz - by hypersound. Among the audible sounds, phonetic, speech sounds and phonemes (of which oral speech consists) and musical sounds (of which music consists) should also be highlighted.

The source of noise and vibration in ventilation systems is the fan, in which non-stationary processes of air flow through the impeller and in the casing itself take place. These include speed pulsations, the formation and shedding of vortices from the fan elements. These factors are the cause of aerodynamic noise.

E.Ya. Yudin, who studied the noise of ventilation installations, points out three main components of the aerodynamic noise generated by the fan:

1) vortex noise - a consequence of the formation of vortices and their periodic disruption when air flows around the elements of the fan;

2) noise from local flow inhomogeneities formed at the inlet and outlet of the wheel and leading to unsteady flow around the blades and fixed elements of the fan located near the wheel;

3) rotational noise - each moving fan wheel blade is a source of air disturbance and vortex formation. The proportion of rotational noise in the total fan noise is usually negligible.

Vibrations of structural elements ventilation unit, often due to poor wheel balance, are the cause of mechanical noise. The mechanical noise of the fan usually has a shock character, an example of this is knocking in the gaps of worn bearings.

The dependence of noise on the circumferential speed of the impeller at various characteristics network for a centrifugal fan with forward-curved blades is shown in the figure. It follows from the figure that at a peripheral speed of more than 13 m/s, the mechanical noise of the ball bearings is "masked" by aerodynamic noise; at lower speeds, bearing noise dominates. At a peripheral speed of more than 13 m/s, the level of aerodynamic noise increases faster than the level of mechanical noise. Centrifugal fans with backward curved blades have a slightly lower level of aerodynamic noise than fans with forward curved blades.

In ventilation systems, in addition to the fan, noise sources can be vortices formed in the elements of the air ducts and in the ventilation grilles, as well as vibrations of insufficiently rigid walls of the air ducts. In addition, extraneous noise from neighboring rooms through which the air duct passes through the walls of the air ducts and ventilation grilles may penetrate.