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  Industrial ventilation And conditioning. Ventilation


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  Industrial ventilation And conditioning. Ventilation– indoor air exchange carried out using various systems and devices.


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  Industrial ventilation And conditioning. Ventilation– indoor air exchange carried out using various systems and devices.


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  Basic principles of economic-geographical research. Systematicity and complexity as principles of EG research. ... Industrial ventilation And conditioning …


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  Industrial ventilation And conditioning. Ventilation– exchange of air in rooms, carried out using various systems and devices.... more details ".


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  System requirements ventilation And conditioning
  ventilation equipment And air conditioners.


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  Mechanical ventilation used in buildings independent system air exchange or in combination with other systems (natural And conditioning).
  Sources of noise on industrial enterprises are very diverse.


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  For residential premises, air change (infiltration) can reach 0.5-0.75 volume per hour, for industrial 1.0-1.5 volumes per
  The disadvantage of mechanical ventilation is the noise it creates. Conditioning- artificial automatic processing...


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  System requirements ventilation And conditioning depend on the tasks for which these systems are installed.
  Vibration and sound insulation ventilation equipment And air conditioners.


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  Shapes and sizes industrial buildings are very diverse. In some cases they can contribute to better removal
  Heating systems and ventilation, often combined into a single heating- ventilation system or system conditioning air...

Similar pages found:10

MINISTRY OF EDUCATION AND SCIENCE OF UKRAINE

KRASNODON MINING TECHNIQUE

Abstract on the subject “SAFETY

TECHNOLOGICAL

PROCESSES AND PRODUCTION"

on the topic: “INDUSTRIAL VENTILATION »

Student of group 1EP-06

Uryupov Oleg

Checked by: Drokina T.M.

Krasnodon 2010

Ventilation is a complex of interconnected devices and processes for creating the required air exchange in production premises. The main purpose of ventilation is to remove working area contaminated or overheated air and supply clean air, as a result of which the necessary favorable conditions air environment. One of the main tasks that arises when installing ventilation is determining the air exchange, i.e. the amount ventilation air necessary to ensure an optimal sanitary and hygienic level of the indoor air environment.

Depending on the method of air movement in industrial premises, ventilation is divided into natural and artificial (mechanical).

The use of ventilation must be justified by calculations that take into account temperature, air humidity, release of harmful substances, and excess heat generation. If there are no harmful emissions in the room, then ventilation should provide an air exchange of at least 30 m3 / h for each worker (for rooms with a volume of up to 20 m3 per worker). When harmful substances are released into the air of the working area, the necessary air exchange is determined based on the conditions of their dilution to the maximum permissible concentration, and in the presence of thermal excess - from the conditions of maintaining permissible temperature in the work area.

Natural ventilation production premises is carried out due to the temperature difference in the room from the outside air (thermal pressure) or the action of wind (wind pressure). Natural ventilation can be organized or unorganized.

With unorganized natural ventilation air exchange is carried out by displacing internal thermal air with external cold air through windows, vents, transoms and doors. Organized natural ventilation, or aeration, provides air exchange in pre-calculated volumes and adjustable in accordance with meteorological conditions. Channelless aeration is carried out using openings in the walls and ceiling and is recommended in large rooms with significant excess heat. To obtain the calculated air exchange, ventilation openings in the walls, as well as in the roof of the building (aeration skylights) are equipped with transoms that open and close from the floor of the room. By manipulating the transoms, you can regulate the air exchange when changing outside temperature air or wind speed (Fig. 4.1). The area of ​​ventilation openings and skylights is calculated depending on the required air exchange.

Rice. 4.1. Scheme of natural ventilation of the building: A- when there is no wind; b- in the wind; 1 - exhaust and supply openings; 2 - fuel generating unit

In small production premises, as well as in premises located in multi-storey buildings industrial buildings, channel aeration is used, in which contaminated air is removed through ventilation ducts in the walls. To enhance the exhaust, deflectors are installed at the exit from the ducts on the roof of the building - devices that create draft when the wind blows on them. In this case, the wind flow, hitting the deflector and flowing around it, creates a vacuum around most of its perimeter, which ensures air suction from the channel. The most widely used deflectors are the TsAGI type (Fig. 4.2), which are a cylindrical shell mounted above the exhaust pipe. To improve air suction by wind pressure, the pipe ends in a smooth expansion - a diffuser. A cap is provided to prevent rain from entering the deflector.

Rice. 4.2. TsAGI type deflector diagram: 1 - diffuser; 2 - cone; 3 - legs holding the cap and shell; 4 - shell; 5 - cap

Calculation of the deflector comes down to determining the diameter of its pipe. Approximate diameter of the pipe d TsAGI type deflector can be calculated using the formula:

Where L- ventilation air volume, m3/h; - air speed in the pipe, m/s.

The air speed (m/s) in the pipe, taking into account only the pressure created by the action of the wind, is found using the formula

where is wind speed, m/s; - the sum of the local resistance coefficients of the exhaust air duct in its absence e = 0.5 (at the entrance to the branch pipe); l- length of the branch pipe or exhaust air duct, m.

Taking into account the pressure created by the wind and thermal pressure, the air speed in the nozzle is calculated using the formula

where is thermal pressure Pa; here is the height of the deflector, m; - density, respectively, of outdoor air and indoor air, kg/m3.

The speed of air movement in the pipe is approximately 0.2...0.4 wind speed, i.e. If the deflector is installed without exhaust pipe directly in the ceiling, then the air speed is slightly higher.

Aeration is used for ventilation of large industrial premises. Natural air exchange is carried out through windows, skylights using heat and wind pressure (Fig. 4.3). Thermal pressure, as a result of which air enters and leaves the room, is formed due to the temperature difference between the external and internal air and is regulated by varying degrees of opening of the transoms and lanterns. The difference between these pressures at the same level is called internal excess pressure. It can be both positive and negative.

Rice. 4.3. Building aeration scheme

At negative value(exceeding external pressure over internal) air enters the room, and when positive value(internal pressure exceeds external pressure) air leaves the room. At = 0 there will be no air movement through the holes in the outer fence. The neutral zone in the room (where = 0) can only exist under the influence of excess heat alone; when there is wind with excess heat, it sharply shifts upward and disappears. The distances of the neutral zone from the middle of the exhaust and supply openings are inversely proportional to the squares of the areas of the openings. At, where are the areas, respectively, of the inlet and outlet openings, m2; -height of the level of equal pressures, respectively, from the inlet to the outlet, m.

Air flow G, which flows through a hole having an area F, calculated by the formula:

Where G- massive second consumption air, t/s; m is the flow coefficient depending on the outflow conditions; r - air density in the initial state, kg/m3; - pressure difference inside and outside the room in a given hole, Pa.

The approximate amount of air leaving the room through 1 m2 of opening area, taking into account only thermal pressure and provided that the areas of the holes in the walls and lanterns are equal and the flow coefficient m = 0.6, can be determined using a simplified formula:

Where L- amount of air, m3/h; N- distance between the centers of the lower and upper holes, m; - temperature difference: average (altitude) indoors and outdoor, ° C.

Aeration using wind pressure is based on the fact that excess pressure occurs on the windward surfaces of the building, and rarefaction occurs on the windward sides. Wind pressure on the surface of the fence is found by the formula:

Where k- aerodynamic coefficient, showing what proportion of the dynamic wind pressure is converted into pressure in a given section of the fence or roof. This coefficient can be taken on average equal to + 0.6 for the windward side, and -0.3 for the leeward side.

Natural ventilation is cheap and easy to operate. Its main disadvantage is that the supply air is introduced into the room without preliminary cleaning and heating, and the exhaust air is not cleaned and pollutes the atmosphere. Natural ventilation is applicable where there are no large emissions of harmful substances into the work area.

Artificial (mechanical) ventilation eliminates the shortcomings of natural ventilation. With mechanical ventilation, air exchange is carried out due to the air pressure created by fans (axial and centrifugal); air in winter time It is heated, cooled in the summer and, in addition, cleaned of contaminants (dust and harmful vapors and gases). Mechanical ventilation can be supply, exhaust, supply and exhaust, and according to the place of action - general and local.

At supply ventilation system(Fig. 4.4, A) air is taken from the outside using a fan through a heater, where the air is heated and, if necessary, humidified, and then supplied to the room. The amount of air supplied is controlled by valves or dampers installed in the branches. Polluted air comes out unpurified through doors, windows, lanterns and cracks.

At exhaust ventilation system(Fig. 4.4, b) polluted and overheated air is removed from the room through a network of air ducts using a fan. Polluted air is cleaned before being released into the atmosphere. Clean air is sucked in through windows, doors, and structural leaks.

Supply and exhaust ventilation system(Fig. 4.4, V) consists of two separate systems - supply and exhaust, which simultaneously supply clean air into the room and remove polluted air from it. Supply systems ventilation also replaces the air removed by local suction and spent on technological needs: fire processes, compressor units, pneumatic transport, etc.

To determine the required air exchange, it is necessary to have the following initial data: the amount of harmful emissions (heat, moisture, gases and vapors) per 1 hour, the maximum permissible amount (MAC) of harmful substances in 1 m3 of air supplied to the room.

Rice. 4.4. Scheme of supply, exhaust and supply and exhaust mechanical ventilation: A- supply; 6 - exhaust; V- supply and exhaust; 1 - air intake for intake of clean air; 2 - air ducts; 3 - filter for air purification from dust; 4 - air heaters; 5 - fans; 6 - air distribution devices (nozzles); 7 - exhaust pipes for releasing exhaust air into the atmosphere; 8 - devices for cleaning exhaust air; 9 - air intake openings for exhaust air; 10 - valves for regulating the amount of fresh secondary recirculation and exhaust air; 11 - a room served by supply and exhaust ventilation; 12 - air duct for the recirculation system

For rooms with the release of harmful substances, the required air exchange L, m3 / h, is determined from the condition of the balance of harmful substances entering it and diluting them to acceptable concentrations. Balance conditions are expressed by the formula:

Where G- rate of release of harmful substances from technological installation, mg/h; G etc- rate of entry of harmful substances with air flow into the work area, mg/h; Gud- the rate of removal of harmful substances diluted to permissible concentrations from the work area, mg/h.

Replacing in expression G etc And Gud by the product and, where and are, respectively, the concentration (mg/m3) of harmful substances in the supply and removed air, a and the volume of supply and removed air in m3 per 1 hour, we obtain

To maintain normal pressure in the working area, equality must be satisfied, then

The necessary air exchange, based on the content of water vapor in the air, is determined by the formula:

where is the amount of removed or supply air indoors, m3/h; G P- mass of water vapor released in the room, g/h; - moisture content of removed air, g/kg, dry air; - moisture content of supply air, g/kg, dry air; r - density of supply air, kg/m3.

where are the masses (g) of water vapor and dry air, respectively. It must be borne in mind that the values ​​and are taken from the tables physical characteristics air depending on the value of the standardized relative humidity of the exhaust air.

To determine the volume of ventilation air based on excess heat, it is necessary to know the amount of heat entering the room from various sources(heat arrival), and the amount of heat spent to compensate for losses through the building’s enclosures and other purposes, the difference expresses the amount of heat that goes to heat the air in the room and which must be taken into account when calculating air exchange.

The air exchange required to remove excess heat is calculated using the formula:

where is the excess amount of heat, J/s, is the temperature of the removed air, ° K; - supply air temperature, ° K; WITH- specific heat capacity of air, J/(kg×K); r - air density at 293° K, kg/m3.

Local ventilation Is there an exhaust or supply? Exhaust ventilation are suitable when pollution can be captured directly at the point of its origin. For this purpose, fume hoods, umbrellas, curtains, side suction at bathtubs, casings, suction at machine tools, etc. are used. Supply ventilation includes air showers, curtains, and oases.

Fume hoods work with natural or mechanical exhaust. To remove excess heat from a cabinet or harmful impurities naturally requires the presence of a lifting force, which occurs when the temperature of the air in the cabinet exceeds the temperature of the air in the room. The exhaust air must have sufficient energy to overcome aerodynamic resistance on the way from the entrance to the cabinet to the point of release into the atmosphere.

Volume flow rate of air removed from fume hood with natural exhaust (Fig. 4.5), (m3 / h)

Where h- height of the open cabinet opening, m; Q- amount of heat generated in the cabinet, kcal/h; F- area of ​​the open (working) opening of the cabinet, m2.

Rice. 4.5. Scheme of a fume hood with natural exhaust: 1 - level zero pressure; 2 - diagram of pressure distribution in the working hole; T1- room air temperature; T 2 - gas temperature inside the cabinet

Required exhaust pipe height (m)

where is the sum of all resistances of a straight pipe along the path of air movement; d- straight pipe diameter, m (preset).

With mechanical extraction

Where v- average suction speed in sections of an open opening, m/s.

Onboard suctions arranged near production baths for removal of harmful vapors and gases that are released from bath solutions. For bath widths up to 0.7 m, single-sided suction units are installed on one of its longitudinal sides. When the bath width is more than 0.7 m (up to 1 m), double-sided suction is used (Fig. 4.6).

The volumetric flow rate of air sucked from hot baths by single- and double-sided suction units is found using the formula:

Where L- volumetric air flow, m3/h, k 3 - safety factor equal to 1.5...1.75, for baths with special harmful solutions 1,75...2; k T- coefficient for taking into account air leaks from the ends of the bath, depending on the ratio of the width of the bath IN to its length l; for single-sided simple suction; for double-sided - ; WITH- dimensionless characteristic equal to 0.35 for single-sided suction and 0.5 for double-sided suction; j is the angle between the suction boundaries (Fig. 4.7); (in calculations it has a value of 3.14); TV And Tp- absolute temperatures, respectively, in the bath and air in the room, °K; g=9.81 m/s2.

Exhaust hoods used when the released harmful vapors and gases are lighter than the surrounding air and its mobility in the room is insignificant. Umbrellas can be either with natural or mechanical exhaust.

Rice. 4.6. Double-sided bath suction

With natural exhaust the initial volumetric air flow rate in the thermal jet rising above the source is determined by the formula:

Where Q- amount of convective heat, W; F- horizontal projection area of ​​the heat source surface, m2; N- distance from the heat source to the edge of the umbrella, m.

With mechanical extraction the aerodynamic characteristic of the umbrella includes the speed along the axis of the umbrella, which depends on the angle of its opening; with increasing opening angle, the axial speed increases compared to the average. At an opening angle of 90°, the axial speed is l.65 v (v- average speed, m/s), with an opening angle of 60°, the speed along the axis and across the entire cross section is equal v .

In general, the flow rate of air removed by the umbrella is

Where v- average speed of air movement in the intake opening of the umbrella, m/s; when removing heat and moisture, the speed can be taken as 0.15...0.25 m/s; F- design cross-sectional area of ​​the umbrella, m2.

The receiving hole of the umbrella is located above the heat source; it must correspond to the configuration of the umbrella, and the dimensions are somewhat larger than the dimensions of the heat source in plan. Umbrellas are installed at a height of 1.7...1.9 m above the floor.

To remove dust from various machines, dust collection devices are used in the form of protective and dust removal casings, funnels, etc.

Rice. 4.7. The angle between the boundaries of the suction torch at different locations baths: A- near the wall (); b- next to the bathroom without suction (); V- separately (); 1 - bath with suction; 2 - bath without suction.

In calculations, take p = 3.14

Volumetric air flow L(m3/h) removed from grinding, grinding and roughening machines is calculated depending on the diameter of the wheel d To p(mm), namely:

at< 250 мм L = 2,

at 250...600 mm L = 1,8 ;

at > 600 mm L = 1,6.

The air flow rate (m3/h) removed by the funnel is determined by the formula:

Where VH- initial speed of the exhaust torch (m/s), equal to speed transportation of dust in the air duct, accepted for heavy emery dust 14...16 m/s and for light mineral dust 10...12 m/s; l- working length of the exhaust torch, m; k- coefficient depending on the shape and aspect ratio of the funnel: for a round hole k= 7.7 for rectangular with aspect ratio from 1:1 to 1:3 k = 9,1; V k- the required final speed of the exhaust torch at the circle, taken equal to 2 m/s.

LITERATURE

1. Life safety/Ed. Rusaka O.N.-S.-Pb.: LTA, 1996.

2. Belov S.V. Life safety is the science of survival in the technosphere. NMS materials on the discipline “Life Safety”. - M.: MSTU, 1996.

3. All-Russian monitoring of the social and labor sphere 1995. Statistical collection. - Ministry of Labor of the Russian Federation, M.: 1996.

4. Environmental hygiene./Ed. Sidorenko G.I..- M.: Medicine, 1985.

5. Occupational hygiene when exposed to electromagnetic fields./Ed. Kovshilo V.E.- M.: Medicine, 1983.

6. Zolotnitsky N.D., Pcheliniev V.A.. Occupational safety in construction. - M.: Higher School, 1978.

7. Kukin P.P., Lapin V.L., Popov V.M., Marchevsky L.E., Serdyuk N.I. Fundamentals of radiation safety in human life. - Kursk, KSTU, 1995.

8. Lapin V.L., Popov V.M., Ryzhkov F.N., Tomakov V.I. Safe human interaction with technical systems. - Kursk, KSTU, 1995.

9. Lapin V.L., Serdyuk N.I. Occupational safety in foundry production. M.: Mechanical Engineering, 1989.

10. Lapin V.L., Serdyuk N.I. Occupational safety management at an enterprise. - M.: MIGZH MATI, 1986.

11. Levochkin N.N. Engineering calculations on labor protection. Publishing house of Krasnoyarsk University, -1986.

12. Occupational safety in mechanical engineering./Ed. Yudina B.Ya., Belova S.V. M.: Mechanical Engineering, 1983.

13. Labor protection. Information and analytical bulletin. Vol. 5.- M.: Ministry of Labor of the Russian Federation, 1996.

14. Putin V.A., Sidorov A.I., Khashkovsky A.V. Occupational safety, part 1. - Chelyabinsk, ChTU, 1983.

15. Rakhmanov B.N., Chistov E.D. Safety during operation of laser installations. - M.: Mashinostroenie, 1981.

16. Saborno R.V., Seledtsov V.F., Pechkovsky V.I. Electrical safety at work. Methodological instructions. - Kyiv: Vishcha School, 1978.

17. Reference book on labor protection/Ed. Rusaka O.N., Shaidorova A.A.- Chisinau, Publishing House “Cartea Moldovenasca”, 1978.

18. Belov S.V., Kozyakov A.F., Partolin O.F. and others. Means of protection in mechanical engineering. Calculation and design. Directory/Ed. Belova S.V.-M.: Mechanical Engineering, 1989.

19. Titova G.N. Toxicity of chemicals. - L.: LTI, 1983.

20. Tolokontsev N.A. Fundamentals of general industrial toxicology. - M.: Medicine, 1978.

21. Yurtov E.V., Leikin Yu.L. Chemical toxicology. - M.: MHTI, 1989.

Life safety Viktor Sergeevich Alekseev

25. Industrial ventilation and conditioning

Ventilation– indoor air exchange carried out using various systems and devices.

As a person stays indoors, the air quality in the room deteriorates. Along with exhaled carbon dioxide, other metabolic products, dust, and harmful industrial substances accumulate in the air. In addition, the temperature and humidity rise. Therefore, there is a need for room ventilation, which ensures air exchange– removing polluted air and replacing it with clean air.

Air exchange can be carried out naturally - through vents and transoms.

The best method of air exchange is artificial ventilation, in which fresh air is supplied and polluted air is removed mechanically - using fans and other devices.

The most advanced form of artificial ventilation is air conditioning- creation and maintenance in closed spaces and transport with the help of technical means the most favorable (comfortable) conditions for people, to ensure technological processes, the operation of equipment and devices, and the preservation of cultural and artistic values.

Air conditioning is achieved by creating optimal parameters of the air environment, its temperature, relative humidity, gas composition, air speed and air pressure.

Air conditioning units are equipped with devices for cleaning air from dust, for heating, cooling, drying and humidifying it, as well as for automatic regulation, control and management. In some cases, with the help of air conditioning systems, it is also possible to carry out odorization (saturation of air with aromatic substances), deodorization (neutralization of unpleasant odors), regulation of ionic composition (ionization), removal of excess carbon dioxide, oxygen enrichment and bacteriological air purification (in medical institutions where there are patients with airborne infection).

There are central air conditioning systems, which usually serve the entire building, and local air conditioning systems, which serve one room.

Air conditioning is carried out using air conditioners of various types, the design and arrangement of which depend on their purpose. Various devices are used for air conditioning: fans, humidifiers, air ionizers. In the premises, the optimal air temperature in winter is from + 19 to +21 C, in summer – from +22 to +25 C with a relative air humidity of 60 to 40% and an air speed of no more than 30 cm/s.

55. Artificial ventilation Artificial ventilation (ALV) provides gas exchange between the surrounding air (or a certain mixture of gases) and the alveoli of the lungs, is used as a means of resuscitation in case of sudden cessation of breathing, as a component