Microclimate and its influence on the human body Microclimate is a set of environmental parameters that affect the thermal sensations of a person: temperature, humidity and air velocity and intensity of thermal radiation from surrounding surfaces characteristic of a particular room. Heat exchange between the human body and the environment is carried out using the following processes: heat transfer - thermal conductivity through clothing QT; convection QK; thermal radiation into the surrounding space QELS; sweat moisture evaporation with...

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Page 51

Lab #4

STUDY WORKPLACE MICROCLIMATE

Goal of the work: get an idea aboutthe main parameters of the microclimate; to study the principles of rationing the microclimate in the premises; research and evaluate the parameters of the microclimate in the workplace.

Theoretical part

1. Microclimate and its impact on the human body

Microclimate this is a set of environmental parameters that affect the thermal sensations of a person: temperature, humidity and air velocity and the intensity of thermal radiation from surrounding surfaces, characteristic of a particular room.

The microclimate has a significant impact on the performance of a person, his well-being and health.

The need to take into account the parameters of the microclimate is predetermined by the conditions of the heat balance between the human body and the environment of the premises.

Man is constantly in the process of thermal interaction with the environment. The amount of heat generated by the human body Q depends on the degree of physical stress and microclimate parameters. In order for the physiological processes in his body to proceed normally, the heat released by the body must be completely removed into the human environment. Normal thermal sensations correspond to the equality between the amounts excreted by the human body and given into environment heat.

Heat exchange between the human body and the environment is carried out using the following processes:

• heat transfer (thermal conduction) through clothing Q T ;
• convection Q K ;
• thermal radiation to the environment Q ISL ;
• evaporation of moisture (sweat) from the surface of the skin Q ISP ;
• breathing (heating the inhaled air) Q D .

Heat transfer (thermal conductivity)consists in the transfer of heat from one particle to another by direct contact.

Convection is a process of heat exchange between the human body and the environment, carried out by moving air. Convective heat transfer depends on the ambient temperature, air velocity, air humidity and barometric pressure.

thermal radiationrepresentsheat exchange process carried out by emitting infrared electromagnetic waves. Thermal rays directly do not heat the air, but are well absorbed by solids and, therefore, heat them. heating up solid bodies they themselves become sources of heat and already by convection heat the air.

At an ambient temperature equal to or higher than the temperature of the surface of the human body, heat transfer occurs only in the form of sweat, for evaporation 1 g of which is spent about 0,6 kcal. At rest at an ambient temperature of 18 ° C, the proportion Q K is about 30 % of all heat removed, Q ISL  45%, Q ISP  20% and Q D  5%.

When the air temperature, its speed of movement and humidity change, when there are heated surfaces near a person, in conditions of physical work, etc. these ratios change significantly. So, at high temperatures (30 °C and above), especially when performing hard physical work, sweating can increase tenfold and reach 1 1.5L/h.

Normal thermal well-being of a person ( comfortable conditions corresponding to this type of activity) is provided if the heat balance condition is met:

Q H \u003d Q T + Q K + Q ISL + Q ISP + Q D,

where Q h the amount of heat generated by the human body.

Temperature internal organs of a person is maintained constant at a level of about 36,6 °C. This ability human body maintaining a constant temperature when changing microclimate parameters and when performing work of varying severity is called thermoregulation. If the thermal equilibrium is disturbed (for example, heat transfer is less than heat release), then heat is accumulated in the body – overheat. If heat transfer is greater than heat release, then hypothermia of the body occurs.

Comfortable weather conditions are an important factor ensuring high labor productivity and disease prevention. If the hygienic norms of the microclimate are not observed, the working capacity of a person decreases, the risk of injuries and a number of diseases, including occupational ones, increases.

2. The main parameters of the microclimate

Air humidity. Humidity characterizes the degree of its saturation with water vapor. The same air temperature, depending on the degree of its humidity, is felt by a person in different ways. Distinguish between absolute and relative humidity.

Absolute humidity(R ABS ) is the amount of water vapor contained in 1 m 3 air, i.e. vapor density (g/m 3 ). Absolute humidity is also characterized by water vapor pressure (hPa), i.e., the partial pressure that water vapor would exert on the walls of a vessel if all other air components were removed from this vessel.

Air with a limiting water vapor content at a given temperature is characterized by saturated vapor pressure ( P US ), which increases with increasingair temperature. After reaching R US water vapor starts to condense.

Absolute humidity by itself does not indicate whether water vapor is saturated or unsaturated, so the concept of relative humidity is introduced.

Relative Humidity (φ ) is determined by the expression:

φ \u003d (P ABS / P US ) 100,%. (1)

Relative humidity affects human heat transfer, for example, the rate of evaporation of moisture from the surface of the skin.

Air temperaturehas a great impact on the state of the human body. High ambient temperatures increase fatigue, can lead to overheating of the body or cause heat stroke. With a slight overheating, there is a slight increase in human body temperature, profuse sweating, a feeling of thirst appears, breathing and pulse become more frequent. In more severe conditions, heat stroke can occur, accompanied by an increase in temperature to 40 41 ° C, a weak and rapid pulse, and loss of consciousness. A characteristic sign of the onset of heat stroke is the almost complete cessation of sweating. Heat stroke can be fatal. Low ambient temperature can cause local or general hypothermia of the human body, cause colds or frostbite.

Air speedIt has great importance to create favorable living conditions. At a high air velocity, the intensity of convective heat transfer increases. If the air flows have a temperature below the temperature of the skin surface (30 - 33 ° C), they have a refreshing effect on the human body, and at temperatures above 37 °C are depressing. The human body begins to feel air currents at a speed of about 0.15 m/s.

thermal radiationfrom heated surfaces plays an important role in creating unfavorable microclimatic conditions. The action of radiant heat is not limited to changes occurring on the irradiated area of ​​the skin, – The entire body responds to radiation.In the body there are biochemical changes, disorders in the cardiovascular and nervous systems. With prolonged exposure to infrared rays, cataracts of the eyes (clouding of the lens) may occur.

Thermal sensations of a person depend on a combination of microclimatic parameters and on the intensity of physical work.

To assess the complex effect of microclimate parameters on the human body at low energy costs, the method of equivalent effective temperatures is used. This method makes it possible, on the basis of data on microclimate parameters, to judge the thermal state of a person. For its use, the conceptequivalent effective temperature(EET ), which characterizes the thermal sensation of a person under the simultaneous influence of temperature, humidity and air velocity. EET is estimated by the temperature of still air 100 % -th relative humidity, at which the thermal sensation of a person is the same as for a given combination of temperature, humidity and air velocity.

EET area in the temperature range from 17 to 22 °С corresponds to comfort zone , within which it is possible to distinguish the line of comfort corresponding to EET = 19 °C, at which almost all the studied people experience a feeling of comfort.

The figure shows a nomogram that allows you to determine the influence of microclimate parameters on a person's thermal sensation.

3. Rationing of microclimate parameters

The normalized parameters of the microclimate in industrial premises are: air temperature; relative humidity; air speed; the temperature of the room surfaces (walls, ceiling, floor) and technological equipment; intensity of thermal radiation. When normalizing microclimate parameters, the intensity of energy consumption of workers (the category of work according to severity), the period of the year, and the time spent at the workplace are taken into account.

A distinction is made between optimal and acceptable microclimatic conditions.

Optimal microclimatic conditionsrepresent such combinations of microclimate parameters that provide a feeling of thermal comfort for an 8-hour work shift at a minimum voltage of thermoregulation mechanisms

Permissible microclimatic conditionscan lead to a feeling of thermal discomfort, tension in the mechanisms of thermoregulation, deterioration in well-being and performance. Under the condition of an 8-hour work shift, they do not cause damage or health problems. Permissible values ​​of microclimate parameters are set in cases where, due to technological requirements, technical and economically justified reasons, optimal values ​​\u200b\u200bcannot be provided.

Nomogram of Equivalent Effective Temperatures

Depending on the energy consumption per unit of time, work is divided into the following categories.

• light physical work(category I) activities with intensity of energy consumption up to 174 W.

Category I a includes work performed while sitting and accompanied by slight physical stress with an intensity of energy consumption up to 139 W.

Category I b include work performed while sitting, standing or walking and accompanied by some physical stress with an intensity of energy consumption 140 174 W.

• Physical work of moderate severity(category II ) activities with intensity of energy consumption 175 290 W.

Category IIa include work associated with constant walking, moving small (up to 1 kg) products or objects in a standing or sitting position and requiring a certain physical stress with an intensity of energy consumption 175 232 W .

Category II b includes work related to walking, moving and carrying heavy loads up to 10 kg and accompanied by moderate physical stress with intensity of energy consumption 233 290 W .

• Heavy physical work(category III ) activities with intensity of energy consumption with energy consumption over 290 Tue These works are associated with constant movement, moving and carrying significant (over 10 kg) heavy and requiring great physical effort.

When normalizing, two periods of the year are distinguished: cold (with average daily outdoor temperature+10 °C and below) and warm (with an average daily outdoor temperature above +10 °С).

In table. 1 the optimal ones are given (in brackets – permissible) values ​​of microclimate parameters at permanent workplaces of industrial premises.

The intensity of thermal exposure is taken into account if there are heat sources in the production room heated to a high temperature.

Table 1

Optimal (permissible) microclimate parameters

Period of the year	work	Temperature, °С	Relative humidity, %	Air speed, m/ c	Surface temperature, °С
Cold		22 24 (2 0 2 5 )	40 60 (15 - 75)		21-25 (19-26)
			21 23 (1924)	40 60 (15 - 75)	(0,2)	20-24 (18-25)
		IIa	1 9 2 1 (1723)	40 60 (15 - 75)	(0,3)	18-22 (16-24)
		IIb	17 19 (15 2 2 )	40 60 (15 - 75)	(0,4)	16-20 (14-23)
			16 18 (13 21 )	40 60 (15 - 75)	(0, 4 )	15-19 (12-22)
	Warm		23 25 (2 1 28)	4060 (15 - 75)	(0,2)	22-26 (20-29)
			22 24 (2 0 28)	4060 (15 - 75)	0, 1 (0,3)	21-25 (19-29)
		IIa	2 0 2 2 (18 27)	4060 (15 - 75)	0, 2 (0,4)	19-23 (17-28)
		IIb	19 2 1 (1627)	4060 (15 - 75)	0, 2 (0,5)	18-22 (15-28)
			18 20 (15 26)	4060 (15 - 75)	0, 3 (0, 5 )	17-21 (14-27)

4. Devices for studying microclimate parameters

Requirements for the organization of control and methods for measuring microclimate parameters are given in SanPiN. The following devices can be used for this.

thermometers are used to measure the temperature of air and surfaces. They can be liquid (mercury and alcohol) and electronic. Depending on the functions performed, there are ordinary, maximum, minimum and steam liquid thermometers.

Maximum thermometer(mercury) is used to determine highest temperature, which was indoors between the observation periods. This thermometer has a narrowing of the capillary at the point of its articulation with the reservoir. Here, the column of mercury, which has risen with an increase in temperature, during the subsequent cooling of the air, breaks away from the total mass of mercury in the tank and, thus, remains fixed at the achieved scale level. For subsequent measurements, the thermometer must be placed with the tank down and shaken vigorously to push the mercury out of the capillary until it combines with the mercury in the tank.

Minimum thermometer(alcohol) is used to fix the lowest temperature that was in the room between the periods of observation. The minimum thermometer has a freely moving glass pin inside the capillary. Before measuring the temperature, the thermometer is turned upside down with the tank, and the pin, under the action of gravity, falls to the end of the alcohol column. (its further movement is prevented by a surface film limiting the meniscus), then the thermometer is placed horizontally. As the temperature decreases and the column of alcohol shortens, the pin will be entrained by the alcohol, and as the temperature rises, the alcohol flows freely around it. Thus, the minimum temperature can be judged from the face of the pin facing the alcohol meniscus.

Pair thermometerIt is used to measure the air temperature in rooms with sources of significant thermal radiation. When measuring the temperature in such rooms, the readings of conventional types of thermometers may not correspond to the true air temperature, since they show the temperature of the surface of the thermometer itself, heated by thermal radiation. A paired thermometer consists of two thermometers, one of which has a silver-plated tank with alcohol, and the other is blackened. Therefore, one reflects the bulk of the radiant heat, while the other absorbs it. In this case, the true air temperature is determined by the formula:

t HEAT = t B K(t H t B ) , (2)

where t B indications of a "brilliant" thermometer;

t H readings of the "black" thermometer;

K calibration factor determined by the factory.

Electronic thermometersuse Various types temperature sensors. They allow you to speed up and automate the measurement process, get the result in digital form, and can be interfaced with a PC.

Psychrometers and hygrometers used to determine the humidity of the air. The most common in measuring the relative humidity of the air in the workplace are August and Assmann psychrometers, hair and electronic hygrometers.

August psychrometerconsists of two identical mercury thermometers with a division value up to 0,2 °C, mounted side by side on a tripod. The reservoir of one of the thermometers is wrapped in gauze or cambric soaked in distilled water. From the working surface of a wetted ("wet") thermometer, water evaporates the more, the drier the air, and the more it cools it. Therefore, the wet bulb reading is always lower than the dry bulb reading (except when the relative humidity is100% and the readings of both thermometers are the same).

Relative humidity when measured by the August psychrometer is determined by the formula:

φ = [ P SAT.V α (t C t V ) P ATM ] 100/ P SAT.S , %, (3)

where P US.V saturated steam pressure at the temperature of the “wet” thermometer (Table 2) , hPa ;

P US.C saturated vapor pressure at dry-bulb temperature (Table 2), hPa;

P ATM atmospheric (barometric pressure), hPa.

t C “dry” thermometer readings, °С;

t B “wet” thermometer readings, °С;

α – psychrometric coefficient depending on air velocity (Table 3).

Table 2

Pressure and density of saturated water vapor

at various temperatures

t, °С	Pressure rich steam, hPa	Density saturated p apa, g / m 3	t, °С	Pressure rich steam, hPa	Density of saturated p apa, g / m 3
	4,01	3 ,2 4		23,3 8	17, 3
	6,10	4 ,84		24, 86	1 8 ,3
	8,27	6, 8 4		26,43	19.4
	10, 7 3	8,30		28,0 8	20,0
	12,28			29, 83	21. 8
	l3.12	10,0		31.67	23,0
	14,02	10,7		33.60	24.4
	14,97	11.4		3 5 .64	25.8
	15,98	12,1		3 7,79	27,2
	17, 05	12, 8		40,04	28.7
	I8.17	13,6		42.42	30,3
	19,37	14,5		73,74	5l.2
	20,63	15,4		123.30	83 , 0
	21,97	16,3		1013

Table 3

Psychrometric coefficient

Air speed, m/s	0,13	0,16	0,20	0,40	0. 80
	0,00098	0,00090	0 ,00083	0 ,0006 8	0.00060	0.000 5 3

Note. For enclosed spaces without ventilationα = 0.00083 .

Assmann's psychrometer.The disadvantage of the August psychrometer is the variability in the speed of air movement around the wet bulb reservoir, caused by local air currents, drafts, and the movement of people.This disadvantage is not present in the aspirationAssmann psychrometer. In this devicethe reservoirs of both thermometers are placed in double brass tubes through which the test air is evenly sucked by means of a small clockwork fan. This arrangement of the psychrometer protects the thermometer reservoirs from radiant heat and guarantees a constant air velocity around the thermometers. In addition, due to the suction of a significant mass of air, the readings of this device are more accurate than the August psychrometer, which determines the humidity of the air in the immediate vicinity of the device.

Before operation, the reservoir of the right thermometer, wrapped in cambric, is moistened with distilled water, the fan spring is started, and through 4 minutes readings are taken from thermometers. Relative humidity is determined by the formula (%):

φ \u003d P SAT.V 0.497 10 -3 (t C t V ) P ATM 100/ P SAT.S (4)

Household psychrometers(for example, PBU-1) are similar to August's psychrometer. They are used for a quick assessment of relative humidity from dry and wet thermometer readings using the psychrometric chart provided on the instrument.

Hygrometers are devices for the direct determination of the relative humidity of the air. The sensitive element of hygrometers is a human hair degreased in ether or alcohol (or a special synthetic film), which is connected in a certain way with a light pointer. With a decrease in relative humidity, the sensitive element is shortened, and with an increase it is lengthened, moving the end of the pointer along the scale with divisions from 0 to 100% relative humidity. The hygrometer is the only instrument for determining humidity at negative temperatures, but its accuracy does not exceed 5%.

Air speedmeasured with catathermometers and anemometers (vane, cup and thermoelectric).

Catathermometer designed to measure low air velocities (from 0,04 up to 2 m/s) in service and amenity premises. The principle of operation of the device is based on the determination of the cooling power of the air. The catathermometer is an alcohol thermometer with a scale of 35 to 38° C. The amount of heat lost by the catathermometer when it is cooled from 38 to 35° C, constant, and the duration of cooling depends on the action of all meteorological factors.

To prepare the catathermometer for measurements, its tank with alcohol is gently heated in water.(60 70° C) until the alcohol fills 1/5 1/3 volume of the upper expansion of the capillary, then the device is wiped dry, suspended in the place under study (as far as possible from heat-radiating devices) and the time of cooling of the catathermometer from 38 to 35° C. Thus, in essence, the instrument measures the cooling capacity of air at human body temperature. Air speed ( V , m/s) is determined by empirical formulas:

V = 6.25 (f /∆t 0.5) 2 at f /∆t< 0,6 ; (5)

V = 4.53(f /∆ t 0.13) 2 for f /∆ t ≥ 0.6 , (6)

Where f = F / T to air cooling capacity, cal/cm 2 s;

F \u003d 472 cal / cm 2 catathermometer parameter that determines the amount of heat lost from 1 cm 2 catathermometer tank (indicated by the manufacturer on the device);

T to Catathermometer cooling time measured with a stopwatch (from 38 to 35 ° C), s;

∆t difference between average temperature catathermometer (36.5 °C) and ambient temperature.

winged and cup anemometersconsist of a sensing part rotating under the action of an air flow, and a counting mechanism. A vane anemometer is used to determine free air flow velocities from 0.3 to 5 m/s, and cup from 1 to 20 m/s. To determine the speed of the air flow, using anemometers, the speed of rotation of the receiving part is determined for a certain time according to the readings of the counting mechanism (number of divisions per second) and, according to a special schedule, it is converted into linear air speed, m/s.

barometers instruments for measuring atmospheric pressure. The most common aneroid barometer, the principle of operation of which is based on the use of elastic deformations of the membranes of aneroid boxes under the influence of changes in atmospheric pressure.

Work order

1. To study the purpose and principle of operation of the main instruments for measuring microclimate parameters.
2. Determine the air temperature at the workplace (using a “dry” thermometer household psychrometer) and barometric (atmospheric) pressure (750 mm Hg. St.. = 1000 hPa).
3. Based on the readings of the psychrometer, calculate the relative humidity at the workplace using formula (3) and the absolute humidity from formula (1).
4. According to the task option (brigade number), using the data from the table on the stand, perform the following calculations:
5. according to formula (2) determine the air temperature in the room in the presence of sources of significant thermal radiation (data from the table of options);
6. determine the speed of air movement in the room, using the data from the table of options, according to formulas (5) and (6) for the catathermometer or according to the graph on the stand for the anemometer;
7. according to the readings of the “dry” and “wet” thermometers of the psychrometer, calculate using the formulas(3) or (4) the relative humidity of the air in the room, and according to the formula(1) absolute humidity;
8. determine the equivalent-effective temperature in the room from the nomogram, using the results of paragraphs. a ), b ), c ), and draw a conclusion about the compliance with her comfort zone.
9. Using a nomogram to determine the equivalent effective temperature, plot its dependence on air velocity: EET \u003d F (V) at φ \u003d const and t c \u003d const. Data for “dry” and “wet” thermometers are taken from the options table on the stand. Set the air velocity according to the corresponding curves of the nomogram.
10. Using a nomogram to determine the equivalent effective temperature, plot the equivalent effective temperature versus relative air humidity EET \u003d F (φ) at V \u003d const and t c \u003d const . To build a graph, you should set several temperature values ​​​​on the scale of a “wet” thermometer ( t in ), data for the temperature value on the scale of the “dry” thermometer ( tc ) is taken from the table of options on the working stand, and the air velocity ( V ) from calculations according to clause 4, b . The calculation of relative humidity values ​​for each pair of values ​​of “dry” and “wet” thermometers is carried out according to the formula (3).

1. The results of measurements and calculations are summarized in a table of final results (Table 4).

Table 4

results measurements and calculations

For workplace						By assignment option
var ianta	t С, °С	t V , °С	φ , %	P ATM , hPa	THIS	t HEAT, °C	V, m/s	φ , %	P ATM , hPa	E E T

Control questions

1. How is heat exchanged between the human body and the environment?
2. The main parameters of the microclimate.
3. Influence of microclimate parameters on the human body.
4. What is the equivalent effective temperature?
5. Comfortable meteorological conditions.
6. Principles of regulation of microclimate parameters.
7. Optimal and permissible microclimatic conditions.
8. Purpose and principle of operation of meteorological instruments.

Bibliographic list

1. Life safety: Textbook for universities / Ed. S.V. Belova. Moscow: Higher school, 2004.

2. Life safety: Textbook for universities / Ed. E.A. Arustamov. Moscow: ID Dashkov i K o, 2003.

3. Razdorozhny A.A. Safety of industrial activity: Proc. allowance for universities. M.: Infra-M, 2003.

4. SanPiN 2.2.4.548-96 " Hygiene requirements to the microclimate of industrial premises.

5. GOST 12.1.005-88.SSBT. General sanitary and hygienic requirements for the air of the working area.

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The microclimate of domestic and industrial premises is determined by the combinations of temperature, humidity and air velocity acting on the human body.

The main requirement that ensures normal living conditions for a person during a long stay in the room is the optimal combination of microclimate parameters. First of all, they must eliminate the tension of the body's thermoregulation mechanisms or maintain health and performance. Deviations of individual microclimate parameters from biomedical reasonable values ​​can lead to various diseases, especially in people with weakened immune systems.

It is known that lowering the temperature causes increased heat transfer to the environment, which causes cooling of the body, lowers its protective functions and contributes to the occurrence of colds. On the contrary, an increase in temperature leads to an increased release of salts from the body, and a violation of the salt balance of the body also leads to a decrease in immunity, a significant loss of attention, and, consequently, to a significant increase in the likelihood of an accident.

An increase in air humidity disrupts the balance of moisture evaporation from the human body, which leads to a violation of thermoregulation with the above-mentioned consequences. On the other hand, a decrease in relative humidity (up to 20% and below) disrupts the normal functioning of the mucous membranes of the upper respiratory tract. The speed of air movement is also a factor influencing the mechanism of thermoregulation of the body.

It has been established that the action of the air flow depends on the room temperature and affects the human condition at a speed of 0.15 m/s. Such a flow at a temperature of less than 36 ° C has a refreshing effect and promotes thermoregulation, and at a temperature of more than 40 ° C it has the opposite effect.

Medical and biological optimal norms of microclimate parameters are set taking into account the period of the year, while it is considered that in the warm period of the year (spring, summer) the average daily temperature of the outside air is +10 ° C, in the cold period (autumn, winter) the average daily temperature of the outside air is -10 °C. In both cases, the optimal relative humidity is taken within 40 - 60%.

If we talk about the microclimate of industrial premises, then it is determined by the category of work that is performed in them. GOST 12.1 005-76 provides for three categories of work:

Light physical.

Physical moderate.

Severe physical.

In this case, the job of a software engineer is light physical work. Energy costs of the body during the performance of work - 120 - 170 kcal / h. The work is done while sitting, standing, or associated with walking and is accompanied by minor physical stress (mostly people of mental labor).

In table. 5.1 shows the optimal allowable values ​​of the microclimate parameters of industrial premises in the cold and warm periods of the year for light physical work.

As can be seen from the table below, all microclimate parameters are related to air, so the level of its pollution is of great importance. It is known that during the production process, harmful substances can be released into the air, which enter the human body through the respiratory tract.

To ensure the necessary parameters of the microclimate and purify the air in industrial premises, various ventilation systems. Types and designs of ventilation systems is a separate topic, which is not considered in this section. The main requirement for any ventilation system is to ensure the necessary air exchange rate, which ensures the removal of all harmful components from the production room, that is, excess heat, moisture, vapors of various substances.

Table 5.1

Optimal allowable values ​​of microclimate parameters

The room in which the workplace of a software engineer is located has the following characteristics:

room length: 5 m;

room width: 6 m;

room height: 2.7 m;

number of windows: 1;

number of jobs: 1;

lighting: artificial;

number of computers: 1.

Under the frequency rate of air exchange is understood:

where L B - the amount of air entering (or removed) into the room, m 3 / h;

V P - the volume of the room, m 3.

In the presence of excess heat, the amount of air that needs to be removed from the room,

(5.4)

Where Q izb – excess heat, kcal/h;

C B is the heat capacity of air (0.24 kcal/kg K);

t- the temperature difference between the incoming and incoming air;

\u003d 1.206 kg / m 3 - specific gravity of the supply air.

Excess heat:

Where Q about, Q osv, Q l - heat generated by production equipment, artificial lighting system and working personnel, respectively;

Q p – heat introduced by solar radiation;

Q otd - Heat dissipation in a natural way.

Heat generated by production equipment:

Where 860 – thermal equivalent 1 kW/h;

R o6 – power consumed by the equipment, kW;

-coefficient of heat transfer to the room;

Initial data R about = 1; = 0.5; calculate

:

Heat generated by lighting installations:

Where R osv - power of lighting installations, kW;

–Efficiency of conversion of electrical energy into thermal energy;

– Efficiency of simultaneous operation of equipment in the room;

cos – electrical coefficient;

– phase shift angle between current and voltage;

Initial data R osv = 0,2;= 0,2;= 0.8; cos = 0.8, calculate

:

Heat generated by people:

Where TO l - the number of workers;

(q-q Spanish ) - sensible heat, determined by special graphs, kcal / h,

Where q– heat dissipation of one person for the corresponding category of work;

q Spanish is the heat expended for evaporation by the body;

Initial data TO l = 1;(q-q Spanish ) = 120 , let's calculate

kcal/h

Heat generated by solar radiation:

(5.6)

Where T- the number of windows in the room;

F– the area of ​​one window, m 2;

q ost - the amount of heat introduced in one hour through a glazed surface with an area of ​​\u200b\u200b1m 2 (table value) kcal / h * m 2.

In rooms with large excess heat Q otd = Q R. For the warm season Q otd = 0.

From the calculated parameters Q about , Q osv , Q l , Q R , Q otd we can calculate the excess heat, the amount of air to be removed from the room and the air exchange rate.

Initial data for calculating excess heat Q about = 430;Q osv = 22,02;Q l = 120;Q R -Q otd= 0, calculate the excess heat using formula 5.5:

Initial data for calculation Q hut = 572,02;C V = 0,24;= 1,2;

\u003d 6, we calculate the amount of air that needs to be removed from the room, according to formula 5.4:

Knowing these parameters, it is easy to calculate the air exchange rate according to formula 5.3, which will be equal to:

Air purification from dust and the creation of optimal microclimate parameters at the workplace of a software engineer is provided by a ventilation (air conditioning) system.