METHODICAL INSTRUCTIONS FOR PRACTICAL STUDIES in GENERAL HYGIENE FOR STUDENTS of 3 COURSE OF MEDICAL FACULTY # 1 (7 hours)

THE HYGIENICAL ESTIMATION OF THE COMPLEX INFLUENCING OF PARAMETERS OF MICROCLIMATE ON THE HEAT EXCHANGE OF MAN. HYGIENIC ESTIMATION OF NATURAL AND ARTIFFICIAL ILLUMINATION.

 

Health - is defined as a state of complete physical, mental and social well-being and not merely absence of disease or infirmity.

Hygiene - is a basic preventive science in medicine. It generalizes all dates of theoretical and clinical disciplines in the field of prophylaxis, integrates knowledges about complex influence of an environment for health of the man, work out principles and systems of preventive measures.

The word Hygiene is derived from the Greek word (Hygeia) Hygieia the goddess of health.

: : 180px-Klimt_hygeia

PREVENTIVE MEDICINE

Prevention is better than cure is an old saying. Preventive medicine deals with the measures to protect the individuals from the diseases, and to keep them in a state of positive health. For this we have to ensure all the above-mentioned prerequisites required for the maintenance of positive health. The environments must be hygienic, with supply of fresh air, safe potable water and balanced diet. This aspect of preventive medicine started gaining more importance from 18th century onwards with the discovery of various vaccines and sera for the protection against various diseases like small pox, cholera, plague, whooping cough, tetanus, tuberculosis, poliomyelitis etc

 

THE METHOD OF DETERMINATION AND HYGIENIC ESTIMATION OF AIR TEMPERATURE AND ATMOSPHERIC PRESSURE

TEMPERATURE SCALES

One of the earliest temperature scales was devised by the German physicist Gabriel Daniel Fahrenheit. According to this scale, at standard atmospheric pressure, the freezing point (and melting point of ice) is 32 F, and the boiling point is 212 F. The centigrade, or Celsius scale, invented by the Swedish astronomer Anders Celsius, and used throughout most of the world, assigns a value of 0 C to the freezing point and 100 C to the boiling point.

http://www.ux1.eiu.edu/~cfadd/1360/19Temp/Absolute.html

In scientific work, the absolute or Kelvin scale, invented by the British mathematician and physicist William Thomson, 1st Baron Kelvin, is used. In this scale, absolute zero is at -273.16 C, which is zero K, and the degree intervals are identical to those measured on the Celsius scale. The corresponding absolute Fahrenheit or Rankine scale, devised by the British engineer and physicist William J. M. Rankine, places absolute zero at -459.69 F, which is 0 R, and the freezing point at 491.69 R. A more consistent scientific temperature scale, based on the Kelvin scale, was adopted in 1933.

An absolute temperature scale invented in the 1800's by William Thompson, Lord Kelvin. It places the zero point of the scale at absolute zero, the temperature which scientists believe is the lowest possible. All molecular motion would stop there. A Kelvin degree is the same size as a Celsius degree, so the two scales simply have a constant offset.

: : Fahrenheit, Celsius and Kelvin temperature scales

 

Temperature.

An instrument called thermometer ascertains this.

Name of

thermometer

Boiling

point

Freezing

point

Fahrenheit

32

212

Centigrade (Calcius)

0

100

Reaumur

0

80

: : temperature

Generally mercury or alcohol is used in the thermometers. Mercury is used in thermometers meant for recording high temperatures on account of its uniformity in expansion at different temperatures, easy visibility, high boiling point and low vapor pressure. Alcohol is used in thermometers for recording low temperatures, because it does not freeze even at low temperatures. Several kinds of thermometers are used

These are:

(1)Standard or Dry Bulb Thermometer. It is an ordinary thermometer.

(2)Maximum Thermometer. It is used for registering the highest temperature attained in the day or any other period. The thermometer is laid in a horizontal position. In the stem of the thermometer, part of the mercury column is separated by air. When the temperature rises the mercury expands and pushes this broken column forward. But this column does not recede when the temperature falls and the main mercury column contracts. The reading taken indicates the maximum temperature attained during the day.

(3) The Minimum Thermometer. It is used for recording the lowest temperature during the night or during the early hours of morning. A small glass index is enclosed in the spirit, which fills the bulb and a part of the stem. When setting the instrument, the index is first brought to the top of the column of the spirit and the instrument is placed in a horizontal position. When the temperature rises, the spirit expands and flows past the index, but when the temperature falls, the spirit contracts and carries the index along with it. The lowest temperature is thus registered. The instrument can be readjusted by tilting.

(4) Six's Maximum and Minimum Thermometer. It is a combination of maximum and minimum thermometers and gives a double reading. It is however, not a very accurate instrument and is therefore no more being used now in Indian Meteorological observatories.

: : Image1

Methods of temperature measure

On value of temperature regime on the room measure do in difference place on a vertical.

First measure of temperature is done on 10 cm from the floor and characterizes air on foot level.

Second measure do on 1,5 meter from the floor in respiration zone of man.

Third place is on 50 cm from ceiling and characterizes convection in the room. In hospital the second place is situated on level of bad. Measuring of temperature in horizontal line is done in three points: from external angle to internal angle on 20 cm. Change of temperature in time is measured by thermograph. Its done in three places on 1,5 cm from the floor.

 

Thermometer

It is instrument used to measure temperature. The invention of the thermometer is attributed to Galileo, although the sealed thermometer did not come into existence until about 1650. The modern alcohol and mercury thermometers were invented by the German physicist Gabriel Fahrenheit, who also proposed the first widely adopted temperature scale, named after him.

: : thermometer

Types of thermometers

Wide variety of devices are employed as thermometers. The primary requirement is that one easily measured property, such as the length of the mercury column, should change markedly and predictably with changes in temperature.

Electrical resistance of conductors and semiconductors increases with an increase in temperature. For thermistor of given composition, the measurement of specific temperature will induce specific resistance. This resistance can be measured by galvanometer and becomes measure of the temperature. With proper circuitry, the current reading can be converted to a direct digital display of the temperature.

: : Digital_Thermometer

Very accurate temperature measurements can be made with thermocouples in which small voltage difference (measured in millivolts) arises when two wires of dissimilar metals are joined to form a loop, and the two junctions have different temperatures.

Optical pyrometer is used to measure temperatures of solid objects at temperatures above 700 C (about 1300 F) where most other thermometers would melt. At such high temperatures, solid objects make so-called glow color phenomenon. The color at which hot objects glow changes from dull red through yellow to nearly white at about 1300 C (about 2400 F). The pyrometer contains a light bulb type of filament controlled by a rheostat (dimmer switch) that is calibrated so that the colors at which the filament glows corresponding to specific temperatures.

Another temperature-measuring device, used mainly in thermostats, relies on the differential thermal expansion between two strips or disks made of different metals and either joined at the ends or bonded together.

Special types of thermometers

Thermometers may also be designed to register the maximum or minimum temperature attained.

Maximum thermometers.A mercury-in-glass clinical thermometer, for example, is maximum-reading instrument in which trap in the capillary tube between the bulb and the bottom of the capillary permits the mercury to expand with increasing temperature, but prevents it from flowing back unless it is forced back by vigorous shaking.

Minimum thermometers. Inside capillary tube is alcohol with glass pin. When temperature increase ethanol moves pin. When temperature decrease ethanol paces pin for a minimal temperature.

Thermograph.

Thermograph consists of vertical pen, bimetallic laminas and clack mechanism. Perceiving part of instrument is bimetallic laminas, which change it curvature by change of temperature. By means system of levers which passes changing curvature of bimetallic laminas by righting pen and we have graphical illustration of temperatures on paper of clack mechanism.

: : Image4

Table of Equivalent Temperatures by Celsius and Fahrenheit scales

C = (F - 32) 100/180;

F = (C 180/100) + 32.

 

Measuring Maximum and Minimum temperature

If possible it is best to record the daily maximum and minimum temperature as well as that which you record at a specific moment in time when you make your observations. You can simply use your normal thermometer. With this you need to record temperatures at about 14:00 where the daily maximum usually occurs, or very early morning when the temperature is similar to the overnight minimum. These are good times to take your am/pm measurements.

Studying the temperature condition of the indoor air

 

The temperature is measured in 6 or more points to fully characterize the temperature conditions of premises.

Thermometers (mercurial, alcohol, electric or psychrometer dry thermometers) are placed onto support racks at three points 0.2 meter high above the floor, at three points 1.5 meters high (points t2, t4, t6 and t1, t3, t5 respectively) and at 20 cm from the wall along the diagonal section of the laboratory according to the diagram:

. t1

t2

. t3 . t1 . t3 . t5

t4

t5

. t6 . t2 . t4 . t6

 


) plan of premises; b) vertical section of premises.

 

The thermometer data are fixed after 10 minutes of the exposition at the point of measurement.

The air temperature parameters in premises are calculated using following formulas:

) the average temperature in the premises:

 

) taver.= ,

 

b) the vertical variation of the air temperature:

Dtvert.. = - ,

 

c) the horizontal variation of the air temperature:

Dthor..= -

 

Diagrams and calculations are written down into the protocol, the hygienic assessment is made. It is necessary to consider the following data: the optimal air temperature must be from +18 to +21 in residential and class-room premises, wards for somatic patients, the vertical temperature variation must be no more than 1.5-2.0, horizontal - no more than 2.0-3.0. The daily temperature variations are determined using the thermogram, prepared in laboratory using the thermograph. The daily temperature variation must be no more than 6.

The allowable and optimal standards of the temperature, presented in the table 1 are the hygienic assessment criteria for residential and public premises.

 

Table 1

 

The temperature standards for residential, public and administrative premises

 

 

Season

 

Temperature

Optimal

Allowable

Warm

20-22

23-25

No more than 3 higher than the estimated outdoor air temperature*

Cold and transitional

20-22

18 22**

 

Comment:

* the allowable temperature is no more than 28 for public and administrative premises, which are permanently inhabited, for regions with the estimated outdoor air temperature of 25 and above no more than 33.

** the allowable temperature is 14 for public and administrative premises where the inhabitants are wearing their street clothes.

 

The standards were established for people that are continuously staying in the premises for 2 hours or more.

 

The temperature standards for the workplace air of industrial areas are set in the State Standard #12.1.005-88 General sanitary and hygienic requirements to the workplace air, depending on the season (cold, warm) and work category (easy, moderate and hard).

The optimal temperature standards for the cold season are set from 21 to 24 during the physically easy work and from 16 to 19 during the physically hard work. These temperature ranges correspond to 22-25 and 18-22 during the warm season. The allowable maximum temperature is no more than 30 for the warm season, the allowable minimum temperature for the cold season is 13.

 

Appendix 2

 

The radiant temperature and the wall temperature determination

 

The spherical thermometers are used for the radiant temperature determination in premises, wall thermometers for the wall temperature determination (see fig. 6.1 , b)

The spherical thermometer consists of the thermometer located inside the hollow sphere 10-15 cm in diameter and covered with porous polyurethane foam layer. This material has similar coefficients of the infrared radiation adsorption as the human skin.

The radiant temperature is also determined at 0.2 and 1.5 meters above the floor.

The device has the considerable inertia (up to 15 min.), that is why the thermometer data must be taken no earlier than after that time.

The spherical thermometer data at the height of 0.2 and 1.5 m must not vary by more that 3 in comfortable microclimate conditions.

: : topic6_0

Fig. 6.1. Thermometers for the radiant temperature determination

a the section of the spherical black thermometer

(1 15 cm diameter sphere covered with dull black paint; 2 thermometer with the reservoir at the center of the sphere)

b Wall thermometer with the flat turbinal reservoir

(1 thermometer; 2 base cover (foam-rubber); 3 sticky tape)

The values of the radiant temperature below are recommended for different premises (see table 2).

Table 2

 

Standard values of radiant temperature for different premises

 

Type of premises

Radiant temperature,

 

Residential premises

20

Classrooms, laboratories

18

Lecture-rooms. halls

16-17

Gymnasiums

12

Bathrooms, swimming pools

21-22

Hospital wards

20-22

Doctors consulting rooms

22-24

Operating room

25-30

 

Special thermometers with the flat turbinal reservoir are used for the wall temperature determination. These thermometers are attached to the wall with special putty (wax with colophony addition) or alabaster. The wall temperature is also determined at 0.2 and 1.5 meters above the floor. In some cases it is necessary to determine the temperature of coldest parts of the wall.

The high levels of infrared irradiation in especially hot manufacture areas are measured using actinometers (solar radiation instrument) and are expressed in mcal/(m2×min).

 

Water vapor

The person during all life is exposed to water vapor. Its quantity in air permanently changes: it decreases or increases. When in air a lot of water vapor is stored, the conditions for evaporation of moisture are worse. In air such quantity of water vapor can be stored, that it resilience equals resilience of liquid that evaporates, - and then the evaporation ceases.

The evaporation depends on temperature of air, the above last, the implements evaporation fan-in harder. There fore evaporation as though goes after temperature of air; temperature of air - is increased the evaporation is increased also; temperature of air is lowered, the evaporation is lowered also.

Air humidity

Humidity is moisture content of the atmosphere. The atmosphere always contains some moisture in water vapor; the maximum amount depends on the temperature. The amount of vapor that will saturate the air increases with temperature rise. At 4.4 C (40 F), 454 kg (1000 lb) of moist air contain maximum 2 kg of water vapor; at 37.8 C (100 F), the same amount of moist air contains maximum 18 kg of water vapor. When the atmosphere is saturated with water, the level of discomfort is high because the evaporation of perspiration, with its attendant cooling effect, is impossible.

Humidity is specified in several different ways. The weight of water vapor contained in a volume of air is known as the absolute humidity and is expressed in grams of water vapor per cubic meter.Relative humidity, given in weather forecasts, is the ratio between the actual content of the air vapor and the content of the air vapor at the same temperature saturated with water vapor.

The maximum damp is measured by that quantity of a water pair in grammas, which one saturates completely 1m3 of air at given temperature

The relative humidity is an attitude of absolute humidity to maximum at given temperature, expresses in percentage, that is:

R=A / F 100,

Where R - relative humidity;

A- absolute humidity;

F - maxime humidity.

The relative humidity interests us because its characterize saturation of air by a pair, its dryness. For example, if we speak, that relative humidity 60 %, from this number it is visible, that 40 % of a moisture does not suffice to saturation of air, that is, it has a capability to receive a moisture. At relative humidity 80 % we could say, that in this case elasticity of a pair in atmosphere is higher, at her the liquid evaporates worse. At 90 % - it is even worse.

Knowing absolute humidity it is possible to definite dew point, that is that temperature, at which one the absolute humidity becomes maximum and the air humidity will begin to be condensate and to precipitate by the way of drops of water. Let's consider such example. What the temperature this damp will begin to saturate air? It also means to find dew point.

The air humidity can be described as deficit of saturation. The deficit of saturation is a difference between maximum and absolute humidity at same temperature. Together with it there is also concept a physiological deficit of saturation. It - difference between maximum damp at the temperature of bodies of the person 36,5 degree and absolute humidity of air.

Physiological relative humidity

Hygiene uses also concept of physiological relative humidity. It is attitude of absolute humidity at given temperature of air to maximum at 36,5 degree, expressed in percentage. Physiological relative humidity characterizes capability of air to accept damp that evaporates at body temperature. It enables more precisely to evaluate effect of moist air.

Air humidity can be described as deficit of saturation. The deficit of saturation is difference between maximum and absolute humidity at same temperature.

There is also a concept of physiological deficit of saturation. It is difference between maximum damp at body temperature person 36,5 degree and absolute humidity of air. The physiological deficit of saturation lets us define how many grams of water the person can spend by evaporation in given conditions.

Air humidity is very relevant hygienic factor because it influences thermo exchange of the person. At low temperatures in moist air the feeling of cold is stronger than in dry air at the same temperature.

It is by outcome that the moist air has large heat conductivity and thermal capacity. From the same reason in wet clothes it is much more cold: pores of tissues charged with moisture, and its well carries out heat.

Human body permanently loses moisture either by water vapor or by liquid water. It is established that in quiet condition at room temperature the person loses by skin approximately 20% of moisture, mild - 15 %, remaining part - urine and feces. Therefore, in these conditions approximately 35% of water is lost by evaporation and 65% - in liquid with feces and urine. By activity and heat of air in the contrary: 60% of water is lost by evaporation from skin and mild and much less by urine and feces.

Normal relative air humidity in dwelling apartments is 30-60%. A great range of normal air humidity is explained fluctuations by the fact , that its influence on the organism depends on a number of conditions. In peace when the air temperature is 16-200 with a light air motion the optimum humidity will be 40 - 60%. During physical work when the air temperature is above 200 or below 150 air humidity must not be more than 30-40%, and when the temperature above 25 0 desirable to bring relative humidity down to 20%.

 

Air humidity determination methods

: : psychrom: : assman psychrom

Humidity is determined by psychrometes and hygrometers. Hygrographs determine humidity fluctuations for a day or a week. Absolute air humidity is determined by psychrometes (from greek psychros - cold).Psychrometes are of August and Assman types.

August psychrometer consists of two identical mercury thermometers fixed on a support. By temperature difference on dry and humid thermometers we can define absolute air humidity with a help of table or formula.

Assman psychrometer consists of dry and humid thermometer situating in metal casing that protects from radiation temperature. There is a ventilator in the upper part of the device. Ventilator is wound up and during 5 minutes in summer (15 minutes in winter) registers a temperature difference.

Relative humidity is measured by hygrometer. It consists of metal frame in the middle of which a fair defatted womans hair is lightened. When humidity is low the hair becomes shorter, when it is high it becomes longer.

Instruments to Measure Humidity

A whirling psychrometer is a type of hygrometer which can be whirled around like a football rattle to take readings. You can directly read off the percentage relative humidity. It is a good idea to wrap it in a damp cloth for a while and then set the dial to read 100 %. Like paper, human hair stretches when moist and shrinks when dry. Humidity recorders use this principle, and you can make a simple hygrometer using this method.

http://www.piercecollege.com/offices/weather/psychrometer.html

Psychrometer Assmana

: : F:\lototska\Assman psychrom 2.files\psych.files\psycro.jpg

The Psychrometer measures the wet and dry bulb temperature and under natural evaporation conditions the state of a given mass of air can be described by its temperature and vapor pressure. If water is allowed to evaporate in an isolated mass of unsaturated air , it latent heat content increases and its sensible heat content decreases. The process will stop when the air becomes saturated at the wet bulb temperature ( Tw). The change in latent heat must equal the change in sensible heat. http://weather.nmsu.edu/Teaching_Material/soil698/psych.html

Psychrometer

: : F:\lototska\psychrometer.files\e_dry2wet.files\e_dry2wet.jpg

A pair of thermometer placed parallel inside the screen with a bare bulb on the right indicating the air temperature and is called dry bulb thermometer. Another thermometer on the left whose blackened globe is covered with a moistened muslin wick is called wet bulb thermometer. Since they are usually using in a pair, therefore, we normally call them psychrometer. 

 

: : Image3

The absolute humidity is calculated using the Regnault formula:

= f a · (t - t1) · B,

 

where, the air absolute humidity at the current temperature in Hg mm;

f maximum pressure of water vapour at the wet thermometers temperature (see the table of saturated water vapours, table 3);

psychrometric coefficient is 0.0011 for enclosed spaces;

t temperature of the dry thermometer;

t1 temperature of the wet thermometer;

barometric pressure during the humidity determination, Hg mm.

The relative humidity is calculated using the following formula:

P = ,

where, the value of relative humidity to be found, %;

absolute humidity, Hg mm;

F maximum pressure of water vapour at the dry thermometer temperature, Hg mm (see the table of saturated water vapours, table 3).

Table 3

Maximum pressure of the air water vapour of premises

 

Air temperature,

Water vapour pressure, Hg mm

Air temperature,

Water vapour pressure, Hg mm

-20

0.94

17

14.590

-15

1.44

18

15.477

-10

2.15

19

16.477

-5

3.16

20

17.735

-3

3.67

21

18.630

-1

4.256

22

19.827

0

4.579

23

21.068

1

4.926

24

22.377

2

5.294

25

23.756

4

6.101

26

25.209

6

7.103

27

26.739

8

8.045

30

31.843

10

9.209

32

35.663

11

9.844

35

42.175

12

10.518

37

47.067

13

11.231

40

53.324

14

11.987

45

71.83

15

12.788

55

118.04

16

13.634

100

760.0

 

Psychrometric tables for the August psychrometer are used for the relative humidity (RH) determination (if the air velocity is 0.2 m/sec.). The value of RH is found at the point of the dry and wet thermometers data intersection, table 4.

The psychrometer operation is based on the fact that the rate of the water evaporation from the surface of dampened psychrometers reservoir is proportional to the air dryness. The drier the air the lower is the wet thermometers result in comparison to the dry thermometer due to the latent evaporation.

 


Determination of the relative humidity using the August psychrometer

 

Dry thermometer data

Wet thermometer data, º

12

5.3

5.7

6.0

6.4

6.8

7.2

7.6

8.0

8.4

8.7

9.1

9.5

9.9

10.3

10.7

11.0

11.3

11.7

12.0

13

5.9

6.4

6.8

7.2

7.6

8.0

8.4

8.8

9.2

9.6

10.0

10.4

10.8

11.1

11.5

11.8

12.2

12.6

13.0

14

6.6

7.1

7.5

8.0

8.4

8.6

9.2

9.7

10.1

10.5

10.9

11.3

11.7

12.1

12.5

12.8

13.2

13.6

14.0

15

7.3

7.8

8.2

8.7

9.2

9.6

10.0

10.5

10.9

11.4

11.8

12.2

12.6

13.0

13.4

13.8

14.2

14.6

15.0

16

8.0

8.5

9.0

9.4

9.9

10.3

10.8

11.3

11.8

12.2

12.6

13.1

13.5

14.0

14.4

14.8

15.6

15.6

16.0

17

8.0

9.1

9.7

10.2

10.7

11.2

11.6

12.1

12.6

13.0

13.5

13.9

14.4

14.9

15.3

15.8

16.2

16.6

17.0

18

9.3

9.9

10.4

10.9

11.4

11.9

12.4

12.9

13.4

13.9

14.4

14.8

15.3

15.7

16.2

16.6

17.1

17.5

18.0

19

10.0

10.6

11.1

11.7

12.2

12.7

13.2

13.8

14.8

14.8

15.3

15.7

16.2

16.7

17.2

17.6

18.1

18.5

19.0

20

10.6

11.2

11.8

12.4

12.9

13.4

14.0

14.5

15.1

15.6

16.1

16.6

17.1

17.6

18.1

18.5

19.0

19.5

20.0

21

11.2

11.9

12.6

13.1

13.6

14.2

14.8

15.3

15.9

16.6

17.1

17.5

18.0

18.6

19.1

19.5

20.0

20.5

21.0

22

11.8

12.5

13.2

13.8

14.4

15.0

15.6

16.1

16.7

17.3

17.9

18.4

18.9

19.5

20.0

20.5

21.0

21.5

22.0

23

12.5

13.1

13.8

14.4

15.1

15.7

16.4

17.0

17.6

18.2

18.8

19.3

19.8

20.4

20.9

21.5

22.0

22.5

23.0

24

13.1

13.8

14.5

15.2

15.9

16.5

17.1

17.8

18.4

19.0

19.6

20.1

20.7

21.3

21.9

22.4

23.0

23.0

24.0

25

13.7

14.5

15.2

15.9

16.6

17.2

17.9

18.5

19.2

19.8

20.5

21.2

21.7

22.2

22.8

23.3

23.9

24.4

25.0

Relative humidity,%

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

 

 


Determination of the air humidity using the Assmann aspiration psychrometer

The significant disadvantage of August psychrometer is its dependence on the air velocity. The air velocity influences the evaporation intensity and the devices wet thermometer cooling.

This disadvantage has been eliminated in Assmann psychrometer due to the usage of the ventilator (see fig. 6.2-b). The ventilator produces the constant air movement at the 4 m/sec speed near thermometers reservoirs. As a result data does not depend on the air velocity either inside or outside of the premises. Furthermore, thermometers; reservoirs of this psychrometer are protected with reflecting cylinders around psychrometers reservoirs from the radiant heat.

The cambric of Assmann aspiration psychrometer wet thermometer is dampened using the pipette, the spring of the aspiration devise is set or the psychrometer with electrical ventilator is plugged in. After these procedures the psychrometer is hung up onto the support at the determination point. The data of wet and dry thermometers are taken 8-10 minutes later.

The absolute air humidity is calculated using the Sprung formula:

,

where: absolute air humidity in Hg mm;

t maximum pressure of water vapour at the wet thermometer temperature (see the table of saturated water vapours, table 3);

0.5 constant psychometric coefficient;

t temperature of the dry thermometer;

t1 temperature of the wet thermometer;

barometric pressure at the determination moment in Hg mm.

 

Relative humidity is determined using the following formula:

,

where: the value of relative humidity to be found, %;

absolute humidity, Hg mm;

F maximum humidity at the dry thermometer temperature, Hg mm (see table 3).

 

Relative humidity is determined using the psychrometric tables for aspiration psychrometers. The value of the relative humidity is found at the intersection point of the dry and wet thermometer data (see table 5).

Hair or membrane hygrometers are used for the determination of the relative humidity of the air. These devices measure the relative humidity directly. The hygrometer operation is based on the facts, that the degreased hair lengthens, and the membrane/diaphragm weakens when its damp, and vice-versa when they are dry (see fig. 6.2-c).

 


Table 5

Determination of the relative humidity based on the Assmann psychrometer data, %

 

Dry thermometer indices

Wet thermometer indices, º

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

15.0

16.0

17.0

18.0

19.0

20.0

21.0

22.0

23.0

24.0

25.0

26.0

27.0

8.0

29

40

51

63

75

87

100

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

9.0

21

31

42

53

64

76

88

100

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

10.0

14

24

34

44

54

65

76

88

100

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

11.0

 

17

26

36

46

56

66

77

88

100

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

12.0

 

 

20

29

38

48

57

58

78

88

100

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

13.0

 

 

14

23

31

40

49

59

69

79

89

100

 

 

 

 

 

 

 

 

 

 

 

 

 

 

14.0

 

 

 

17

25

33

42

51

60

70

79

90

100

 

 

 

 

 

 

 

 

 

 

 

 

 

15.0

 

 

 

 

20

27

36

44

52

61

71

80

90

100

 

 

 

 

 

 

 

 

 

 

 

 

16.0

 

 

 

 

15

22

30

37

46

54

63

71

81

90

100

 

 

 

 

 

 

 

 

 

 

 

17.0

 

 

 

 

 

17

24

32

39

47

55

64

72

81

90

100

 

 

 

 

 

 

 

 

 

 

18.0

 

 

 

 

 

13

20

27

34

41

49

56

65

73

82

91

100

 

 

 

 

 

 

 

 

 

19.0

 

 

 

 

 

 

15

22

29

36

43

50

58

66

74

82

91

100

 

 

 

 

 

 

 

 

20.0

 

 

 

 

 

 

 

18

24

30

37

44

52

59

66

74

83

91

100

 

 

 

 

 

 

 

21.0

 

 

 

 

 

 

 

14

20

26

32

39

46

53

60

67

75

83

91

100

 

 

 

 

 

 

22.0

 

 

 

 

 

 

 

 

16

22

28

34

40

47

54

61

68

76

84

92

100

 

 

 

 

 

23.0

 

 

 

 

 

 

 

 

13

18

24

30

36

42

48

55

62

69

76

84

92

100

 

 

 

 

24.0

 

 

 

 

 

 

 

 

 

15

20

26

31

37

43

49

56

63

70

77

84

92

100

 

 

 

25.0

 

 

 

 

 

 

 

 

 

 

17

22

27

33

38

44

50

57

63

70

77

84

92

100

 

 

26.0

 

 

 

 

 

 

 

 

 

 

14

19

24

29

34

40

46

52

58

64

71

77

85

92

100

 

27.0

 

 

 

 

 

 

 

 

 

 

 

16

21

25

30

36

41

47

52

58

65

71

78

85

92

100

 

 


Table 4

The relative humidity standards for residential, public and administrative premises (abstract from Building Norms and Rules 2.04.05-86)

 

Season

Relative humidity, %

Optimal

Allowable

Warm

30-60

65*

Cold and transitional

30-45

65

 

Note:* Allowable humidity is 75% for regions with the estimated outdoor air relative humidity more than 75%.

Standards are set for people who continuously stay in premises for more than 2 hours.

Humidity deficit (the difference between the maximum and absolute air humidity) is determined using the table of saturated water vapours. The absolute air humidity, calculated using Regnault or Sprung formulas is subtracted from the value of maximum air humidity according to the dry psychrometers thermometer.

Physiological humidity deficit (the difference between the maximum air humidity at 36,5 body temperature and absolute air humidity) is determined using the same table of saturated water vapours (see table 3).

Dew point (temperature when the absolute air humidity is maximum) is determined using the same table of saturated water vapours (see table 3) in reverse direction. The temperature when the absolute air humidity is equivalent to the maximum, is found using the value of absolute humidity.

Interdependency between different air humidity indices can be seen on the diagram (see fig. 6.3).

: : topic6_1: Absolute and maximum air humidity in Hg mm.

Fig. 6.3. Interdependency between different air humidity indices

 

The scheme shows, that the rise of temperature provokes the maximum humidity increase in geometric progression, the absolute humidity in arithmetical progression. When the air temperature rises, the relative humidity is decreases. As a result the amount of water in the air (absolute humidity) is essentially lower in cold seasons than in summer, but is closely related to saturation (maximum humidity). That is why the relative humidity is high in cold seasons and low in summer usually.

The daily temperature, the air humidity and the atmospheric pressure variation are determined using the thermograph, hygrograph and barograph respectively

 

The role of earth surface type in appearing of winds

Wind is air in motion. It is caused by horizontal variations in air pressure. The greater the difference in air pressure between any two places at the same altitude, the stronger the wind will be. The wind direction is the direction from which the wind is blowing. A north wind blows from the north and a south wind blows from the south. The prevailing wind is the wind direction most often observed during a given time period. Wind speed is the rate at which the air moves past a stationary object.

Measuring of wind speed

Plenty of instruments can measure wind.

Wind vane measures wind direction. Most wind vanes consist of a long arrow with a tail that moves freely on a vertical shaft. The arrow points into the wind and gives the wind direction.

: : cup anemometer

 

Anemometers measure wind speed. Most anemometers consist of three or more cups that spin horizontally on a vertical post. The rate at which the cups rotate is related to the speed of the wind. The cup of anemometer has measuring borders from 1 to 50 m/sec, the wing one from 0,5 to 15 m/sec.

Cathathermometer alcohol thermometer with cylindrical or globular reservoir and a capillary tube, dilated upwards, can measure air motion speed from 1,5 to 2 m/sec.

 

Anemometer -

A cup anemometer has metal cups which rotate in the wind.

A swinging-arm anemometer records the force of the wind against a single ball or plate. With a ventimeter wind blows into a hole at the bottom of a tube and raises a plate up it.

A Dwyer wind meter similarly uses a ball. You can easily make a simple anemometer.

: : 7

Fig. Anemometer
U
sage of "wind rose" in preventive sanitary control for settlements, industrial enterprises, resting-places building.

The direction of a wind is determined by that part of horizont from where it blows. A direction and force of wind is taken into account for need of construction and planning of cities. As the direction of a wind is constantly changed, therefore it is necessary to know, what winds dominate in this district. For this purpose all directions of winds on stretch of season or year are taken into account. On this data they create the schedule named "rose of winds". Thus, "rose of winds" represents a graphical image of recurrence of winds.

: : Image3

 

Wind scale

Classification of Wind Speed

Wind speed can be given according to the Beaufort Scale mainly used to report weather at sea, "a force 9 gale" for example. On land, various indicators such as the movement of smoke or branches, enable the wind speed to be estimated with reasonable accuracy.

Force 1: 3 km/h (2 mph) smoke drifts

Force 2: 9 km/h (5 mph) leaves rustle

Force 3: 15 km/h (10 mph) flags flutter

Force 4: 25 km/h (15 mph) small branches move

Force 5: 35 km/h (21 mph) small trees sway

Force 6: 45 km/h (28 mph) large branches move

Force 7: 56 km/h (35 mph) whole trees sway

Force 8: 68 km/h (43 mph) twigs break

Force 9: 81 km/h (50 mph) branches break

Force 10: 94 km/h (59 mph) trees blow down

Force 11: 110 km/h (69 mph) serious damage

Force 12: 118 km/h (74 mph) hurricane damage

 

Wind Projects and Activities

There are lots of projects related to wind speed and direction. You can build a lot of the instruments yourself (look at things to do). Investigate why the wind does what it does!

In enclosed spaces the running speed of air is determined in meters for one second. The more air in a location varies, it is purer and health. But to admit of high speeds of motion of air in a location it is impossible, as flows of cold air, which one acts in a location, can derivate draughts. Is established, that the draught can call in the person or offensive feels or sometimes catarrhal diseases. The feel of a draught is at a running speed of air of 0,5m/sec and above.

Therefore at cooling locations it is undesirable to make motion of air with speed of 0,5m/sec and more, specially in a cold season.

The motion of air near to temperature and damp it influences heat output by an organism and, means, on thermo exchange of the person.

Let's consider such example. Let's allow, that temperature of air high, or is little bit lower from temperature of a human body. The relative humidity is high also. Under such circumstances heat output by a body of the person becomes difficult, as also temperature of air high. Close up to temperature of a human body. The stay of the person in such conditions conducts to an overheating.

Atmospheric pressure

http://www.physicalgeography.net/fundamentals/7d.html

What is Pressure?

Air or atmospheric pressure, is the force exerted on the Earth, by the weight of the air above. That depends on how high the column of air is, so the higher the surface, the less the pressure. That is why you set your barometer to the height of your house or school above sea-level to get correct readings.

Why is it Important?

Different pressure regimes have different types of weather associated with them.

Barometer readings are plotted on a pressure chart. Points on a map that have the same air pressure are connected by lines known as isobars. By studying the patterns shown by isobars, forecasters can make predictions about how the weather will develop. We can identify "troughs" of low pressure and "ridges" of high pressure.

Barometer

http://www.stuffintheair.com/barometermakes.html

Types of barometers

Mercury siphon barometer consists of long vertical tube.Instrument contains mercury. We get the result after summation of hailing mercury tube in long and short knee.

: : mercury barom

Mercury-cupping barometer consists of vertical glass tube which has mercury solder in upper part and open in lower part. Lower part is put into cup with mercury.

Metal barometer aneroid. Main part of this barometer is metal reservoir with cavity. When pressure changes, change volume and forms of reservoir with mercury. http://www.bom.gov.au/info/aneroid/aneroid

: : aneroidbarometer

 

 

: : 6

Fig.Metal barometer aneroid 

 

Barograph.

 

Point of instruments connects with metallic aneroid. The recording barometer may be day and week periodical. To establish of the periodicals it is necessary to open the devices case, to take down from the drums axis for the tape and on its lower part to see on what period well calculated clock mechanism. 747 Millimeter of a mercury column x 4/3 = 963 mB.This quantity we put on the tape instead of the beginning record time.

: : barograph

 

There is a scheme of an estimation of air behind damp: air name dry, when a water pair in this there are less than 55 %, slightly dry at 56 up to 70 %, by slightly wet - from 71 up to 85 %, hardly wet - have more 86 % and saturated - 100 %.

The business in that in miscellaneous terrains prevalence a direction of winds happens miscellaneous. What the dominating direction of winds means? This is a direction, which one often repeats during one year or season.

On meteorological stations permanently registry can be defined a cosines speed of their motion and directions a direction of winds on 4-8 or 16 rhombs. E - Eastern wind, that is wind, that winds from east. W- Western wind; N - Northern wind; S Southern, NE - Northern Eastern. At a sanitarian estimation of the projects of settlements the availability on the schedule of a wind rose enables fast and simplly to orient and to evaluate a regularity of accommodation miscellaneous regions, objects. For example, the regularity of mutual accommodation of industrial firm, which one will flare air of habitation point.

How does the human organism lose a heat?

Major part of heat loses through the skin and mucous, other part goes on heating of food, water and breathes air. Through the skin loses main heat mass: for after one authors - 85-90%, after other - even 95%, so, only 4-6% loses on heating of food, breathe air and waters.

http://www.expeditionsamoyeds.org/Hypothermia.html

Because of that interestingly will learn how the heat is lost by skin. Appear, that skin loses a heat by three ways:

by radiation,

taking and

on evaporation of sweat moisture.

For data of Rubner, we can say, that man attached to light work in room conditions

loses by radiation about 40%,

taking - about 30% and

by evaporation - about 20% of heat.

These ciphers are directed for orientation, and really they consider vacillate dependency on conditions.

 

HEAT TRANSFER,

in physics, process by which energy in the form of heat is exchanged between bodies or parts of the same body at different temperatures. Heat is generally transferred by convection, radiation, or conduction. Although these three processes can occur simultaneously, it is not unusual for one mechanism to overshadow the other two. Heat, for example, is transferred by conduction through the brick wall of a house, the surfaces of high-speed aircraft are heated by convection, and the earth receives heat from the sun by radiation.

Heat Transfer Heat can be transferred by three processes: conduction, convection, and radiation. Conduction is the transfer of heat along a solid object; it is this process that makes the handle of a poker hot, even if only the tip is in the fireplace. Convection transfers heat through the exchange of hot and cold molecules; this is the process through which water in a kettle becomes uniformly hot even though only the bottom of the kettle contacts the flame. Radiation is the transfer of heat via electromagnetic (usually infrared) radiation; this is the principal mechanism through which a fireplace warms a room. Microsoft Corporation. All Rights Reserved.

CONDUCTION

This is the only method of heat transfer in opaque solids. If the temperature at one end of a metal rod is raised by heating, heat is conducted to the colder end, but the exact mechanism of heat conduction in solids is not entirely understood. It is believed, however, to be partially due to the motion of free electrons in the solid matter, which transport energy if a temperature difference is applied. This theory helps to explain why good electrical conductors also tend to be good heat conductors (see Conductor, Electrical). Although the phenomenon of heat conduction had been observed for centuries, it was not until 1882 that the French mathematician Jean Baptiste Joseph Fourier gave it precise mathematical expression in what is now regarded as Fourier's law of heat conduction. This physical law states that the rate at which heat is conducted through a body per unit cross-sectional area is proportional to the negative of the temperature gradient existing in the body.

The proportionality factor is called the thermal conductivity of the material. Materials such as gold, silver, and copper have high thermal conductivities and conduct heat readily, but materials such as glass and asbestos have values of thermal conductivity hundreds and thousands of times smaller, conduct heat poorly, and are referred to as insulators (see Insulation). In engineering applications it is frequently necessary to establish the rate at which heat will be conducted through a solid if a known temperature difference exists across the solid. Sophisticated mathematical techniques are required to establish this, especially if the process varies with time, the phenomenon being known as transient-heat conduction. With the aid of analog and digital computers, these problems are now being solved for bodies of complex geometry.

CONVECTION

Conduction occurs not only within a body but also between two bodies if they are brought into contact, and if one of the substances is a liquid or a gas, then fluid motion will almost certainly occur. This process of conduction between a solid surface and a moving liquid or gas is called convection. The motion of the fluid may be natural or forced. If a liquid or gas is heated, its mass per unit volume generally decreases. If the liquid or gas is in a gravitational field, the hotter, lighter fluid rises while the colder, heavier fluid sinks. This kind of motion, due solely to nonuniformity of fluid temperature in the presence of a gravitational field, is called natural convection. Forced convection is achieved by subjecting the fluid to a pressure gradient and thereby forcing motion to occur according to the law of fluid mechanics.

If, for example, water in a pan is heated from below, the liquid closest to the bottom expands and its density decreases; the hot water as a result rises to the top and some of the cooler fluid descends toward the bottom, thus setting up a circulatory motion. Similarly, in a vertical gas-filled chamber, such as the air space between two window panes in a double-glazed, or Thermopane, window, the air near the cold outer pane will move down and the air near the inner, warmer pane will rise, leading to a circulatory motion.

The heating of a room by a radiator depends less on radiation than on natural convection currents, the hot air rising upward along the wall and cooler air coming back to the radiator from the side of the bottom. Because of the tendencies of hot air to rise and of cool air to sink, radiators should be placed near the floor and air-conditioning outlets near the ceiling for maximum efficiency. Natural convection is also responsible for the rising of the hot water and steam in natural-convection boilers (see Boiler) and for the draft in a chimney. Convection also determines the movement of large air masses above the earth, the action of the winds, rainfall, ocean currents, and the transfer of heat from the interior of the sun to its surface.

RADIATION

Wilhelm Wien German physicist Wilhelm Wien won the 1911 Nobel Prize in physics. His discoveries in the field of radiation, including the laws that govern heat radiation, laid the foundation for the development of the quantum theory. The Nobel Foundation

This process is fundamentally different from both conduction and convection in that the substances exchanging heat need not be in contact with each other. They can, in fact, be separated by a vacuum. Radiation is a term generally applied to all kinds of electromagnetic-wave phenomena. Some radiation phenomena can be described in terms of wave theory (see Wave Motion), and others can be explained in terms of quantum theory. Neither theory, however, completely explains all experimental observations. The German-born American physicist Albert Einstein conclusively demonstrated (1905) the quantized behavior of radiant energy in his classical photoelectric experiments. Before Einstein's experiments the quantized nature of radiant energy had been postulated, and the German physicist Max Planck used quantum theory and the mathematical formalism of statistical mechanics to derive (1900) a fundamental law of radiation (see Statistics). The mathematical expression of this law, called Planck's distribution, relates the intensity or strength of radiant energy emitted by a body to the temperature of the body and the wavelength of radiation. This is the maximum amount of radiant energy that can be emitted by a body at a particular temperature. Only an ideal body (blackbody,) emits such radiation according to Planck's law. Real bodies emit at a somewhat reduced intensity. The contribution of all frequencies to the radiant energy emitted by a body is called the emissive power of the body, the amount of energy emitted by a unit surface area of a body per unit of time. As can be shown from Planck's law, the emissive power of a surface is proportional to the fourth power of the absolute temperature. The proportionality factor is called the Stefan-Boltzmann constant after two Austrian physicists, Joseph Stefan and Ludwig Boltzmann, who, in 1879 and 1884, respectively, discovered the fourth power relationship for the emissive power. According to Planck's law, all substances emit radiant energy merely by virtue of having a positive absolute temperature. The higher the temperature, the greater the amount of energy emitted. In addition to emitting, all substances are capable of absorbing radiation. Thus, although an ice cube is continuously emitting radiant energy, it will melt if an incandescent lamp is focused on it because it will be absorbing a greater amount of heat than it is emitting.

Opaque surfaces can absorb or reflect incident radiation. Generally, dull, rough surfaces absorb more heat than bright, polished surfaces, and bright surfaces reflect more radiant energy than dull surfaces. In addition, good absorbers are also good emitters; good reflectors, or poor absorbers, are poor emitters. Thus, cooking utensils generally have dull bottoms for good absorption and polished sides for minimum emission to maximize the net heat transfer into the contents of the pot. Some substances, such as gases and glass, are capable of transmitting large amounts of radiation. It is experimentally observed that the absorbing, reflecting, and transmitting properties of a substance depend upon the wavelength of the incident radiation. Glass, for example, transmits large amounts of short wavelength (ultraviolet) radiation, but is a poor transmitter of long wavelength (infrared) radiation. A consequence of Planck's distribution is that the wavelength at which the maximum amount of radiant energy is emitted by a body decreases as the temperature increases. Wien's displacement law, named after the German physicist Wilhelm Wien, is a mathematical expression of this observation and states that the wavelength of maximum energy, expressed in micrometers (millionths of a meter), multiplied by the Kelvin temperature of the body is equal to a constant, 2878. Most of the energy radiated by the sun, therefore, is characterized by small wavelengths. This fact, together with the transmitting properties of glass mentioned above, explains the greenhouse effect. Radiant energy from the sun is transmitted through the glass and enters the greenhouse. The energy emitted by the contents of the greenhouse, however, which emit primarily at infrared wavelengths, is not transmitted out through the glass. Thus, although the air temperature outside the greenhouse may be low, the temperature inside the greenhouse will be much higher because there is a sizable net heat transfer into it.

In addition to heat transfer processes that result in raising or lowering temperatures of the participating bodies, heat transfer can also produce phase changes such as the melting of ice or the boiling of water. In engineering, heat transfer processes are usually designed to take advantage of these phenomena. In the case of space capsules reentering the atmosphere of the earth at very high speed, a heat shield that melts in a prescribed manner by the process called ablation is provided to prevent overheating of the interior of the capsule. Essentially, the frictional heating produced by the atmosphere is used to melt the heat shield and not to raise the temperature of the capsule (see Friction).

What is the heat losing way by radiation?

From physics we know, that any more heated body radiates more heat, than less heated. So, even not colliding with it, it gives to it its heat, while the temperatures of both bodies will not complete with each other.

Man in room conditions is usually circled by objects with more low temperature, than his body, that is why takes place heat losing by radiation.

Also heat is lost by installation. In this case a heat is lost by two ways - conduction and convection.

Conduction is a heat transition on the strength of contiguity of objects, and also air parts from more heated to less heated. Convection is a heat transmission on the strength of mediators - air, steam, liquid, the fractions of which, heating attached to contact with more warm body, bear off heat and return it attached to contiguity with more cold objects. On the strength of temperature difference in intermediate environment, for example, in air, the convectional streams are generated.

The third way of heat losing is evaporation of moisture.

A human skin is always covered by sweat, water of which evaporates. For this process it is necessary expenditure of warm /secretive evaporation temperature /.

http://ppo.tamuk.edu/ehs/Heat_Stress/heatstress.htm

 

Microclimate

it is meteorological conditions in work zone, which characterized by complexes of factors that act on organism of peoples it is temperature, humidity and rate movement of air, and also radiation temperature and warm radiation. Temperature of air is favorable factors which influence on heat exchange. Radioactive temperature it is the temperature that surround people of superficiality or intensive sun or another radiation.

Microclimate is a thermal status of the limited space. It results from combined action of air temperature, radiation heat, air humidity and air movement velocity. Microclimate defines heat state of an organism. Microclimate is influenced by latitude, topography, human activities and vegetation as well as other factors. Sometimes they mean microclimate as variations of the climate within a given area, usually influenced by hills, hollows, structures or proximity to bodies of water. The warmth and humidity of the air in close proximity to a plant or heat/moisture source may differ significantly from the general climate of the premise.

Air treatment/air cooling differs from ventilation because it reduces the temperature of the air by removing heat (and sometimes humidity) from the air. Air conditioning is a method of air cooling, but it is expensive to install and operate. An alternative to air conditioning is the use of chillers to circulate cool water through heat exchangers over which air from the ventilation system is then passed; chillers are more efficient in cooler climates or in dry climates where evaporative cooling can be used.

Local air cooling can be effective in reducing air temperature in specific areas. Two methods have been used successfully in industrial settings. One type, cool rooms, can be used to enclose a specific workplace or to offer a recovery area near hot jobs. The second type is a portable blower with built-in air chiller. The main advantage of a blower, aside from portability, is minimal set-up time.

Another way to reduce heat stress is to increase the air flow or convection using fans, etc. in the work area (as long as the air temperature is less than the worker's skin temperature). Changes in air speed can help workers stay cooler by increasing both the convective heat exchange (the exchange between the skin surface and the surrounding air) and the rate of evaporation. Because this method does not actually cool the air, any increases in air speed must impact the worker directly to be effective.

If the dry bulb temperature is higher than 35C (95F), the hot air passing over the skin can actually make the worker hotter. When the temperature is more than 35C and the air is dry, evaporative cooling may be improved by air movement, although this improvement will be offset by the convective heat.

When the temperature exceeds 35C and the relative humidity is 100%, air movement will make the worker hotter. Increases in air speed have no effect on the body temperature of workers wearing vapor-barrier clothing. Heat conduction methods include insulating the hot surface that generates the heat and changing the surface itself. Simple engineering controls, such as shields, can be used to reduce radiant heat, i.e. heat coming from hot surfaces within the worker's line of sight. Surfaces that exceed 35C (95F) are sources of infrared radiation that can add to the worker's heat load. Flat black surfaces absorb heat more than smooth, polished ones.

Having cooler surfaces surrounding the worker assists in cooling because the worker's body radiates heat toward them. With some sources of radiation, such as heating pipes, it is possible to use both insulation and surface modifications to achieve a substantial reduction in radiant heat.

Instead of reducing radiation from the source, shielding can be used to interrupt the path between the source and the worker. Polished surfaces make the best barriers, although special glass or metal mesh surfaces can be used if visibility is a problem.

Shields should be located so that they do not interfere with air flow, unless they are also being used to reduce convective heating. The reflective surface of the shield should be kept clean to maintain its effectiveness.

HVAC (heating-ventilation-air conditioning) system defines indoor microclimate.

A microclimate maintenance system (general HVAC system) created in several rooms gives a possibility to use an economic decision, the idea of which consists in use of one outdoor unit and several indoor units (from two to four). It is explained by the fact that in adjacent rooms air-conditioners have to carry out similar functions of cooling or heating.

This makes it possible to use one outdoor unit for work with indoor units which carry out cooling, for example. As a result such a system has lower operating costs and lower power consumption and at the same time allows you to carry out air-conditioning in one or several rooms, where indoor units are installed.

 

METHOD OF DETERMINATION AND HYGIENICAL ESTIMATION OF NATURAL AND ARTIFFICIAL ILLUMINATION

THE METHODS OF HYGIENIC ESTIMATION OF NATURAL ILLUMINATION.

Spectrum of the Sun Radiation.

Spectrum of the Sun Radiation from the sun is photographed using a spectrometer and is analyzed through the use of a spectrograph. The dark lines in the spectrum are called absorption lines, and are caused by the absorption of radiation by elements in the suns atmosphere. By studying these absorption lines, scientists are able to identify the elements present in the sun. The prominent line at the red end of the spectrum is one of the hydrogen lines and the lines in the yellow indicate the presence of sodium.

Sunlight appears yellowish, but it is actually a combination of a rainbow of colors. Scientists use special instruments called spectrographs to separate sunlight out into its different colors. These instruments do the same thing that water molecules in the atmosphere do when the molecules produce a rainbow. Each color corresponds to a different wavelength of light. Red has the longest wavelength of visible light, and violet has the shortest. The range of wavelengths of sunlight and the intensity at each wavelength are called the Suns spectrum. The study of the spectra of the Sun and other objects or materials is called spectroscopy.

When sunlight is spread out like a rainbow in the Suns spectrum, many dark gaps separate one color from another in the row of colors. These gaps are called absorption lines. Each absorption line is created when sunlight passes through the gases in the Suns photosphere. Atoms and ions of each element in the gas absorb light at certain wavelengths, creating dark gaps in the Suns spectrum.

The dark absorption lines in the spectra of the Sun and other stars fingerprint the ingredients of these stars. Each chemical element produces a unique set of lines, and the presence of these lines shows that a particular element is present in the stellar photosphere. Darker absorption lines indicate greater absorption and therefore larger amounts of the element.

Absorption lines in the Suns spectrum show that hydrogen is by far the most abundant element in the Sun. Other prominent absorption lines are produced by helium, sodium, calcium, and iron. Altogether, 92.1 percent of the atoms in the Sun are hydrogen atoms, 7.8 percent are helium atoms, and the other, heavier elementssodium, calcium, iron, and other elementsmake up only 0.1 percent of the atoms in the Sun. The Suns absorption lines are called Fraunhofer lines, named after German physicist Joseph von Fraunhofer, who cataloged them in the 1800s. The most common Fraunhofer lines are listed below, by the letter Fraunhofer gave them, the color that they block, and the element that causes them.

The Fraunhofer lines designated A and B actually have nothing to do with the composition of the Sun. They only appear on spectra gathered within Earths atmosphere. Earths atmosphere absorbs sunlight at the wavelengths of the A and B Fraunhofer lines, creating dark lines on the Suns spectrum. A spectrum gathered above Earths atmosphere would not have these lines.

The physiological role of daylight inside of house (apartments, room) is that daylight renders a favorable influence on mental condition of the person, especially ill. One the rational lighting has positively effect on a functional state of a cortex of the brain, improves the function of other analyzers. Under the influence of light the metabolism in an organism of the person strengthens, the synthesis of vitamin D is carried out; the processes of a hemopoiesis, the work of closed glands are improved. The mode of lighting plays an essential role in a regulation of biological rhythms. In conditions of intensive lighting the growth and development of the humans organism is improved.

The light intensity of a jobs (works) place has large significance for preventive maintenance of violation of vision. The no rational lighting promotes development of near-sightedness. One to bad or incorrect daylight the mental serviceability is reduced, the fatigue of an organism occurs fast, the coordination of movements is worsened. Besides the daylight is renders a thermal, physiological and bacteriological effect. There fore residential, industrial and public buildings should be provided with daylight.

Owing to a large physiological significance of a visible part of the solar spectrum all locations of preventive establishments which are intended for long stay of patients should have daylight. At a bad daylight (dark time of day, bad weather) the sources of artificial lighting should be used.

The daylight should be steady, with sufficient intensity, not to render for blinding operation, not to create sharp shades.

The daylight in rooms depends on a light climate, which develops on general climatic conditions of locality, degree of an air transparency, echoing properties of an environment.

The orientation of windows has also the relevant significance on also the parties of light defining a insole mode of locations. Depending on orientation of windows three types of insole mode are distinguished.

Types of insulation mode in room

Insular mode of

Orientation windows on the world sides

Time of insulation

(oclock)

% square of room, which insulation

A heat quantity expense at the solar radiation

(kDg/m2)

Maximum

the South-East, the South-West

5-6

80

more 3300

Moderate

the South,

the East

3-5

40-50

2100-3300

Minimum

the North-East the North-West

< 3

< 30

< 2100

The insular mode of locations should be taken into account at patients wards.

In moderate and southern attitudes hospital wards, the room of day time stay should be oriented on the South or South-East, for maintenance of sufficient illuminant and insulation of a place without an overheating.

To the North-up, North-West, North-East are oriented the dressing rooms, rooms for medical procedures , operational, reemission rooms, that ensures a even steady daylight of these places with an indirect lighting and excludes a superheating of rooms blinding effect of sun rays and appearance of a spangle from medical tools.

The lighting depends on distance between buildings height and proximity of green plantations. A denseness of buildings in a district quarter and close disposition of houses to each other leads to a considerable loss of a solar radiation, especially in the lower levels.

The essential factor that influences on intensity and duration of daylight of rooms, is the size, form and disposition of windows. The upper edge of windows is necessary to higher as it is possible. The area of windows should correspond to area of room. Therefore a widespread method of evaluate of a daylight is geometrical, at which one calculate light coefficient (LC), i.e. attitude of a glass area of windows to area of a floor of room. The more size of light factor, the better is lighting. For living rooms LC = 1:6 - 1:8, for hospital wards, the doctors cabinets, educational classes 1:5 - 1:6, for operational, birth wards, observation, dressing rooms, labs 1:3 - 1:4, for extra locations 1:10 - 1:12.

The best in form are the rectangular windows, and the upper edge of the window should be placed from a ceiling on 20-30 cm., for maximum receipt of light to the depth of rooms.

At contamination of glasses the lighting in room decreases on 50-70 %.

The lighting in room is depend on coloring of a ceiling, floor, walls, furniture in the room. The dark colors swallow a plenty of light rays, therefore coloring of locations and furniture at schools, children's preschool and preventive establishments should be brighten. The white color and light tone are mirrored by sun rays on 70-90 %, yellow color - on 50 %, green - on 50-60 %, blue, violet - on 10-11%, black - on 1 %.

The basic lighting engineering parameter for a normalization of a daylight is coefficient of daylight (CDL). This attitude of lighting indoors to simultaneous lighting outdoor, expressed in %. For living rooms CDL must be not less than 0,5 %, for hospital wards - not less than 1 %, for school classes - not less than 1,5 %, for operational - not less than 2,5 %.

The angle of incidence of light rays is an angle between a horizontal surface of a table, and line conducted from this surface to the upper edge of the window. The more erectly direction of light rays, i.e. the more angle, the lighting is more. For living rooms the angle of incidence in norm should be not less than 27.

 

: : 4

Fig. The angle of incidence of light rays

Coefficient of depth(CD ) of room - this is a attitude of distance from the upper edge of the window to a floor to distance from the window to the opposite wall. The hygienic norm CD is no more 2.

 

Description of natural illumination of workplaces

Index

Rates

Coefficient of daylight (CDL)

not less 0,75 %

Light coefficient (LC)

not less 1/6-1/8

Angle of incidence of light rays

not less 27

Angle of opening

not less 5

Coefficient of depth of room(CD)

no more 2

 

The estimation of illumination is made on an illumination level of a horizontal surface on a job place with the help of a luxmeter. An accepting part of the instrument is the photo cell conversing a quantity of light in electrical. A recording part is the sensing galvanometer calibrated in luxs. The obtained result is compared to the established norms.

Appraisal of artificial lighting.

While appreciation of artificial lighting first of all sufficiently of light is measured by directly definition of lighting in lodging. The results are usually compared with well-known hygienic norms. Then one should characterize the light, in particular to indicate whether it is similar to the day light, whether is even, whether it has blinding effect and so on. For answering these questions we have to indicate the kind of light source, the system of lighting, the type of lighting device (chandelier of direct light, of diffused light, of repulsed light, the height of its location, the order of its location, the force of lamps, properties of protective stuff and its ability to make the brightness less. It is also important to establish the presence of shadows on working surface of table; the contact between brightness of working surface and surroundings. Also one have to find whether light sources have blinding effect at the expense of light repulsing from smooth and polishing surfaces and objects. The aim of creating of hygienic norms for lighting is to make the most favourable conditions for eye work. That provides its great working ability and minimal weariness. The functions of eye lights depend of lighting conditions. In sufficient lighting eye can perform its function without stress; on the contrary in irrational lighting eye gets tired very quickly.

Electric Lighting, illumination by means of any of a number of devices that convert electrical energy into light. The types of electric lighting devices most commonly used are the incandescent lamp, the fluorescent lamp, and the various types of arc and electric-discharge vapor lamps .

Neon Lights at Night Bright neon lights shine throughout the night in Las Vegas, Nevada. Neon lamps are used for art, advertising, and even airplane beacons. They are made by evacuating air from glass tubes, then filling them with neon gas. When the light is on, an electric current flows through the gas between two electrodes sealed within the tube. The neon forms a luminous band between the two electrodes.

TECHNOLOGY OF ELECTRIC LIGHTING

Incandescent Lamp In an incandescent lamp, an electric current flows through a thin tungsten wire called a filament. The current heats the filament to about 3000 C (5400 F), which causes it to emit both heat and light. The bulb must be filled with an inert gas to prevent the filament from burning out. For many years incandescent lamps were filled with a mixture of nitrogen and argon. Recently the rare gas krypton has been used because it allows the filament to operate at a higher temperature, which produces a brighter light.

If an electric current is passed through any conductor other than a perfect one, a certain amount of energy is expended that appears as heat in the conductor . Inasmuch as any heated body will give off a certain amount of light at temperatures above 525 C (977 F), a conductor heated above that temperature by an electric current will act as a light source. The incandescent lamp consists of a filament of a material with a high melting point sealed inside a glass bulb from which the air has been evacuated, or which is filled with an inert gas. Filaments with high melting points must be used because the proportion of light energy to heat energy radiated by the filament rises as the temperature increases, and the most efficient light source is obtained at the highest filament temperature. Carbon filaments were employed in the first practical incandescent lamps, but modern lamps are universally made with filaments of fine tungsten wire, which has a melting point of 3410 C (6170 F). The filament must be enclosed in either a vacuum or an inert atmosphere, otherwise the heated filament would react chemically with the surrounding atmosphere. Using an inert gas instead of a vacuum in incandescent lamps has the advantage of slowing evaporation of the filament, thus prolonging the life of the lamp. Most modern incandescent lamps are filled with a mixture of argon or krypton and a small amount of nitrogen.

Radical changes in incandescent lamp design have resulted from substituting compact fused-quartz glass tubes for glass bulbs. These new, stronger-walled bulbs have made tungsten-halogen lamps, a variation of the incandescent lamp, possible. Tungsten-halogen lamps use the regenerative cycle of halogens to return evaporated tungsten particles to the filament, thus extending the life of the bulb. The high temperatures required to take advantage of halogens regenerative cycle made this idea impossible until the walls of the bulb could be made stronger by the introduction of quartz. These bulbs are filled with a mixture of argon and halogen (usually bromine) gases along with a small amount of nitrogen.

TYPES OF LAMPS

Components of a Fluorescent Lamp A fluorescent lamp consists of a phosphor-coated tube, starter, and ballast. The tube is filled with an inert gas (argon) plus a small amount of mercury vapor. The starter energizes the two filaments when the lamp is first turned on. The filaments supply electrons to ionize the argon, forming a plasma that conducts electricity. The ballast limits the amount of current that can flow through the tube. The plasma excites the mercury atoms, which then emit red, green, blue, and ultraviolet light. The light strikes the phosphor coating on the inside of the lamp, which converts the ultraviolet light into other colors. Different phosphors produce warmer or cooler colors.

Electric-discharge lamps depend on the ionization and the resulting electric discharge in vapors or gases at low pressures if an electric current is passed through them . Representative examples of these types of devices are the mercury-vapor arc lamp, which gives an intense blue-green light and is used for photographic and roadway illumination, and the neon lamp, which is employed for decorative sign and display lighting. In newer electric-discharge lamps, other metals are added to mercury and phosphor on the enclosing bulbs to improve color and efficacy. Glasslike, translucent ceramic tubes have led to high-pressure sodium vapor lamps of unprecedented lighting power.

The fluorescent lamp is another type of electric-discharge device used for general-purpose illumination. It is a low-pressure mercury vapor lamp contained in a glass tube, which is coated on the inside with a fluorescent material known as phosphor. The radiation in the arc of the vapor lamp causes the phosphor to become fluorescent. Much of the radiation from the arc is invisible ultraviolet light , but this radiation is changed to visible light if it excites the phosphor. Fluorescent lamps have several important advantages. By choosing the proper type of phosphor, the light from such lamps can be made to approximate the quality of daylight. In addition, the efficiency of the fluorescent lamp is high. A fluorescent tube taking 40 watts of energy produces as much light as a 150-watt incandescent bulb. Because of this illuminating power, fluorescent lamps produce less heat than incandescent bulbs for comparable light production.

One advance in the field of electric lighting is the use of electroluminescence, known commonly as panel lighting. In panel lighting, particles of phosphor are suspended in a thin layer of nonconducting material such as plastic. This layer is sandwiched between two plate conductors, one of which is a translucent substance, such as glass, coated on the inside with a thin film of tin oxide. With the two conductors acting as electrodes , an alternating current is passed through the phosphor, causing it to luminesce. Luminescent panels may serve a variety of purposesfor example, to illuminate clock and radio dials, to outline the risers in staircases, and to provide luminous walls. The use of panel lighting is restricted, however, because the current requirements for large installations are excessive. .

A number of different kinds of electric lamps have been developed for such special purposes as photography and floodlighting. These bulbs are generally shaped to act as reflectors when coated with an aluminum mirror . One such lamp is the photoflood bulb, an incandescent lamp that is operated at a temperature higher than normal to obtain greater light output. The life of these bulbs is limited to 2 or 3 hours, as opposed to that of the ordinary incandescent bulb, which lasts from 750 to 1000 hours. Photoflash bulbs used for high-speed photography produce a single high-intensity flash of light, lasting a few hundredths of a second, by the ignition of a charge of crumpled aluminum foil or fine aluminum wire inside an oxygen-filled glass bulb. The foil is ignited by the heat of a small filament in the bulb. Increasingly popular among photographers is the high-speed gas-discharge stroboscopic lamp known as an electronic flash.

The sources of artificial lighting.

There are two main sources of artificial lighting: incandescent bulbs and luminescent lamp. A bulb is very convenient source of light. Its deficiency is a very small light returning: on 1 Vat of expended electric energy one can receive 10-20 lm. The spectrum of its radiation differs from the spectrum of white daylight. It has less quantity of blue and violet radiation and more red and yellow one. Thats one taking into consideration psycho-physiological side this radiation is pleasant and warm.

Luminescent lamp consists from glass tube. The internal surface of this glass is covered by luminoforum. The tube is full of mercury steam. At the ends it has electrodes. When the lump is switched in the electric net on, the electric current creates between the electrodes. It generates ultraviolet radiation. Under ultraviolet radiation influence luminofor starts to shine. Thus choosing different kinds of luminofor one can made luminiscent lamps with different spectrum of visible radiation: lamps of day light, white light, warm-white light. The spectrum of day light lamp radiation is very clothing by spectrum of natural lighting of lodging, situated on the north. This light helps to get tired less, even if we look at very small subject. To deficiency of lamp one can attribute blue color at surroundings: skin and so on.

Lighting appliance of bulbs.

There are lighting appliance of direct light, reflected light, half-reflected light, and diffused light. The lighting appliance of direct light directs over 90% of lamp light to the lighting place, providing its high lighting. But at the same time there is a great difference between the lighting and sun lighting places of lodging. Harsh shadows are created sometimes it can blind there person. Usually this kind of lighting appliance is used for lighting of auxiliary lodging and sanitary lodgings. The appliance of reflected light is characterised by the fact, that rays from lamp are directed to the ceiling and upper part to the walls. They are repulsed, and evenly, without shadows, are divided in lodging. Their light is soft and diffused. This kind of lighting appliance creates lighting, which exactly corresponds to hygienic norms. But it is not economic one. Because in this case 50% of light is lost. Thats for lighting of settlements, classrooms, wards more economic lighting appliance is used appliance of diffused light. In this case a part of rays shine the lodging after coming through milk or mat glass, and part of rays shine the lodging after repulsing from ceiling and walls. Such lighting appliance creates satisfactory conditions of lighting, does not blind and doesnt create harsh shadows.

Deficiencies of luminiscent lamps (compared with bulbs).

One of the deficiencies of luminiscent lamp is that the skin of people in this light looks very pale or grey. Thats why there lamps are not used in schools, wards and others lodging like these. Becides there are another deficiency. If lighting in case of using luminiscent lamps is power than 750-150 Lk, one can see twilight effect. That means lighting is insufficiently even to look at big object. Thats why while using luminiscent lamps, lighting should be not less than 75-150 Lk. Besides while looking at moving or rotating object in luminiscent lighting sometimes stroboscope effect can occur. That means creating of numerous contours of objects. When dossals are out of order luminiscent lamps radiate pulse light or create noise.

The spectrum of worm-white lamps is rich on yellow and rose rays. This can make the colour of face more pleasant. But at the same time these lamps decrease eye capacity for work. These lamps are used for lighting of railway station, hall, and cinemas, metro stations.

Advantages of luminiscent lamps compared with bulbs.

The bulb cannot be used when one need to differentiate colours well. In this case one should use luminiscent lamp of daylight. Lamps of white light have spectrum rich on yellow rays. Thats why while using true lamps great capacity for eye work is presented, and skin colour looks great. Thats why lamps of white light are used in schools, lecture rooms, settlements, and wards of hospitals. Spectrum of lamps of warm-white light is rich on yellow and rose radiation. This fact makes less capacity for eye work, but makes the skin colour very pleasant. Variety of spectrum is one of the hygienic advantages of these lamps light returning of luminiscent lamps is in 3-4 times higher than light returning of bulbs. Thats why they are more economic. During numerous comparative investigations with bulbs on industrial plants, in schools, hospitals, lecture rooms objective induces, which characterise the nervous system state, weariness of eye, capacity for work almost in all cases prove hygienic advantage of luminiscent lamps. But for their wide usage we need professional help. It is necessary to choose the lamp correctly, according to its spectrum, taking into consideration purpose of the place.

Methods of definition of artificial lighting.

Artificial lighting can be defined by means of calculate methods, for example the methods of middle horizontal lighting. The principle of the methods is the following: if we use 10 Vat of electro energy stress on each square meter of floor, we receive the middle horizontal lighting. It depends on the force of used lamps. While the same expenditure of energy on square unit lighting can be different. It can be explained by different lighting returning of lamps of different force. Using data about lighting while expending energy (10 Wt/m2 ) and taking into consideration that received lighting depends directly on expended energy, one can find artificial lighting. For this we use the quantity of lamps with certain power and quantity of chalendeliers with certain power, which it is necessary for certain lighting. For example, it is necessary to find middle horizontal lighting in classroom. Its floors square is 50 m2. . We also know that 6 chalendeliers are used. The force of each lamp is 200 Wt. The voltage in net is 120 V. Taking into concideration all the conditions, general electro energy force, which is used to shine the classroom is 200 x 6 =1200 Wt. On 1 m2 of floor we have 1200:50 = 24 Wt/m2. For lamps 200 Vat in case of energy expenditure 10 Vat/m2 lighting E will be 35,5 Lk. The lighting will be higher in so many times, as the energy expenditure is higher then common on square unit:

10/24=35,5/E; E = 85,2 Lk.

 

: : 4

 Fig. Luxmeter U-116

 

Proper power (Wt/2) of general illumination

 

Height of hanging of lamps,

Square of the apartment

2

Level of illumination, lux

30

50

75

100

150

200

300

400

500

Luminescence lamp

2-3

10-15

-

-

8,6

11,5

17,3

23

35

46

58

15-25

-

-

7,3

9,7

14,5

19,4

29

39

49

25-50

-

-

6,0

8,0

12,0

16

24

32

40

50-150

-

-

5,0

6,7

10,0

13,4

20

27

34

150-300

-

-

4,4

5,9

8,9

11,8

17,7

24

30

More 300

-

-

4,1

5,5

8,3

11

16,5

22

27

Incandescent lamp (bulb lamp)

2-3

10-15

11

17

24,

31

45

61

-

-

-

15-25

9,2

14

20

25,5

37

50

-

-

-

25-50

7,8

12

17,3

21,5

31

42

-

-

-

50-150

6,5

10,3

14,7

18,5

27

36

-

-

-

150-300

5,6

9,2

12,9

16,3

24

32

-

-

-

More 300

5,2

8,2

12,3

15,3

22

29,5

-

-

-

 

Hygienically norms of artificial illumination

 

Room

Minimal illumination, lx

Luminescence lamp

Incandescent lamp

(bulb lamp)

peration room

-

200

Doctors room

300 (200)

150 (100)

Room for patient

-

50

Study rooms, laboratory room

300

150

Corridor

100

50