Calculation of the thermal state of the body and determination of comfortable microclimatic working conditions
G.V. Fedorovich, A.L. Petrukhin
Calculation of the thermal state of the body and determination of comfortable microclimatic conditions labor.
You can leave your comments, feedback and opinions about the work of the calculator on our website. In chapter .
Work principles detailed in the guide below.
1.1. Purpose of the calculator:- monitoring the state of working conditions of the employee for compliance with applicable sanitary rules and norms, hygienic - establishing the priority of carrying out preventive measures and evaluation of their effectiveness; - drawing up a sanitary and hygienic characteristic of the working conditions of an employee; - analysis of the relationship between changes in the health status of an employee and his working conditions (during periodic medical examinations, a special examination to clarify the diagnosis); - investigating cases of occupational diseases, poisoning and other health problems related to work.
1.2. The calculator can be used:- bodies and institutions of the Federal Service for Supervision of Consumer Rights Protection and Human Welfare in the exercise of control over the implementation of sanitary rules and regulations, hygiene standards in the workplace and social and hygienic monitoring; - organizations accredited to carry out work on the assessment of working conditions; - centers of occupational pathology and occupational medicine, polyclinics and other medical and preventive institutions providing medical care to employees; - employers and employees for information about working conditions in the workplace; - bodies of social and medical insurance.
2.1. Axiomatics. The basic principles of hygienic assessment of microclimate parameters and their connection with the criteria of a person's thermal state are formulated below. The contribution of processes in the body and in the environment to heat exchange at the boundary between them can only be described in terms that are inherent in the heat exchange processes themselves - the temperature of the environment and the surface of the skin, the rate of evaporation of moisture from the surface, etc. Parameters other than those that can be expressed in terms of routine thermodynamic variables should not be used. The reaction of the body can only be a response to the information that it receives from its temperature receptors and only from those places (from the surface of the skin) where these receptors are present. The definitions of heat fluxes and heat balance conditions themselves do not contain estimates of microclimate parameters. Valuation categories are included in the analysis procedure in addition to balance considerations. It should be taken into account that the adaptive mechanisms of the body are very effective and can maintain the heat balance for a sufficiently long time in a wide range of changes in external conditions. Feelings of comfort or discomfort arise as a result of less or more tension in these mechanisms. Quantitative estimates of the degree of intensity of adaptive mechanisms can be based only on those parameters and described in terms that describe the heat transfer processes themselves. Thus, the importance of balance ratios for the heat produced and lost by the body lies in the fact that only the parameters included in these ratios can be used for comparison with subjective assessments of the microclimate.
2.2. Energy consumption: release and loss of energy.Human activity is characterized by several types of released power, :
- The rate of release of total metabolic heat W floor- full energy release due to all sources - chemical processes and muscle activity.
- The rate of release of metabolic heat of the main (background) metabolism in the body w o(≈ 90 W in an adult).
- The rate of release of additional heat associated with the work done W add. It's obvious that W add \u003d W floor - W o
- Mechanical power developed by muscles W fur. The last two values are interconnected by the efficiency of the muscles h = W mech / W extra. Despite some conventionality of the introduction of this coefficient (it varies from person to person, depends on the type mechanical work, the general state of the body, etc.), it is advisable to use it in calculations, while it can be considered equal to ≈ 0.2. Heat rating W tep, released at a certain level of muscle activity, can be obtained from quite obvious ratios
| Wtep = Wo+ Wadd-Wmech = Wo+(1-h)* Wadd. | (1) |
It is this quantity that is included in the heat balance equations, while in normative documents to characterize the category of work in terms of energy consumption (see below paragraph 2.3), the value is used W floor.
1. Category Ia include work with an intensity of energy consumption up to 139 W, performed while sitting and accompanied by slight physical stress (a number of professions in precision instrumentation and engineering enterprises, in watchmaking, clothing production, in management, etc.).
2. Category Ib include work with an intensity of energy consumption of 140-174 W, performed while sitting, standing or walking and accompanied by some physical stress (a number of professions in the printing industry, in communications enterprises, controllers, craftsmen in various types of production, etc.).
3. Category IIa include work with an intensity of energy consumption of 175-232 W, associated with constant walking, moving small (up to 1 kg) products or objects in a standing or sitting position and requiring a certain physical exertion (a number of professions in mechanical assembly shops of machine-building enterprises, in spinning and weaving production and etc.).
4. Category IIb include work with an intensity of energy consumption of 233-290 W associated with walking, moving and carrying loads up to 10 kg and accompanied by moderate physical stress (a number of professions in mechanized foundries, rolling, forging, thermal, welding shops of machine-building and metallurgical enterprises, etc. ).
5. Category III include work with an energy intensity of more than 290 W, associated with constant movement, moving and carrying significant (over 10 kg) weights and requiring great physical effort (a number of professions in blacksmith shops with manual forging, foundries with manual stuffing and pouring of flasks of machine-building and metallurgical enterprises, etc.).
2.4. The main channels of heat transfer.The body can regulate (within certain limits) the intensity of heat loss through various channels and “turn on” them in various combinations, depending on the situation: the intensity of work, environmental parameters, the degree of thermal insulation of the body, etc. (for more details, see).
Lung heat transfer. The physiology of respiration is described in detail in many works (see, for example). Heat and moisture exchange during respiration is a complex process in which the inhaled air is moistened and warmed (or cooled) in the upper respiratory tract, and the exhaled air is dried and cooled (or heated). The process is almost cyclical. Heat loss during respiration is due to deviations from cyclicity - the partial pressure of water vapor in the exhaled air is greater than in the inhaled air, this consumes the latent heat of vaporization. When calculating, you should use a multiple linear regression dependence of the rate of moisture loss during respiration on meteorological parameters (air temperature and humidity) , as well as from the physiological characteristics of the body (respiratory rate, tidal volume), obtained in the work. Recalculation to the parameters directly included in the balance equations is carried out in the book. The dependence of heat loss during breathing Wleg on the intensity of muscle activity and air parameters - temperature ta and absolute humidity aa is determined by the formula: / m 3, γp \u003d 12. The proportion of additional energy release due to muscle activity is denoted by ω: ω = Wadd/Wo , and the function γ(ω) = 1 + ω*(0.5 + ω) interpolates an increase in the rate of pulmonary ventilation with an increase in muscle activity. The value of Wleg should be subtracted from the thermal power Wtherm when calculating heat losses from the body surface. Due to heat exchange at the interface, the skin - inner surface clothes should be given power Wpol - Wleg. Recalculating the power per unit of body surface, we obtain the heat flux density Here S ≈ 2 m 2 - the surface area of the body of an adult. The flow with density Jko should be provided by conductive skin-clothing heat exchange. Conductive heat exchange skin-clothing. The flow Jco of heat through clothing is determined by the temperature difference between the skin tк and the surface of clothing tp and the thermal resistance of clothing Iclo: , where ι = 0.155 °C * m 2 / W is the coefficient for converting conventional units Clo into the actual thermal resistance of clothing. Heat loss from the surface of clothing. Conductive and radiative heat exchange channels operate on the clothing surface. Conductive heat exchange with environment, is proportional to the temperature difference between the surface of clothing and air: here the value of air velocity Va is substituted in units of m/s. Another channel of heat exchange on the surface of clothing is heat exchange due to radiation and absorption of radiant energy. If the density of the radiant energy flux incident on the surface is presented as radiation), then the heat flux from the surface of the clothing will have the form
| Jrad \u003d εpo * σ * (Tp 4 - Trad 4) | (8) |
| Wpot= Kk*S*(1 - RH*exp[ (tv - tk)/ to ]) | (9) |
2.5. Physiological characteristics of the thermal state of the body.
Generalized data on changes in physiological parameters during muscular activity, given in the book, are used. To ensure the normal thermal state of the body, certain relationships must be observed between the intensity of muscle activity (determined, for example, by the magnitude of the mechanical power Wmech or by the value of the total energy release Wpol, unambiguously associated with it by relation (1) and such physiological reactions of the body as the magnitude of moisture loss and the weighted average skin temperature (STC). There are two modes of operation of thermoregulation systems. One of them is “natural” for the body, while the person feels comfortable. The external conditions that ensure such a state are defined as optimal. To ensure a normal temperature regime under non-optimal external conditions, the regulatory systems of the body begin to work with some tension of their capabilities. However, if the external conditions are not too different from the optimum, the voltage of the thermostatic systems is sufficient to maintain the heat balance. The concretization of this qualitative description of the thermal state of the body is given below. Table 1.
Indicators of the thermal state of a person, which are the basis for the development of requirements for the parameters of the optimal microclimate.
| Nature of work | Energy consumption Wpol, W | Moisture loss, Q, g/h | SVTK, °С |
| Light, category Ia | up to 139 | 40-60 | 32,2 - 34,4 |
| Light, category I b | 140-174 | 61-100 | 32,0 - 34,1 |
| Medium, category IIa | 175-232 | 80-150 | 31,2 - 33,0 |
| Medium, category IIb | 233-290 | 100-190 | 30,1 - 32,8 |
| Heavy, category III | 291 - 340 | 120-250 | 29,1 - 31,0 |
The scatter in the values of moisture loss and SVTK is due to the fact that they are related to the range of energy consumed.
Fig.1. The rate of moisture loss corresponding to the comfortable state of the body (middle line) and the allowable voltage of thermoregulation systems (extreme lines).
In Fig.1, the data of Table 1 on the moisture loss of the body are shown in graphical form. Inside the rectangles, according to the data of Table 1, the indicators of the thermal state of a person correspond to comfortable ones. The limits of allowable stresses of the thermoregulation system are determined by the upper and lower straight lines on the plane (W,Q). Outside the boundaries defined by these lines, the thermoregulation systems are overstressed and overheating or hypothermia of the body begins. For calculations, it is possible to use the interpolation of the dependence of the moisture loss Q on energy consumption W of the form Recalculation to the energy spent on sweat evaporation gives a similar formula, where the coefficient K = r * k is 0.26 for the lower limit of permissible values, 0.39 for optimal and 0.61 for the upper limit of permissible values. Similar graphs for the weighted average skin temperature tk depending on the energy consumption Wpol are shown in Fig.2.
Fig.2. The weighted average skin temperature corresponding to the comfortable state of the body (middle line) and the allowable stress of thermoregulation systems (extreme lines).
It can be seen that, in contrast to the rate of moisture loss, which increases with energy consumption, the skin temperature decreases with increasing Wpol. This is quite expected, because. the greater the production of heat, the more intensive should be its removal from the internal parts of the organism to the surface. For this (at a constant temperature internal organs) requires a decrease in skin temperature. For calculations, you can use the interpolation of the dependence of the value of the SVTC on energy consumption Wpol of the form , where the temperature scale t1 is 33.1 °C for the lower limit of permissible values, 35.4 °C for optimal and 36.5 °C for the upper limit of permissible values. For power scale W1, the corresponding values are 2739W, 2185W and 3094W, respectively. If the regulatory capabilities of the heat balance maintenance systems are not enough, the enthalpy (heat content) of the body begins to change. This leads to discomfort, and with large variations in enthalpy - to professionally caused health disorders. For a heating microclimate, the relationship between the excess of enthalpy and the class of working conditions, as well as with a descriptive assessment of the risk of overheating of the body, is presented in Table 2. Table 2.
Harmful effects of excess body enthalpy on the health of workers.
Similarly, the harmful effects of microclimatic conditions increase when the body is overcooled. For a cooling microclimate, the relationship between the enthalpy deficit and the class of working conditions is presented in Table 3. Table 3
Harmful effects of body enthalpy deficiency on the health of workers
Qualitative risk assessment coincides with the data in Table 2 for the corresponding classes of working conditions. The data given in tables 1 - 3, together with the above-described algorithms for calculating the body's heat exchange with the external environment, are the basis for making judgments about working conditions based on the results of measurements of real microclimatic parameters of the production environment.
3. Controlled indicators of the microclimate.
From the ratios given in paragraph 2.4 above, it follows that when studying the thermal state of a person, the following microclimate parameters should be measured:
air temperature Ta;
relative air humidity RH;
air velocity Va;
intensity of thermal irradiation IR;
The relative role of the listed parameters is not the same. The air temperature enters directly into the heat balance equations. The characteristic scale of temperature variations, judging by the data given in Table 1, is several tenths of a degree. This corresponds to a relative uncertainty of ≈ 10 -3 (0.1%) and sets the allowable error of the measuring equipment. Relative Humidity air RH determines the amount of lung heat loss. This value is a small fraction (not more than 25%) of the heat transfer through the conductive heat loss channel, according to formula (2), the relative value of the term proportional to air humidity is not more than 20% of the value of the remaining terms. These circumstances determine the low requirements for measuring relative humidity. An error of 5 - 10% is quite acceptable for measuring relative humidity. The speed of air movement directly determines the coefficient of heat transfer from the surface of clothing according to formula (7). Since the uncertainty of the temperature difference between the air and the surface of clothing can be a few percent, then, accordingly, the requirements are ≈ 5-10% for relative error velocity measurements provide quite sufficient measurement rigor. Estimation of the intensity of thermal exposure introduces the greatest uncertainty into the calculations of the influence of the microclimate on the thermal state of the worker's body. The most reliable way to measure this value is to use a balloon thermometer.
3.1. Measurement of the effective value of thermal exposure.The heat flux due to infrared radiation is a vector quantity. Accordingly, sensors used in measuring instruments can be either directional or isotropic. Almost all devices used in the domestic practice of sanitary and hygienic control are IR radiometers with a limited viewing angle. These devices with directional sensors can be used to measure thermal radiation fluxes from sources with small angular dimensions that fall completely within the field of view of the radiometer. In the case of a large source, or if there are several sources and irradiation occurs from several directions, processing the measurement results is a non-trivial task that does not always have a correct solution. The problem is practically unsolvable for non-stationary (for example, moving) sources. Ball thermometer (Vernon sphere) is an instrument with isotropic sensitivity, most suitable for measuring integral (comprehensive) thermal exposure. The corresponding algorithm for converting the results of temperature measurements into integral thermal exposure is described in. Such a recalculation is based on the heat flux balance equation for the sphere. This value should be used when assessing the thermal state of the body. Relation (16) determines the thermal effect of IR radiation through the well-measured temperatures of the sphere Tg and air Ta, however, it also includes the temperature of the surface of clothing Tc, the measurement of which is much more difficult: it must be measured in several places of clothing with subsequent averaging of the results. Losing somewhat in accuracy, we can replace the temperature Tc in (16) with the air temperature Ta. This leads to a significant simplification of the procedure for monitoring microclimate parameters. The result of such a replacement has the meaning of an effective flow of thermal radiation, it is he who is subject to hygienic rationing.
| ΔJ \u003d ε * σ * (T g 4 -T a 4) + h c * (T g -T a) | (17) |
Thermal irradiation fluxes corresponding to the difference Δt of air temperatures ta and the ball thermometer
|
ta |
10 | 14 | 18 | 22 | 26 | 30 |
| 2 | 24,76 | 25,21 | 25,66 | 26,13 | 26,62 | 27,11 |
| 4 | 49,74 | 50,64 | 51,56 | 52,51 | 53,48 | 54,48 |
| 6 | 74,95 | 76,30 | 77,69 | 79,12 | 80,59 | 82,10 |
| 8 | 100,38 | 102,2 | 104,07 | 105,99 | 107,96 | 109,99 |
| 10 | 126,04 | 128,33 | 130,68 | 133,1 | 135,58 | 138,13 |
| 12 | 151,94 | 154,7 | 157,55 | 160,47 | 163,46 | 166,54 |
| 14 | 178,07 | 181,32 | 184,66 | 188,09 | 191,61 | 195,23 |
| 16 | 204,44 | 208,18 | 212,03 | 215,97 | 220,02 | 224,18 |
| 18 | 231,06 | 235,3 | 239,65 | 244,12 | 248,71 | 253,42 |
| 20 | 257,92 | 262,66 | 267,53 | 272,53 | 277,66 | 282,93 |
| ΔJ \u003d * (T g -T a) | (18) |
4. Selection of clothing as a means of individual protection against the adverse effects of meteorological parameters.
Reasonable recommendations for choosing clothing that ensures comfortable work in real working conditions, are an important point of sanitary and hygienic research in the workplace and production control. Due right choice clothing can significantly improve working conditions and reduce occupational risks without changing the working environment. For this, however, the recommendations must be convincingly substantiated by the results of calculations of the body's heat exchange with the environment.
The materials of items 2-3 indicate that the two main channels of heat exchange with the environment - radiation and conductive - determine the thermal state of the body (see, for example, expression (17) for the heating rate). To determine what PPE should protect against, it is necessary to evaluate the relative role of the mentioned heat transfer channels.
Estimates can be made using relation (16), in which the difference in the fourth powers of temperature is estimated by the difference in the temperatures themselves (see above the transition from (17) to (18)). In other words, when the radiation temperature exceeds the normal room temperature, should be protected from excessive thermal exposure, and at lower radiation temperatures - from overheating or hypothermia of the body due to conductive heat transfer.
4.2. Overalls from heat-reflecting fabric for "hot shops".
Thermal protective clothing provides protection for workers working in hot shops from sparks, scale, splashes of molten metal, radiant heat. The range of such overalls is represented by suits, aprons, mittens, overalls. Linen and cotton fabrics with flame retardant impregnations are used for the production of overalls. Most of these fabrics have a sufficiently dense and smooth surface, from which sparks and splashes of molten metal easily roll off. In order to reflect radiant heat, non-textile materials are used with aluminum coated.
Suits for work in hot shops are made according to GOST 9402-70 (male) and according to GOST 9401-70 (female). The design of these suits can be built on the basis of the design basis of the second and third variants of the first group of workwear products. This type of clothing is intended for workers of various professions (steelmaker, steelmaker's assistant, crane operator, roller operator, boilermaker, pourer, blacksmith, etc.). The suit is used when working in open-hearth, steel-smelting, rolling, foundry-boiler and blacksmith shops, in which the temperature at the workplace reaches + 50 ° C, and the intensity of exposure to radiant heat is up to 18-20 cal / (cm2min).
Reasonable recommendations on the choice of clothing that ensures comfortable work in real-life production conditions are an important point in sanitary and hygienic research during automated workplaces and production control.
By choosing the right clothing, you can significantly improve working conditions and reduce occupational risks without changing the working environment. For this, however, the recommendations must be convincingly substantiated by the results of calculations of the body's heat exchange with the environment. Depending on the goals of such calculations (requirements for microclimate parameters, restrictions on energy consumption, calculation of thermal resistance of clothing, etc.), an algorithm and sequence of analysis of individual heat exchange channels should be selected. The use of a ball thermometer greatly simplifies and refines the calculation of the thermal resistance of clothing that provides individual protection from the adverse effects of microclimatic conditions.
If initially set by the total energy consumption Wpol, for heat transfer calculations, the mechanical power Wmech, heat loss for sweat evaporation Wpot, and heat loss during breathing Wleg should be subtracted from them. The remaining power Wh = Wpol - Wpot - Wleg must be dissipated through clothing. The corresponding heat flux J is given by the formulas:
| J \u003d W h ⁄ S \u003d (t s - t c) ⁄ Iclo | (21) |
Research on the physiology of thermoregulation shows that for each level of energy consumption there is a physiologically determined optimum temperature skin ts, so that if we determine the temperature of the surface of the clothes tc, then from equation (16) we can determine the value of the thermal resistance of clothes Iclo, which provides optimal working conditions with a given total energy consumption Wpol. To determine tc, the heat transfer equation is solved taking into account the conductive and radiative heat transfer channels on the clothing surface: by solving which we determine the temperature Tc of the clothing surface, after which Iclo is determined from (21).
The heat transfer coefficient hg from the surface of the Vernon sphere is determined both by the design of the sphere (its diameter) and the meteorological parameters (air velocity, temperature, etc.). It is possible to choose a sphere for which this coefficient will be equal to the heat transfer coefficient hcc of the clothing surface. In this case, the air temperature Ta is not included in the equation for determining the temperature of the clothing surface Tc - the readings of a ball thermometer are sufficient to determine Tc. This greatly simplifies the calculation of the thermal resistance of clothing that provides comfortable working conditions.
In any case, the use of clothing with correctly calculated thermal resistance is an example of the effective selection of personal protective equipment against the adverse effects of microclimatic conditions. An example of specific calculations demonstrating how much working conditions can be improved in this way is given in the work. It is quite realistic to lower the hazard class by 2-3 points.
5. Algorithms for processing measurement results.
5.1.
The equations given in paragraphs 2-4 can be used to solve various problems related to the optimization of heat exchange between the worker's body and the environment. The results of such calculations lead to a "blurring" of the boundary between the heating and cooling microclimate. It can be shown that, depending on the amount of energy consumption, the quality of clothing and other factors, working in an environment with the same microclimatic parameters can in some cases lead to overheating of the body, and in others to hypothermia. This circumstance is illustrated by the data table 5.
Table 5
Enthalpy build-up rate dH ⁄ dt (kJ ⁄ kg ⁄ hour) when performing work with total energy consumption Wpol (W) performed in clothes with thermal resistance Clo (c.u.)
| Clo Wpol |
0,1 | 0,4 | 0,7 | 1 | 1,3 | 1,6 | 1,9 | 2,2 | 2,5 |
| 100 | -4,39 | -2,03 | -0,62 | 0,33 | 1,01 | 1,52 | 1,92 | 2,23 | 2,49 |
| 120 | -3,67 | -1,27 | 0,17 | 1,13 | 1,82 | 2,34 | 2,74 | 3,06 | 3,33 |
| 140 | -2,88 | -0,44 | 1,02 | 2,00 | 2,70 | 3,23 | 3,64 | 3,97 | 4,24 |
| 160 | -2,00 | 0,48 | 1,97 | 2,97 | 3,68 | 4,22 | 4,64 | 4,97 | 5,25 |
| 180 | -0,98 | 1,54 | 3,05 | 4,06 | 4,79 | 5,33 | 5,76 | 6,10 | 6,38 |
| 200 | 0,20 | 2,75 | 4,29 | 5,32 | 6,06 | 6,61 | 7,05 | 7,39 | 7,68 |
| 220 | 1,58 | 4,18 | 5,74 | 6,79 | 7,54 | 8,10 | 8,54 | 8,89 | 9,18 |
| 240 | 3,23 | 5,86 | 7,45 | 8,51 | 9,28 | 9,85 | 10,30 | 10,65 | 10,95 |
| 260 | 5,19 | 7,87 | 9,48 | 10,56 | 11,33 | 11,92 | 12,37 | 12,73 | 13,03 |
| 280 | 7,54 | 10,26 | 11,90 | 12,99 | 13,78 | 14,37 | 14,83 | 15,20 | 15,50 |
| 300 | 10,35 | 13,11 | 14,77 | 15,88 | 16,68 | 17,28 | 17,75 | 18,12 | 18,43 |
When constructing this table, the following environmental parameters were taken: air temperature ta = 20°C, ball thermometer temperature tg = 23 oC, relative air humidity RH = 50%, air velocity Va = 0.25 m/s, coefficient of absorption of thermal radiation by the surface clothes ε = 0.3, worker weight 75 kg.
It can be seen that when performing even fairly hard work (with energy consumption up to 200 W) in light clothing, the body can become supercooled (dH ⁄ dt< 0), т.е. этот микроклимат будет охлаждающим, но при выполнении работы в одежде с большим термосопротивлением (Clo >1) overheating of the body can be observed (dH ⁄ dt > 0), i.e. the same microclimate should be recognized as heating.
5.2.
The heat balance calculation can be used to select clothing that provides comfort, or at least allowable conditions work. As an example of the results of such a calculation, the data contained in Table 6 can be cited.
In calculations, it was assumed that thermal irradiation leads to the fact that the temperature of the balloon thermometer is 2.5°C higher than the air temperature. The relative humidity of the air was assumed to be 35%, the air velocity Va = 0.25 m/s, the degree of non-blackness of the clothing surface in the IR region of the spectrum ε ≈ 0.2.
Table 6
Thermal resistance (Clo) of clothing that provides optimal and acceptable working conditions with a given energy consumption W (W) at a given air temperature ta (°C)
| 16 | 18 | 20 | 22 | 24 | 26 | |
| 100 | 2,06 | 1,7 | 1,36 | 1,05 | 0,76 | 0,49 |
| 1,66 | 1,31 | 0,99 | 0,69 | 0,41 | 0,16 | |
| 1,3 | 0,97 | 0,66 | 0,37 | 0,11 | <0 | |
| 120 | 1,7 | 1,39 | 1,1 | 0,83 | 0,58 | 0,34 |
| 1,31 | 1,01 | 0,74 | 0,48 | 0,24 | 0,02 | |
| 1 | 0,71 | 0,45 | 0,2 | <0 | <0 | |
| 140 | 1,41 | 1,13 | 0,88 | 0,64 | 0,42 | 0,21 |
| 1,04 | 0,78 | 0,53 | 0,31 | 0,1 | <0 | |
| 0,76 | 0,5 | 0,27 | 0,06 | <0 | <0 | |
| 160 | 1,18 | 0,92 | 0,69 | 0,48 | 0,28 | 0,1 |
| 0,82 | 0,58 | 0,36 | 0,16; | <0 | <0 | |
| 0,56 | 0,34 | 0,13 | <0 | <0 | <0 | |
| 180 | 0,97 | 0,74 | 0,53 | 0,34 | 0,16 | <0 |
| 0,63 | 0,41 | 0,22 | 0,04 | <0 | <0 | |
| 0,4 | 0,19 | 0,01 | <0 | <0 | <0 | |
| 200 | 0,79 | 0,58 | 0,38 | 0,21 | 0,05 | <0 |
| 0,46 | 0,26 | 0,09 | <0 | <0 | <0 | |
| 0,25 | 0,07 | <0 | <0 | <0 | <0 | |
| 220 | 0,62 | 0,43 | 0,25 | 0,1 | <0 | <0 |
| 0,31 | 0,13 | <0 | <0 | <0 | <0 | |
| 0,12 | <0 | <0 | <0 | <0 | <0 | |
| 240 | 0.46 | 0.29 | 0.13 | <0 | <0 | <0 |
| 0.17 | 0,01 | <0 | <0 | <0 | <0 | |
| 0 | <0 | <0 | <0 | <0 | <0 | |
| 260 | 0.32 | 0.16 | <0 | <0 | <0 | <0 |
| 0,04 | <0 | <0 | <0 | <0 | <0 | |
| <0 | <0 | <0 | <0 | <0 | <0 | |
| 280 | 0.18 | <0 | <0 | <0 | <0 | <0 |
| <0 | <0 | <0 | <0 | <0 | <0 | |
| <0 | <0 | <0 | <0 | <0 | <0 |
In table 6, each combination of parameters (W, ta) corresponds to three values of clothing thermal resistance. The average value corresponds to the optimal state of the body: the optimal skin temperature and optimal perspiration (see paragraphs 2-4 above). The extreme values of Clo correspond to the allowable stress of the thermoregulatory systems of the body: the upper one corresponds to the minimum skin temperatures and perspiration, the lower one corresponds to the maximum values of these parameters.
The way to interpret these results can be illustrated by the example of working with 100 W at 16°C (upper left triad in the table). Working conditions in clothes with thermal resistance from 2.06 Clo to 1.3 Clo are acceptable, and if Clo is close to 1.7, the conditions will be optimal. Negative RTDs are not possible for normal clothing, so the corresponding boxes in Table 5 should be interpreted as "narrowing" the ranges of possible clothing RTDs. For example, when working with an energy consumption of 100 W at a temperature of 26 ° C (upper right triad in the table), the permissible conditions are limited by clothing resistances from 0.49 to 0 (no clothing), and clothing with Clo = 0.16 creates optimal working conditions.
With an increase in energy consumption, the permissible thermal resistance of clothing decreases, for example, at W = 200 W and ta = 16 ° C, thermal resistance in the range from 0.25 to 0.79 Clo (optimally 0.46 Clo) is acceptable. At an air temperature of 26 ° C, it is impossible to choose clothes to create acceptable working conditions. Such a microclimate can be called absolutely heating for work with an energy consumption of 200 watts. At ta = 22°C, clothes with thermal resistance up to ≈ 0.2 Clo provide acceptable working conditions, but it is impossible to ensure optimal conditions only by selecting clothing thermal resistance.
5.3.
Operation at low air temperatures can be optimized by using infrared heaters. The selection of the required values of thermal exposure can also be made on the basis of the balance ratios of clause 3.4. The results of the corresponding calculations are shown in Table 7. The calculations assumed: air temperature 12.5°C; relative air humidity RH = 35%; air velocity Va = 0.25 m/s; the degree of non-blackness of the clothing surface in the IR region of the spectrum ε ≈ 0.4.
Data structures in the cells of Table 6 and Table 5. are similar.
The presented data indicate that at low energy consumption (for example, at W = 100 W), the thermal irradiation of a lightly dressed person (Clo ≈ 0.4) should be at the level of 320 W/m2, however, if the thermal resistance of clothing is sufficiently high (Clo ≈ 2.4), additional irradiation is practically not required. For work with high energy consumption (for example, at W = 200 W), additional heating (at the level of 170 W/m2) is required only for lightly dressed workers, but even with clothing thermal resistance Clo ≈ 1, the absence of additional thermal exposure will be optimal. The negative results of calculations of thermal irradiation at high energy consumption indicate the need for additional cooling. For example, if W = 300 W, only light clothing (with Clo< 0,5) может обеспечить допустимые (но не оптимальные) условия труда. Для одежды с большим термосопротивлением работа с W = 300 Вт будет приводить к недопустимому перегреву организма. Единственная возможная защита от перегрева в этом случае - ограничение времени работы, с тем, чтобы дополнительная энтальпия не превышала допустимых величин (см. выше п.2.5).
Table 7
| The intensity of thermal irradiation (W / m 2), necessary to maintain thermal balance when doing work with energy costs W (W) in clothes with thermal resistance Сlo | ||||||
|---|---|---|---|---|---|---|
| 0,4 | 0,8 | 1,2 | 1,6 | 2,0 | 2,4 | |
| W (W) | ||||||
| 100 | 380,33 | 318,97 | 258,11 | 197,76 | 137,89 | 78,51 |
| 319,01 | 257,93 | 197,35 | 137,27 | 77,67 | 18,54 | |
| 263,54 | 202,78 | 142,52 | 82,75 | 23,45 | < 0 | |
| 120 | 360,7 | 289,19 | 218,37 | 148,22 | 78,73 | 9,88 |
| 292,07 | 220,9 | 150,42 | 80,6 | 11,43 | < 0 | |
| 235,19 | 164,38 | 94,24 | 24,77 | < 0 | < 0 | |
| 140 | 340,74 | 259,01 | 178,19 | 98,23 | 19,13 | < 0 |
| 264,8 | 183,49 | 103,06 | 23,5 | < 0 | < 0 | |
| 206,5 | 125,58 | 45,53 | < 0 | < 0 | < 0 | |
| 160 | 319,54< 0 | 227,23 | 136,05 | 45,99 | < 0 | < 0 |
| 236,3 | 144,48 | 53,78 | < 0 | < 0 | < 0 | |
| 176,58 | 85,17 | < 0 | < 0 | < 0 | < 0 | |
| 180 | 295,92 | 192,25 | 90,01 | < 0 | < 0 | < 0 |
| 205,4 | 102,3 | 0,61 | < 0 | < 0 | < 0 | |
| 144,25 | 41,59 | < 0 | < 0 | < 0 | < 0 | |
| 200 | 268,39 | 152,11 | < 0 | < 0 | < 0 | < 0 |
| 170,6 | 54,98 | < 0 | < 0 | < 0 | < 0 | |
| 108,02 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| 220 | 235,2 | 104,48 | < 0 | < 0 | < 0 | < 0 |
| 130,16 | 0,22 | < 0 | < 0 | < 0 | < 0 | |
| 66,15 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| 240 | 194,31 | < 0 | < 0 | < 0 | < 0 | < 0 |
| 82,05 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| 16,6 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| 260 | 143,39 | < 0 | < 0 | < 0 | < 0 | < 0 |
| 23,95 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| < 0 | <0 | < 0 | < 0 | < 0 | < 0 | |
| 280 | 79,87 | < 0 | < 0 | < 0 | < 0 | < 0 |
| < 0 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| < 0 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| 300 | 0,89 | < 0 | < 0 | < 0 | < 0 | < 0 |
| < 0 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| < 0 | < 0 | < 0 | < 0 | < 0 | < 0 | |
6. Literature
1. Timofeeva E.I., Fedorovich G.V. Ecological monitoring of microclimate parameters. M., NTM-Protection, 2007, 212 p.
2. Ivanov K.P. etc. Physiology of thermoregulation. L, Nauka, 1984, 470 p.
3. Krichagin V.I. Principles of an objective assessment of the thermal state of the body. - In the book. Aviation and space medicine (under the editorship of Parin V.V.).-M. 1963. p. 310-314.
4. Breslav I.S., Isaev G.G. (ed). Physiology of respiration - St. Petersburg, Nauka, 1994, 680 p.
5. Ergonomics of the thermal environment - Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria” ISO 7730:2005(E).
6. Hirs D., Pound G., Evaporation and Condensation, (translated from English), IIL, M., 1966.
7. Fedorovich G.V. Microclimate parameters providing comfortable working conditions. // Biot - 2010 - №1 - p.75
The state of the air environment of industrial premises is characterized by the degree of air purity and meteorological conditions - the microclimate of industrial premises.
Microclimate of industrial premises - m meteorological conditions of the internal environment of these premises, which are determined by the combinations of temperature, humidity, air velocity and thermal radiation acting on the human body.
Prolonged exposure of a person to unfavorable meteorological conditions sharply worsens his state of health, reduces labor productivity and often leads to various diseases.
Requirements for the parameters of the industrial microclimate are established by GOST 12.1.005-88 "General sanitary and hygienic requirements for the air of the working area" and SanPiN 2.2.4 548-96 "Hygienic requirements for the microclimate of industrial premises".
Hygienic requirements for indicators of the microclimate of workplaces of industrial premises are established taking into account the intensity of energy consumption of workers, the time of work, the period of the year.
Microclimate indicators should ensure the preservation of the heat balance of a person with the environment and the maintenance of an optimal or acceptable heat balance of a person.
To assess the acclimatization of the human body at different times of the year, the concepts of cold and warm periods of the year are introduced.
Cold period of the year- the period of the year, characterized by an average daily temperature of the outside air, equal to + 10 degrees C and below.
Warm period of the year- the period of the year, characterized by an average daily temperature of the outside air above + 10 degrees C.
When taking into account the intensity of labor, all types of work, based on the total energy consumption, are divided into 3 categories: light, moderate and heavy.
Moderate physical work(category II) - activities with energy consumption in the range of 151-250 kcal / h (175-290 W).
Category Ib includes work performed while sitting, standing or walking and accompanied by some physical stress (work related to the maintenance of communication equipment).
Category IIa includes work associated with constant walking, moving small (up to 1 kg) objects in a standing or sitting position and requiring a certain physical exertion (work in mechanical assembly shops, spinning and weaving production).
Category IIb includes work associated with walking, moving and carrying loads up to 10 kg and accompanied by moderate physical stress (work in blacksmith shops, thermal, welding shops).
Category III includes work associated with constant movement, moving and carrying significant (over 10 kg) weights and requiring great physical effort (a number of works in forges and foundries).
Optimum or acceptable microclimate conditions must be provided at workplaces.
Optimal microclimatic conditions established according to the criteria for the optimal thermal and functional state of a person. They provide a general and local feeling of thermal comfort during an 8-hour work shift with minimal stress on thermoregulatory mechanisms, do not cause deviations in health status, create prerequisites for a high level of performance and are preferred in the workplace.
Optimal microclimatic conditions must be observed at the workplaces of industrial premises, where operator-type work is performed, associated with neuro-emotional stress.
Permissible microclimatic conditions established according to the criteria for the permissible thermal and functional state of a person for the period of an 8-hour work shift. They do not cause damage or health problems, they cannot lead to general and local sensations of thermal discomfort, tension in the mechanisms of thermoregulation, deterioration in well-being and a decrease in efficiency.
Permissible microclimatic conditions are established in cases where, due to technological requirements, technical and economically justified reasons, optimal values of microclimate indicators cannot be provided.
|
Period of the year |
Air temperature, deg С |
Relative humidity, % |
Air speed, m/s |
||||
|
Optimal conditions |
Permissible conditions |
Optimal conditions |
Permissible conditions |
Optimal conditions |
Permissible conditions |
||
|
Cold | |||||||
When ensuring optimal and acceptable microclimate indicators in the cold season, it is necessary to use means to protect workplaces from radiation cooling from the glass of window openings, and in the warm season - from direct sunlight.
Heating microclimate- a combination of microclimate parameters (air temperature, relative humidity, air velocity and thermal radiation), in which there is a violation of heat exchange between a person and the environment, which is expressed in the accumulation of heat in the body above the upper limit of the optimal value.
To assess the heating microclimate, an integral indicator is used - the thermal load of the environment (THS - index).
THC is an integral index, expressed in degrees, reflecting the combined effect of air temperature, air velocity, humidity and thermal radiation on heat exchange between a person and the environment.
THC - the index is measured by devices such as bolometers, electrothermometers.
Cooling microclimate- a combination of microclimate parameters, in which there is a change in the body's heat transfer, leading to a deficiency of heat in the body.
The class of heat conditions when working in industrial premises with a cooling microclimate is determined by the lower value of the temperature of industrial premises.
In industrial premises, in which it is impossible to establish acceptable conditions for microclimate parameters due to technological requirements for the production process or economically justified inexpediency, microclimate conditions should be considered as harmful and dangerous. In order to prevent the adverse effects of the microclimate, protection of workers from possible overheating and cooling should be provided:
Local air conditioning systems;
Air showering;
Room for rest and heating;
Overalls and other PPE;
Regulation of work time, in particular breaks in work, reduction of the working day, increase in the duration of vacation, reduction of work experience.
Optimum microclimate parameters in industrial premises are provided by air conditioning systems, and acceptable microclimate parameters are provided by ventilation and heating systems.
Working conditions are based on an analysis of the working environment within which the activity is carried out. There are 3 states of a person that affect the quality of work and health: normal, borderline, pathological. All categories of severity of work performed have their own characteristics, since each has certain characteristics.
The above states of the body are manifested in physical and mental labor. And this applies to favorable and unfavorable spheres. In production conditions, depending on factors, one state may prevail. Therefore, they are used to determine the category of severity of work.
Category types
On the basis of medical and physiological work, the categories of severity of the work performed were identified. By the number of them, 6 turned out, and each is characterized by its own properties:
- type of work carried out in a normal environment with a favorable physical, mental and neuro-emotional load: in this case, the health and performance of the employee is preserved;
- assumes the compliance of environmental conditions with hygienic standards: in this case, there is a correspondence of conditions to acceptable production factors;
- with this type of work, the muscular, neuro-emotional state worsens due to not entirely favorable working conditions;
- this includes work performed in adverse conditions, which causes the onset of a pathological condition;
- a person performs such work, due to which, under the influence of negative conditions, pathological reactions appear;
- such reactions occur after the start of the working period, such as a shift.
The concept of heaviness and tension
Categories of severity of work performed are associated with other concepts. Their relationship determines the level of activity. The severity of labor is called the involvement of muscles and physiological costs due to stress. And tension is the reaction of the nervous system to various modes of work. With the help of these concepts, the conditions of activity are formed.
The terms can be applied to mental and physical labor, as well as to various. This also applies to hazardous working conditions.
How to prevent fatigue and overwork?
To prevent fatigue and improve performance, you need to use simple exercises and workouts. Whatever the categories of severity of the work performed, GOST includes the need for simple measures.
Fitness is a state of the body that appears due to the constant performance of work tasks, which is the reason for improving performance. Therefore, its implementation allows you to normalize any type of work. Exercises are part of a workout that, through repetition, restore performance in different activities.
In order to avoid fatigue, a reduced duration of the work shift is used. Also, for this, mechanization, automation, and the principles of the correct labor process are used. Such measures must always be used, whatever the category of severity of the work performed. involves the use of effective techniques necessary to protect workers from fatigue.
Health change
Subject activity is divided into 3 phases:
- 1st is 30-60 minutes: a person gets used to work, but mistakes can be made, gradually the duration of this stage decreases;
- 2nd lasts several hours: increased human performance;
- on the 3rd, fatigue sets in, which reduces productivity and the quality of work, which requires a break to recuperate.
With the help of rest, which is specified in the legislation, a person improves well-being. After that, he is ready to work again. Any category of severity of work performed, a driver, for example, or a person of another profession, requires periodic breaks.
Functions of the severity of labor during the passage of the ITU
A specific category of severity of work performed for the ITU is assigned under the supervision of specialists. In the presence of certain types of ailments, loads are prohibited, or they are only limited, otherwise you can harm human health.
The severity category of work performed for VTEK is approved based on the activities and costs required for the work. Often, additional costs deplete the body. Many diseases become the cause of physical suffering of a person, because of which a pain syndrome develops.
Mode of work and rest
For each employee, it is important to observe the regime of work and rest. This is necessary for maintaining health and increased performance. For example, if employees take breaks throughout the day, the onset of fatigue will slow down.
Performing monotonous work is dangerous because:
- that the resistance of the immune system is deteriorating;
- irritability appears;
- pathologies of the heart and blood vessels occur.
Reduces fatigue competent organization A break is required when eating, to change activities. The regime must be observed on the basis of the main task of the schedule is to improve the results, as well as reduce the phases of fatigue.
Breaks for rest should be determined depending on the Employees need some time before lunch, as well as after. The duration of such a rest is 10-15 minutes. If people are busy with difficult work, then breaks should be every hour for 5 minutes.
40-60 minutes are given for eating. These rules are fixed in the work schedule. In its creation, several features are taken into account. The total time needed to take a break from heavy activity is 4-20%. For knowledge workers, rest should last about 10% of working time. These rules are written into the law. It should be borne in mind that regulated rest is considered effective. Irregular breaks, as well as downtime, disrupt the rhythm of work.
Types of recreation
Rest can be passive or active. The first is necessary when employed in hard work. This is especially true when a person is standing for a long period. Active recreation is offered to people with a sedentary job. For this, gymnastics is used, which includes a set of exercises. With the help of outdoor activities, vitality is quickly restored, which is associated with a change in activity.
Each company may have its own working hours. The regime can be shifted, monthly, daily, weekly, annual. Compliance with the necessary standards allows the company to work efficiently, and employees always be healthy.
Industrial premises. (SanPiN 2.2.4.548-96)
Table 3.3
Permissible microclimate parameters at workplaces
industrial premises
| Period of the year | Category of work according to the level of energy consumption, W | Air temperature, 0 С | Surface temperature, 0 C | Relative humidity, % | Air speed, no more than m/s | ||
| Range below optimal values | Range above optimal values | For the range of air temperatures below the optimum values, no more | For the air temperature range above the optimum values, no more | ||||
| Cold | 20,0-21,9 19,0-20,9 17,0-18,9 15,0-16,9 13,0-15,9 | 24,1-25,0 23,1-24,0 21,1-23,0 19,1-22,0 18,1-21,0 | 19-26 18-25 16-24 14-23 12-22 | 0,1 0,1 0,1 0,2 0,2 | 0,1 0,2 0,3 0,4 0,4 | ||
| Warm | 1a (up to 139) 1b (140-174) 2a (175-232) 2b (233-290) 3 (more than 290) | 21,0-22,9 20,0-21,9 18,0-19,9 16,0-18,9 15,0-17,9 | 25,1-28,0 24,1-28,0 22,1-27,0 21,1-27,0 20,1-26,0 | 20-29 19-29 17-28 15-28 14-27 | 15-75 15-75 15-75 15-75 15-75 | 0,1 0,1 0,1 0,2 0,2 | 0,2 0,3 0,4 0,5 0,5 |
Permissible values of the intensity of thermal exposure of workers from radiation sources heated to white and red glow (hot or molten metal, glass, flame, etc.) should not exceed
140 W/m2.
In this case, no more than 25% of the body surface is exposed to radiation, and the use of personal protective equipment, including the face and eyes, is mandatory.
In the presence of thermal exposure, the category of work is taken into account, therefore, when performing light work, temperatures up to 25 0 C are allowed. The characteristics of work in terms of energy consumption are given in Table. 3.4.
The characteristics of industrial premises by category of work performed, depending on the energy consumption, should be established in accordance with departmental regulations from the category of work performed by 50% or more of workers in the corresponding room. The working area is considered to be a space limited by a height of 2 m above the floor level or a platform on which there are places of permanent or temporary stay of workers.
Table 3.4
| Work | Category | Energy consumption of the body (energy consumption during work) | Job Description |
| Light physical | No more than 150 kcal/h (174 W) | ||
| 1a | No more than 120 kcal/h (139 W) | Work performed while sitting and accompanied by slight physical stress (a number of professions in precision instrumentation and engineering enterprises, in watchmaking, clothing production, in management, etc. | |
| 1b | 121-150 kcal/h (140-174 W) | Work performed while sitting, standing or walking and accompanied by some physical stress (a number of professions in the printing industry, communications enterprises, controllers, craftsmen in various types of production, etc.) | |
| Physical Moderate | 151-250 kcal/h (175-232 W) | ||
| 2a | 151-200 kcal/h (175-232 W) | Works associated with constant walking, moving small (up to 1 kg) products or objects in a standing or sitting position and requiring a certain physical exertion (a number of professions in mechanical assembly shops of machine-building enterprises, in spinning and weaving, etc.) | |
| 2b | 201-250 kcal/h (223-290 W) | Works associated with walking and carrying weights up to 10 kg and accompanied by moderate physical stress (a number of professions in mechanized, foundry, rolling, forging, thermal, welding shops of machine-building and metallurgical enterprises, etc.) | |
| hard physical work | More than 250 kcal/h (290 W) | Works associated with constant movement, moving and carrying significant (over 10 kg) weights and requiring significant physical effort (a number of professions in blacksmith shops with manual forging, foundries with manual stuffing and pouring of machine-building and metallurgical enterprises, etc.) |
Permanent workplace - a place where the employee is most of his working time (more than 50% or more than 2 hours continuously). If at the same time work is carried out in various points of the working area, the entire working area is considered a permanent workplace.
A non-permanent workplace is a place where an employee spends a smaller part (less than 50% or less than 2 hours continuously) of his working time.
In industrial premises where the permissible normative values of the microclimate cannot be maintained according to technological requirements or it is not economically feasible, the microclimate conditions should be considered as harmful and dangerous.
In these cases, protective measures are used, for example, local air conditioning systems, overalls, rooms for rest and heating are equipped, working hours are regulated, i.e. breaks in work are established, the duration of work is reduced, vacations are increased, the length of service is reduced, etc.
To assess the overall impact of microclimate parameters on the possibility of overheating of workers, it is recommended to use the integral indicator of the thermal load of the environment (TNC), which is an empirical indicator that characterizes the overall impact on a person of temperature, relative humidity, air velocity and thermal exposure.
TNS-index is calculated according to the equation:
TNS=0.7 t vl +0.3 t w, (3.1)
where t vl – wet bulb temperature, 0 С; t w is the temperature inside the blackened sphere, 0 С.
t vl is determined by an aspiration psychrometer; t w is measured with a thermometer, the reservoir of which is placed in the center of the blackened ball. This temperature reflects the influence of air temperature, surface temperature and air velocity.
Table 3.5
The most accurate device for measuring relative humidity is an aspiration (ventilation) psychrometer (Fig. 3.1). Includes: two thermometers 1 and 2 which are protected on the sides from thermal radiation and mechanical damage by nickel-plated grooves. Thermometer tanks are surrounded by double nickel-plated sleeves (tubes) 4 and 5 through which air passes at a constant speed (4 m/s). Air movement is achieved by means of a fan 6 and connecting tube 7 . The fan is driven by a spring, which is wound by a key 8 , the presence of metal tubes in the psychrometer 4 , 5 with an air gap between them protects the tanks of thermometers from thermal radiation, and the relatively high speed of air movement near the tank reduces the time to establish temperature equilibrium and ensures a stable evaporation mode, regardless of the speed of the surrounding air. With the help of psychrometers, the relative humidity of the air is determined at temperatures up to - 5 ° C. If the temperature is lower, then hygrometers are used.
Rice. 3.1. Aspiration psychrometer
The air flow rate is determined by cup and vane anemometers.
The vane anemometer consists of a metal case in which a wheel with blades and a counting mechanism are mounted connected to the wheel axle. The counting mechanism has several hands and a dial, the divisions of which correspond to the meters of the path. To turn the counter on and off, there is a lever, the so-called arrester. In a cup anemometer, the receiving part is a small cross with four hollow hemispheres facing the convex surfaces in one direction. Cross with hemispheres under the action of the air flow moves towards the convexity of the hemispheres. The rotation of the crosspiece is transmitted to the counting mechanism.
The vane anemometer is used to determine the air flow velocity from 0.5 m/s to 16 m/s, the cup anemometer is used to measure air velocity from 9 m/s to 20 m/s. Velocity less than 0.5 m/s is measured by electric anemometers.
Microclimate control is carried out in accordance with the requirements of San PiN 2.2.4.548-96, for which thermometers, psychrometers, anemometers and actinometers are used.
Temperature and relative humidity are measured by aspiration psychrometers, air velocity is measured by electrothermoanemometers, cup and vane anemometers, heat flow intensity is measured by actinometers.
Actinometers are a block of thermocouples connected to a galvanometer, which is calibrated in cal / cm 2 × min or W / cm 2.
The surface temperature is measured by contact (such as electrometers) or remote (pyrometers, etc.) devices.
3.2. HEATING AND AIR CONDITIONING
INDUSTRIAL PREMISES
To maintain the required air temperature during the cold season, heating is used in the premises, which, depending on the coolant, can be water, steam and air. Hot water for heating can be supplied from a private boiler house or from a central boiler house. Steam for heating is used in cases where it enters the room for technological needs. The air is heated by radiators or steel pipes through which hot water or steam moves. Pipes are used in rooms with high dust emission, as they are easy to clean from dirt. Heating appliances must not lead to the evaporation of toxic or flammable substances. In terms of fire, the water system is safer, since the water temperature is 40-60 ° C, and the steam temperature is 120-150 ° C, which in some cases can lead to spontaneous combustion of dust.
For air heating, heaters are used, which consist of sections of steel pipes or electric heaters. In the first case, the heat of steam or water is used, in the second - electricity. The fan circulates air through the radiator of the heater, after which it enters the room. In factories and warehouses where there are substances that react with water, air heating with electric heaters is used. To protect the premises from cold air, thermal curtains are installed near the gates, while warm air from the heaters is supplied along the gate line.
The purpose of air conditioning units is to maintain the meteorological conditions (microclimate) in the premises within the specified limits and to fulfill some special requirements. There are two types of air conditioners:
* installations of complete air conditioning, when temperature, relative humidity, air velocity and some special requirements are maintained within specified limits, such as deodorization (elimination of unpleasant odors);
* partial air conditioning units provide only a part of these parameters.
The air conditioner consists of the following main parts (Fig. 3.2.):
I - compartment where outside air is mixed with recirculation. Recirculation is used at low outdoor temperatures, while the air from the room is not emitted into the atmosphere, but partially enters, after being cleaned, back into the room. Recirculated air must not contain harmful impurities. The air entering the compartment I is cleaned by a filter 1 and, if necessary, heated by a heater 2 ;
II compartment - washing chamber, where the air is humidified and, if necessary, cooled by spraying water from the nozzles 3 ;
III section of the second heating, where the air is heated by a heater 4 to achieve the required temperature and relative humidity values.
Rice. 3.2. Air conditioning circuit
Air conditioning is used both to maintain the specified limits of the microclimate, and according to the requirements of the technological process, if the latter do not allow significant fluctuations in the temperature regime.
3.3. REGULATION AND CONTROL OF HARMFUL SUBSTANCES
WORKPLACES
Rationing of harmful substances is carried out in accordance with GOST 12.1.005-88 "General sanitary and hygienic requirements for the air of the working area" and GN 2.2.5.1313-03 "MAC of harmful substances in the air of the working area", which gives the maximum permissible concentrations of 1307 types of harmful substances . The maximum permissible concentration (MPC) is considered to be such a concentration that does not cause diseases or deviations in the state of health during the entire length of service.
Harmful substances released during production processes affect the human body in different ways, i.e. their nature of action is different. Substances can be: general toxic, causing poisoning of the whole organism; irritant, causing irritation of the respiratory tract; carcinogenic, causing cancer; mutagenic, leading to a change in heredity; substances that affect reproductive (childbearing function).
Harmful substances according to the degree of impact are divided into the following classes:
1 - extremely dangerous;
2 - highly dangerous;
3 - moderately dangerous;
4 - slightly dangerous.
GOST also indicates the state of aggregation of a substance under production conditions in the form of an aerosol or vapor. The features of the action on the body are also indicated.
For example, maximum concentration limit for silicon dioxide is 1mg/m 3 .
With the simultaneous content in the air of the working area of several harmful substances of unidirectional action (according to the conclusion of the State Sanitary Inspection), the sum of the ratios of the actual concentrations of each of them (K 1 , K 2 , ... K n) in the air to their MPC (MPC 1 , MPC 2 , ... MPC n) should not exceed unity.
In production, the air environment is systematically monitored to determine the degree of contamination with gases and aerosols. The amount of aerosol in the air (dust, smoke, fog) is determined by weight and various physical methods. Of the physical methods, light is more often used, when the amount of aerosol is judged by the attenuation of the beam of light passing through the aerosol. However, in practice, as a rule, the gravimetric method is used, although it is the most laborious and time consuming at low impurity concentrations. With the weight method, a certain volume of air is drawn through special filters, and the concentration of the aerosol is determined by the difference in the weight of the filters before and after the air is pulled.
The gas component of impurities is determined by express and laboratory methods. With the express method, a certain volume of air is drawn through an indicator tube, which is filled with a reagent that changes color when interacting with a certain gas, and the concentration of this impurity is estimated along the length of the reagent column that has changed color. In laboratory methods for determining the gas component, chromatographs, spectrophotometers, and various special devices are used.
3.4. TYPES OF INDUSTRIAL VENTILATION
Ventilation is the organized supply and removal of air from industrial premises.
Purpose of ventilation:
Removal of harmful gases, vapors, dust from working premises;
Removal of excess heat and moisture emissions, i.e. creation of a normal microclimate;
Supply of clean air to the premises and workplaces;
Collection and disposal of substances removed from the premises.
According to the principle of air movement, ventilation is divided into natural (aeration) and mechanical. Mixed ventilation uses natural and mechanical ventilation. By appointment, ventilation is divided into supply and exhaust. According to the place of action, ventilation is divided into general and local. General or general exchange ventilation is designed to exchange air throughout the room. Local ventilation is designed to remove polluted air directly from the sources of its formation and supply clean air to workplaces. In production, as a rule, general ventilation is used, and to remove dust from sources of formation - local ventilation, for example, when grinding, sharpening.
In addition, air showers, air thermal curtains, local suctions, such as side suctions of galvanic baths, are used.
One of the characteristics of ventilation of industrial premises is the rate of air exchange, which is determined by the formula:
where V vent - the volume of air supplied to the room by ventilation systems during an hour, m3 / h; V pom is the volume of the room, m3.
The air exchange rate shows how many times during an hour the entire volume of air inside the room changes.
natural ventilation
The natural inflow of air through non-densities in walls, window sashes in building exterior structures of buildings and structures, as well as through the pores of materials is called air infiltration. The natural removal of air is called air exfiltration. Infiltration and exfiltration organize a certain air exchange in the room that is not determined by the calculated data.
The natural removal of air from the room to the outside and its entry inside are carried out under the influence of wind and the difference in the densities of the outdoor and indoor air. The density difference is created by the temperature difference between the outside and inside air.
On the windward side of the building, the air pressure is greater than inside the building and the air enters the room. When the wind blows over a building, the wind, encountering an obstacle in the form of a building on its way, slows down, changes its direction and smoothly flows around the building. At the same time, a rarefaction is created on the windward (leeward) side of the building and on the roof - low pressure. And the air comes out of the room.
Thus, due to the pressure difference, the air from the windward side enters all openings and all the gaps in the building structures into the room.
Through all non-densities, the air from the windward side of the building leaves the room to the outside.
Such natural air exchange is called ventilation (draft) or unorganized air exchange.
Outdoor air infiltration increases the cost of heating it.
Exfiltration of indoor air during the cold season moistens the outdoor fences and reduces their heat-shielding properties.
In the general case, natural air exchange in industrial premises with significant excesses of sensible heat occurs under the influence of the temperature difference between the indoor and outdoor air and the action of the wind.
Organized natural air exchange is called aeration. With aeration, air exchanges can reach millions of cubic meters per hour. In winter, aeration allows you to create 20-fold air exchange, in the warm period 50-fold air exchange.
Aeration is arranged in shops with large heat excesses of at least 100 kcal / m 3 .h .: open-hearth, rolling, electric steel-smelting shops, forges, thermal, sheet-rolling and conveyor foundries, etc. The width of the shop should not exceed 80 m.
Aeration can function with mechanical ventilation: local exhaust and supply units. Combined aeration: natural supply, mechanical exhaust or mechanical supply, natural exhaust.
Aeration is carried out through adjustable openings in the outer enclosures.
On fig. 31 shows a diagram of the aeration of a single-span shop.
Fig.31. Organization of natural air exchange:
a - wind flow around the building; b - aeration of a single-span workshop: 1 - warm period of the year; 2 - cold period of the year.
In the warm period of the year, when the average daily outdoor temperature is above +10 degrees, outdoor air enters the room through openings in the lower part of the building. The distance from the finished floor mark to the bottom of the opening is not more than 1.8 m.
In the cold season, when the average daily outdoor temperature is +10 degrees. and below, outdoor air enters the rooms through the upper openings. In this case, the cold outside air entering the working area is heated and reaches it with the calculated parameters.
Air is removed from the workshop through openings in the upper part of the room. If the building has a lantern, then the air is removed through the lantern transoms. In the absence of a lantern on the building to remove air, exhaust shafts are arranged or roof fans are installed. Air can also be removed through deflectors.
Under the action of the wind, the air entering the building from the windward side overturns the circulation flows from the upper zone into the working zone, which have absorbed heat, dust, gases: at the same time, the sanitary and hygienic indicators in the working zone deteriorate.
To regulate natural air exchange, depending on the direction and action of the wind, the areas of supply and exhaust openings should be regulated, which is not possible from an operational point of view.
To prevent wind from blowing into the room, wind shields are installed in front of the exhaust openings on the lantern. A shield installed in front of the lantern opening creates a vacuum on its wings and the air leaves the room in all cases.
Non-blown lanterns were also developed, for example, a lantern designed by V.V. Baturin.
Rice. 32. Lantern designed by V.V. Baturin
During aeration, natural air exchange is determined by the difference in the densities of the external and internal air. Outside air, being denser, enters the room through the lower openings. It heats up in the room and is removed from it through the upper openings.
A thermal jet arises above any heat source. The air adjacent to the source is heated from it and rises. Instead of the air rising up, new volumes of air continuously flow to the heat source in its place. Above the heat source, a thermal jet is formed, directed upwards into the room. The heat jet reaches the ceiling and spreads over it in all directions.
On the one hand, supply jets enter the room, on the other hand, convective jets appear above the heat sources. Air flows into the room.
As a result of cooling and for supplying heat and supply jets, part of the air returns from the upper zone down, and a part equal to the inflow is removed outside.
It has been established that if the ceiling is dismantled near the room, then in this case the air from the upper zone will return to the lower zone to feed the jets and will not completely leave the room.
The figure shows the flow patterns during aeration of one, two and three span shops. In two span shops, outside air enters the shop through side openings, interacts with convective flows and exits through openings in the lantern.
In the three bay halls, of which the middle bay is cold and has a lower height, air enters the middle bay and is distributed to the hot bays. Air is removed through the holes in the lanterns of hot shops.
Rice. 33. The movement of air flows during aeration:
a - one span shop; b - two span shop; in - three span shop.
At the same time, there is another qualitative picture of natural air exchange, in particular, I.A. Shepelev (Fig. 34).
In an aerated room, air is stratified along the height. There are two zones: the lower one, fed by cold outside air, and the upper one, fed by convective currents rising above the heated equipment. The resulting stratification of air is called "temperature overlap". Temperature and concentration jumps occur at the level of temperature overlap. The reason for the overlap is the oncoming movement of air fronts: the front of supply jets and the front of thermal jets. In the volume of each of the zones, autonomous circulation occurs.
The level of thermal overlap is determined by the size of the exhaust and supply aeration openings, i.e. air exchange. With a decrease in the area of aeration openings (with a decrease in air exchange), the height of the temperature overlap decreases to the level of the location of the heat source. With an increase in the area of the openings (with an increase in air exchange), the height of the temperature overlap increases and can reach the level of the upper exhaust openings.
For the first time, he observed the phenomenon of temperature overlap and gave this name to E.V. Kudryavtsev (partial ventilation of industrial and public premises. Proceedings of the Academy of Sciences of the USSR. 1948. No. 3). V.V. Baturin also modeled temperature overlap when studying the aerodynamics of an aluminum electrolysis shop
Rice. 34. Temperature overlap scheme
mechanical ventilation
With mechanical ventilation, air exchange is achieved by the pressure difference created by the fans. The main elements of a mechanical ventilation system: a device for sampling outside air (mine), air ducts, fans, gas and dust cleaning installations.
Air intake devices are placed where the air is the cleanest: on the wall of the building, at some distance from the wall or on the roof of the building.
Air ducts, usually cylindrical, are made of steel sheet. Rubber gaskets are placed on the flanges where the duct sections are joined.
Fans are divided into two main types: axial and radial (centrifugal). In axial fans, air moves along the axis of the impeller. The advantages of an axial fan are compactness and the possibility of reversing, i.e. change in airflow direction. In centrifugal fans, the turbine blades throw air to the walls of the fan, from where it enters the duct through a pipe. The advantage of radial fans is higher performance compared to axial fans.
CLEANING GAS EMISSIONS
Existing methods for cleaning industrial air emissions can be classified as follows:
1. Gravitational settling.
2. Dry inertial and centrifugal capture.
3. Wet dust collection.
4. Electrostatic deposition.
5. Filtration.
6. Sonic and ultrasonic coagulation.
As a rule, several methods of dust collection are implemented in treatment plants. Gravitational settling is a relatively uncommon method, as it requires significant production areas for equipment. Inertial settling is based on the tendency of dust particles to maintain their original direction of movement when the flow direction changes. With centrifugal trapping, dust particles tend to move away from the center of rotation. The widely used cyclones operate on this principle. The principle of wet dust collection is used as an addition to the gravitational, inertial and centrifugal cleaning methods. In this case, larger water droplets absorb small and large dust particles, washing them into sediment. Electrostatic deposition is based on the fact that high-voltage electric fields impart a charge to the particles, under the influence of which the particles move to an oppositely charged electrode and settle. The filtration method is based on the separation of gas and the dispersed phase when passing through a porous barrier. Sonic and especially ultrasonic processing of emissions promotes the transfer of energy to moving particles, increases their energy, increases the number of collisions and promotes particle coagulation, which simplifies subsequent dust separation.
The main characteristic of dust cleaning machines is the efficiency of dust collection, i.e. the degree of purification, which is the ratio of the weight of the dust captured by the apparatus to the weight of the dust that has entered it for the same time.
Degree or ratio of purification E is determined by the equation:
| |
where To 1 – initial concentration of dust, mg/m 3 ; To 2 – final concentration of dust, mg/m 3 .
The cleaning coefficient depends on the type of dust cleaning device, the type and dispersion of dust. Particularly important is the fractional composition of dust, since with an increase in fine fractions, the efficiency of the cleaner deteriorates. Therefore, the concept of fractional efficiency was introduced, as the ratio of the weights of the captured and incoming dust of a given fraction. This coefficient is of great importance, since it determines the operation of apparatuses with dusts of various fractional composition.
When comparing the operation of two dust collectors operating under the same conditions, but having different efficiency, for example, 85% and 95%, we can assume that the second one works 10% more efficiently, but if we recalculate for atmospheric pollution, it turns out that the second one is three times more efficient first, because
| |
The characteristics of the dust collector should include not only the cleaning factor, but also the fractional cleaning degree, and it is necessary to know the dust distribution curve related to particle sizes or sedimentation (settling) rates, chemical analysis of dust, humidity, etc.
DUST CLEANING INSTALLATIONS
The simplest apparatus is a dust settling chamber operating on the gravitational principle (Fig. 3.5).
Rice. 3.5. Dust collection chamber Fig. 3.6. Labyrinth dust collector
The disadvantage of these devices is a large occupied area and low cleaning efficiency. In order to reduce the area and increase efficiency, labyrinth type dust settling chambers are used (Fig. 3.6).
Labyrinth-type chambers have baffles that cause the incoming gas to change direction periodically. Therefore, in these chambers, in addition to the gravitational cleaning principle, an inertial one is added.
The main condition for the good operation of the dust settling chamber is the uniform movement of gas through the chamber, since any increase in speed will contribute to the removal of dust particles from the chamber. To prevent this phenomenon, nets, partitions, etc. are installed before entering the chamber.
It should be noted that air ducts with a low speed of movement also work as dust collection chambers, therefore, for better cleaning, they should be placed at an angle. Dust settling chambers are easy to manufacture, require low operating costs, the pressure loss of the air flow due to low speed is negligible, but due to their low efficiency they are used for pre-cleaning.
In inertial dust precipitators, the air flow abruptly changes the direction of movement. Inertial chambers of various designs are shown in fig. 3.7.
a) b)
Rice. 3.7. Inertial precipitator
The efficiency of inertial dust precipitators is low, therefore they, like dust precipitators, are used for preliminary cleaning with subsequent cleaning in some other apparatus.
Centrifugal dust precipitators - cyclones are most widely used in industry.
The advantages of cyclones are high cleaning efficiency and relatively small footprint. The scheme of the cyclone is shown in fig. 3.8.
Dust-laden air enters the top of the cyclone tangentially to the cylinder, and therefore the air flow begins to rotate. dust particles
where F– centrifugal force, kg; G is the weight of a dust particle, kg; U 2 – circumferential speed, m/s; r– radius of rotation, m.
But a decrease in the diameter of the cyclone leads to a decrease in its throughput. Therefore, it is necessary to install several small cyclones in one apparatus.
Such cleaning devices containing several cyclones of small diameter are called multicyclones (Fig. 3.9).
Rice. 3.9. Multicyclone Fig. 3.10. Multicyclone nozzle
On fig. 3.10. the device of a small cyclone is shown, it contains a spiral surface, passing through which the air flow begins to rotate, and a central pipe through which the purified air is removed. The most important condition for the normal operation of the multicyclone is the uniformity of air supply to each cyclone. The efficiency of the multicyclone reaches 95%. The main disadvantage of multicyclones is that they are easily clogged with dust due to the small diameter of the cyclones. Therefore, it is necessary to maintain the temperature regime in order to avoid the formation of condensate and the accumulation of dust. The temperature of the air supplied for cleaning should be 10 0 С lower than the temperature of the cyclone; for this, the cyclone body is covered with thermal insulation or installed in a warm room. Wet dust collection is carried out in scrubbers.
A scrubber is a dust-cleaning apparatus based on the interaction of the cleaned gas with water (Fig. 3.11).
Wet dust collection is also carried out in irrigation towers, various chambers, wet cyclones. When removing dust particles with water, the main task is to obtain maximum contact of dust particles with water droplets.
G.V. Fedorovich, A.L. Petrukhin
Calculation of the thermal state of the body and the determination of comfortable microclimatic working conditions.
You can leave your comments, feedback and opinions about the work of the calculator on our website. In chapter .
Work principles detailed in the guide below.
1.1. Purpose of the calculator:- monitoring the state of the employee's working conditions for compliance with current sanitary rules and regulations, hygienic - establishing the priority of preventive measures and assessing their effectiveness; - drawing up a sanitary and hygienic characteristic of the working conditions of an employee; - analysis of the relationship between changes in the health status of an employee and his working conditions (during periodic medical examinations, a special examination to clarify the diagnosis); - investigating cases of occupational diseases, poisoning and other health problems related to work.
1.2. The calculator can be used:- bodies and institutions of the Federal Service for Supervision of Consumer Rights Protection and Human Welfare in the exercise of control over the implementation of sanitary rules and regulations, hygiene standards in the workplace and social and hygienic monitoring; - organizations accredited to carry out work on the assessment of working conditions; - centers of occupational pathology and occupational medicine, polyclinics and other medical and preventive institutions providing medical care to employees; - employers and employees for information about working conditions in the workplace; - bodies of social and medical insurance.
2.1. Axiomatics. The basic principles of hygienic assessment of microclimate parameters and their connection with the criteria of a person's thermal state are formulated below. The contribution of processes in the body and in the environment to heat exchange at the boundary between them can only be described in terms that are inherent in the heat exchange processes themselves - the temperature of the environment and the surface of the skin, the rate of evaporation of moisture from the surface, etc. Parameters other than those that can be expressed in terms of routine thermodynamic variables should not be used. The reaction of the body can only be a response to the information that it receives from its temperature receptors and only from those places (from the surface of the skin) where these receptors are present. The definitions of heat fluxes and heat balance conditions themselves do not contain estimates of microclimate parameters. Valuation categories are included in the analysis procedure in addition to balance considerations. It should be taken into account that the adaptive mechanisms of the body are very effective and can maintain the heat balance for a sufficiently long time in a wide range of changes in external conditions. Feelings of comfort or discomfort arise as a result of less or more tension in these mechanisms. Quantitative estimates of the degree of intensity of adaptive mechanisms can be based only on those parameters and described in terms that describe the heat transfer processes themselves. Thus, the importance of balance ratios for the heat produced and lost by the body lies in the fact that only the parameters included in these ratios can be used for comparison with subjective assessments of the microclimate.
2.2. Energy consumption: release and loss of energy.Human activity is characterized by several types of released power, :
- The rate of release of total metabolic heat W floor- full energy release due to all sources - chemical processes and muscle activity.
- The rate of release of metabolic heat of the main (background) metabolism in the body w o(≈ 90 W in an adult).
- The rate of release of additional heat associated with the work done W add. It's obvious that W add \u003d W floor - W o
- Mechanical power developed by muscles W fur. The last two values are interconnected by the efficiency of the muscles h = W mech / W extra. Despite some conventionality of introducing this coefficient (it varies from person to person, depends on the type of mechanical work, the general condition of the organism, etc.), it is advisable to use it in calculations, while it can be considered equal to ≈ 0.2. Heat rating W tep, released at a certain level of muscle activity, can be obtained from quite obvious ratios
| Wtep = Wo+ Wadd-Wmech = Wo+(1-h)* Wadd. | (1) |
It is this value that is included in the heat balance equations, while the normative documents use the value W floor.
1. Category Ia include work with an intensity of energy consumption up to 139 W, performed while sitting and accompanied by slight physical stress (a number of professions in precision instrumentation and engineering enterprises, in watchmaking, clothing production, in management, etc.).
2. Category Ib include work with an intensity of energy consumption of 140-174 W, performed while sitting, standing or walking and accompanied by some physical stress (a number of professions in the printing industry, in communications enterprises, controllers, craftsmen in various types of production, etc.).
3. Category IIa include work with an intensity of energy consumption of 175-232 W, associated with constant walking, moving small (up to 1 kg) products or objects in a standing or sitting position and requiring a certain physical exertion (a number of professions in mechanical assembly shops of machine-building enterprises, in spinning and weaving production and etc.).
4. Category IIb include work with an intensity of energy consumption of 233-290 W associated with walking, moving and carrying loads up to 10 kg and accompanied by moderate physical stress (a number of professions in mechanized foundries, rolling, forging, thermal, welding shops of machine-building and metallurgical enterprises, etc. ).
5. Category III include work with an intensity of energy consumption of more than 290 W, associated with constant movement, moving and carrying significant (over 10 kg) weights and requiring great physical effort (a number of professions in blacksmith shops with manual forging, foundries with manual stuffing and pouring of molding boxes for machine-building and metallurgical enterprises, etc.).
2.4. The main channels of heat transfer.The body can regulate (within certain limits) the intensity of heat loss through various channels and “turn on” them in various combinations, depending on the situation: the intensity of work, environmental parameters, the degree of thermal insulation of the body, etc. (for more details, see).
Lung heat transfer. The physiology of respiration is described in detail in many works (see, for example). Heat and moisture exchange during respiration is a complex process in which the inhaled air is moistened and warmed (or cooled) in the upper respiratory tract, and the exhaled air is dried and cooled (or heated). The process is almost cyclical. Heat loss during respiration is due to deviations from cyclicity - the partial pressure of water vapor in the exhaled air is greater than in the inhaled air, this consumes the latent heat of vaporization. When calculating, you should use a multiple linear regression dependence of the rate of moisture loss during respiration on meteorological parameters (air temperature and humidity) , as well as from the physiological characteristics of the body (respiratory rate, tidal volume), obtained in the work. Recalculation to the parameters directly included in the balance equations is carried out in the book. The dependence of heat loss during breathing Wleg on the intensity of muscle activity and air parameters - temperature ta and absolute humidity aa is determined by the formula: / m 3, γp \u003d 12. The proportion of additional energy release due to muscle activity is denoted by ω: ω = Wadd/Wo , and the function γ(ω) = 1 + ω*(0.5 + ω) interpolates an increase in the rate of pulmonary ventilation with an increase in muscle activity. The value of Wleg should be subtracted from the thermal power Wtherm when calculating heat losses from the body surface. Due to the heat exchange at the border of the skin - the inner surface of the clothing, the power Wpol - Wleg should be removed. Recalculating the power per unit of body surface, we obtain the heat flux density Here S ≈ 2 m 2 - the surface area of the body of an adult. The flow with density Jko should be provided by conductive skin-clothing heat exchange. Conductive heat exchange skin-clothing. The flow Jco of heat through clothing is determined by the temperature difference between the skin tк and the surface of clothing tp and the thermal resistance of clothing Iclo: , where ι = 0.155 °C * m 2 / W is the coefficient for converting conventional units Clo into the actual thermal resistance of clothing. Heat loss from the surface of clothing. Conductive and radiative heat exchange channels operate on the clothing surface. Conductive heat exchange with the environment is proportional to the temperature difference between the surface of clothing and air: here the value of air velocity Va is substituted in units of m/s. Another channel of heat exchange on the surface of clothing is heat exchange due to radiation and absorption of radiant energy. If the density of the radiant energy flux incident on the surface is presented as radiation), then the heat flux from the surface of the clothing will have the form
| Jrad \u003d εpo * σ * (Tp 4 - Trad 4) | (8) |
| Wpot= Kk*S*(1 - RH*exp[ (tv - tk)/ to ]) | (9) |
2.5. Physiological characteristics of the thermal state of the body.
Generalized data on changes in physiological parameters during muscular activity, given in the book, are used. To ensure the normal thermal state of the body, certain relationships must be observed between the intensity of muscle activity (determined, for example, by the magnitude of the mechanical power Wmech or by the value of the total energy release Wpol, unambiguously associated with it by relation (1) and such physiological reactions of the body as the magnitude of moisture loss and the weighted average skin temperature (STC). There are two modes of operation of thermoregulation systems. One of them is “natural” for the body, while the person feels comfortable. The external conditions that ensure such a state are defined as optimal. To ensure a normal temperature regime under non-optimal external conditions, the regulatory systems of the body begin to work with some tension of their capabilities. However, if the external conditions are not too different from the optimum, the voltage of the thermostatic systems is sufficient to maintain the heat balance. The concretization of this qualitative description of the thermal state of the body is given below. Table 1.
Indicators of the thermal state of a person, which are the basis for the development of requirements for the parameters of the optimal microclimate.
| Nature of work | Energy consumption Wpol, W | Moisture loss, Q, g/h | SVTK, °С |
| Light, category Ia | up to 139 | 40-60 | 32,2 - 34,4 |
| Light, category I b | 140-174 | 61-100 | 32,0 - 34,1 |
| Medium, category IIa | 175-232 | 80-150 | 31,2 - 33,0 |
| Medium, category IIb | 233-290 | 100-190 | 30,1 - 32,8 |
| Heavy, category III | 291 - 340 | 120-250 | 29,1 - 31,0 |
The scatter in the values of moisture loss and SVTK is due to the fact that they are related to the range of energy consumed.
Fig.1. The rate of moisture loss corresponding to the comfortable state of the body (middle line) and the allowable voltage of thermoregulation systems (extreme lines).
In Fig.1, the data of Table 1 on the moisture loss of the body are shown in graphical form. Inside the rectangles, according to the data of Table 1, the indicators of the thermal state of a person correspond to comfortable ones. The limits of allowable stresses of the thermoregulation system are determined by the upper and lower straight lines on the plane (W,Q). Outside the boundaries defined by these lines, the thermoregulation systems are overstressed and overheating or hypothermia of the body begins. For calculations, it is possible to use the interpolation of the dependence of the moisture loss Q on energy consumption W of the form Recalculation to the energy spent on sweat evaporation gives a similar formula, where the coefficient K = r * k is 0.26 for the lower limit of permissible values, 0.39 for optimal and 0.61 for the upper limit of permissible values. Similar graphs for the weighted average skin temperature tk depending on the energy consumption Wpol are shown in Fig.2.
Fig.2. The weighted average skin temperature corresponding to the comfortable state of the body (middle line) and the allowable stress of thermoregulation systems (extreme lines).
It can be seen that, in contrast to the rate of moisture loss, which increases with energy consumption, the skin temperature decreases with increasing Wpol. This is quite expected, because. the greater the production of heat, the more intensive should be its removal from the internal parts of the organism to the surface. For this (at a constant temperature of the internal organs) a decrease in skin temperature is required. For calculations, you can use the interpolation of the dependence of the value of the SVTC on energy consumption Wpol of the form , where the temperature scale t1 is 33.1 °C for the lower limit of permissible values, 35.4 °C for optimal and 36.5 °C for the upper limit of permissible values. For power scale W1, the corresponding values are 2739W, 2185W and 3094W, respectively. If the regulatory capabilities of the heat balance maintenance systems are not enough, the enthalpy (heat content) of the body begins to change. This leads to discomfort, and with large variations in enthalpy - to professionally caused health disorders. For a heating microclimate, the relationship between the excess of enthalpy and the class of working conditions, as well as with a descriptive assessment of the risk of overheating of the body, is presented in Table 2. Table 2.
Harmful effects of excess body enthalpy on the health of workers.
Similarly, the harmful effects of microclimatic conditions increase when the body is overcooled. For a cooling microclimate, the relationship between the enthalpy deficit and the class of working conditions is presented in Table 3. Table 3
Harmful effects of body enthalpy deficiency on the health of workers
Qualitative risk assessment coincides with the data in Table 2 for the corresponding classes of working conditions. The data given in tables 1 - 3, together with the above-described algorithms for calculating the body's heat exchange with the external environment, are the basis for making judgments about working conditions based on the results of measurements of real microclimatic parameters of the production environment.
3. Controlled indicators of the microclimate.
From the ratios given in paragraph 2.4 above, it follows that when studying the thermal state of a person, the following microclimate parameters should be measured:
air temperature Ta;
relative air humidity RH;
air velocity Va;
intensity of thermal irradiation IR;
The relative role of the listed parameters is not the same. The air temperature enters directly into the heat balance equations. The characteristic scale of temperature variations, judging by the data given in Table 1, is several tenths of a degree. This corresponds to a relative uncertainty of ≈ 10 -3 (0.1%) and sets the allowable error of the measuring equipment. Relative humidity RH determines the amount of lung heat loss. This value is a small fraction (not more than 25%) of the heat transfer through the conductive heat loss channel, according to formula (2), the relative value of the term proportional to air humidity is not more than 20% of the value of the remaining terms. These circumstances determine the low requirements for measuring relative humidity. An error of 5 - 10% is quite acceptable for measuring relative humidity. The speed of air movement directly determines the coefficient of heat transfer from the surface of clothing according to formula (7). Since the uncertainty of the temperature difference between the air and the surface of clothing can be a few percent, then, accordingly, the requirements of ≈ 5-10% for the relative error in measuring the speed provide quite sufficient measurement rigor. Estimation of the intensity of thermal exposure introduces the greatest uncertainty into the calculations of the influence of the microclimate on the thermal state of the worker's body. The most reliable way to measure this value is to use a balloon thermometer.
3.1. Measurement of the effective value of thermal exposure.The heat flux due to infrared radiation is a vector quantity. Accordingly, sensors used in measuring instruments can be either directional or isotropic. Almost all devices used in the domestic practice of sanitary and hygienic control are IR radiometers with a limited viewing angle. These devices with directional sensors can be used to measure thermal radiation fluxes from sources with small angular dimensions that fall completely within the field of view of the radiometer. In the case of a large source, or if there are several sources and irradiation occurs from several directions, processing the measurement results is a non-trivial task that does not always have a correct solution. The problem is practically unsolvable for non-stationary (for example, moving) sources. Ball thermometer (Vernon sphere) is an instrument with isotropic sensitivity, most suitable for measuring integral (comprehensive) thermal exposure. The corresponding algorithm for converting the results of temperature measurements into integral thermal exposure is described in. Such a recalculation is based on the heat flux balance equation for the sphere. This value should be used when assessing the thermal state of the body. Relation (16) determines the thermal effect of IR radiation through the well-measured temperatures of the sphere Tg and air Ta, however, it also includes the temperature of the surface of clothing Tc, the measurement of which is much more difficult: it must be measured in several places of clothing with subsequent averaging of the results. Losing somewhat in accuracy, we can replace the temperature Tc in (16) with the air temperature Ta. This leads to a significant simplification of the procedure for monitoring microclimate parameters. The result of such a replacement has the meaning of an effective flow of thermal radiation, it is he who is subject to hygienic rationing.
| ΔJ \u003d ε * σ * (T g 4 -T a 4) + h c * (T g -T a) | (17) |
Thermal irradiation fluxes corresponding to the difference Δt of air temperatures ta and the ball thermometer
|
ta |
10 | 14 | 18 | 22 | 26 | 30 |
| 2 | 24,76 | 25,21 | 25,66 | 26,13 | 26,62 | 27,11 |
| 4 | 49,74 | 50,64 | 51,56 | 52,51 | 53,48 | 54,48 |
| 6 | 74,95 | 76,30 | 77,69 | 79,12 | 80,59 | 82,10 |
| 8 | 100,38 | 102,2 | 104,07 | 105,99 | 107,96 | 109,99 |
| 10 | 126,04 | 128,33 | 130,68 | 133,1 | 135,58 | 138,13 |
| 12 | 151,94 | 154,7 | 157,55 | 160,47 | 163,46 | 166,54 |
| 14 | 178,07 | 181,32 | 184,66 | 188,09 | 191,61 | 195,23 |
| 16 | 204,44 | 208,18 | 212,03 | 215,97 | 220,02 | 224,18 |
| 18 | 231,06 | 235,3 | 239,65 | 244,12 | 248,71 | 253,42 |
| 20 | 257,92 | 262,66 | 267,53 | 272,53 | 277,66 | 282,93 |
| ΔJ \u003d * (T g -T a) | (18) |
4. Selection of clothing as a means of individual protection against the adverse effects of meteorological parameters.
Reasonable recommendations on the choice of clothing that ensures comfortable work in real-life production conditions are an important point in sanitary and hygienic research during automated workplaces and production control. By choosing the right clothing, you can significantly improve working conditions and reduce occupational risks without changing the working environment. For this, however, the recommendations must be convincingly substantiated by the results of calculations of the body's heat exchange with the environment.
The materials of items 2-3 indicate that the two main channels of heat exchange with the environment - radiation and conductive - determine the thermal state of the body (see, for example, expression (17) for the heating rate). To determine what PPE should protect against, it is necessary to evaluate the relative role of the mentioned heat transfer channels.
Estimates can be made using relation (16), in which the difference in the fourth powers of temperature is estimated by the difference in the temperatures themselves (see above the transition from (17) to (18)). In other words, when the radiation temperature exceeds normal room temperature, one should protect oneself from excessive thermal exposure, and at lower radiation temperatures - from overheating or hypothermia of the body due to conductive heat transfer.
4.2. Overalls from heat-reflecting fabric for "hot shops".
Thermal protective clothing provides protection for workers working in hot shops from sparks, scale, splashes of molten metal, radiant heat. The range of such overalls is represented by suits, aprons, mittens, overalls. Linen and cotton fabrics with flame retardant impregnations are used for the production of overalls. Most of these fabrics have a sufficiently dense and smooth surface, from which sparks and splashes of molten metal easily roll off. In order to reflect radiant heat, non-textile materials with an aluminum coating are used.
Suits for work in hot shops are made according to GOST 9402-70 (male) and according to GOST 9401-70 (female). The design of these suits can be built on the basis of the design basis of the second and third variants of the first group of workwear products. This type of clothing is intended for workers of various professions (steelmaker, steelmaker's assistant, crane operator, roller operator, boilermaker, pourer, blacksmith, etc.). The suit is used when working in open-hearth, steel-smelting, rolling, foundry-boiler and blacksmith shops, in which the temperature at the workplace reaches + 50 ° C, and the intensity of exposure to radiant heat is up to 18-20 cal / (cm2min).
Reasonable recommendations on the choice of clothing that ensures comfortable work in real-life production conditions are an important point in sanitary and hygienic research during automated workplaces and production control.
By choosing the right clothing, you can significantly improve working conditions and reduce occupational risks without changing the working environment. For this, however, the recommendations must be convincingly substantiated by the results of calculations of the body's heat exchange with the environment. Depending on the goals of such calculations (requirements for microclimate parameters, restrictions on energy consumption, calculation of thermal resistance of clothing, etc.), an algorithm and sequence of analysis of individual heat exchange channels should be selected. The use of a ball thermometer greatly simplifies and refines the calculation of the thermal resistance of clothing that provides individual protection from the adverse effects of microclimatic conditions.
If initially set by the total energy consumption Wpol, for heat transfer calculations, the mechanical power Wmech, heat loss for sweat evaporation Wpot, and heat loss during breathing Wleg should be subtracted from them. The remaining power Wh = Wpol - Wpot - Wleg must be dissipated through clothing. The corresponding heat flux J is given by the formulas:
| J \u003d W h ⁄ S \u003d (t s - t c) ⁄ Iclo | (21) |
Studies on the physiology of thermoregulation show that for each level of energy consumption there is a physiologically determined optimal skin temperature ts, so that if we determine the temperature of the surface of clothing tc, then from equation (16) we can determine the value of thermal resistance of clothing Iclo, which provides optimal working conditions with given total energy costs Wpol. To determine tc, the heat transfer equation is solved taking into account the conductive and radiative heat transfer channels on the clothing surface: by solving which we determine the temperature Tc of the clothing surface, after which Iclo is determined from (21).
The heat transfer coefficient hg from the surface of the Vernon sphere is determined both by the design of the sphere (its diameter) and the meteorological parameters (air velocity, temperature, etc.). It is possible to choose a sphere for which this coefficient will be equal to the heat transfer coefficient hcc of the clothing surface. In this case, the air temperature Ta is not included in the equation for determining the temperature of the clothing surface Tc - the readings of a ball thermometer are sufficient to determine Tc. This greatly simplifies the calculation of the thermal resistance of clothing that provides comfortable working conditions.
In any case, the use of clothing with correctly calculated thermal resistance is an example of the effective selection of personal protective equipment against the adverse effects of microclimatic conditions. An example of specific calculations demonstrating how much working conditions can be improved in this way is given in the work. It is quite realistic to lower the hazard class by 2-3 points.
5. Algorithms for processing measurement results.
5.1.
The equations given in paragraphs 2-4 can be used to solve various problems related to the optimization of heat exchange between the worker's body and the environment. The results of such calculations lead to a "blurring" of the boundary between the heating and cooling microclimate. It can be shown that, depending on the amount of energy consumption, the quality of clothing and other factors, working in an environment with the same microclimatic parameters can in some cases lead to overheating of the body, and in others to hypothermia. This circumstance is illustrated by the data table 5.
Table 5
Enthalpy build-up rate dH ⁄ dt (kJ ⁄ kg ⁄ hour) when performing work with total energy consumption Wpol (W) performed in clothes with thermal resistance Clo (c.u.)
| Clo Wpol |
0,1 | 0,4 | 0,7 | 1 | 1,3 | 1,6 | 1,9 | 2,2 | 2,5 |
| 100 | -4,39 | -2,03 | -0,62 | 0,33 | 1,01 | 1,52 | 1,92 | 2,23 | 2,49 |
| 120 | -3,67 | -1,27 | 0,17 | 1,13 | 1,82 | 2,34 | 2,74 | 3,06 | 3,33 |
| 140 | -2,88 | -0,44 | 1,02 | 2,00 | 2,70 | 3,23 | 3,64 | 3,97 | 4,24 |
| 160 | -2,00 | 0,48 | 1,97 | 2,97 | 3,68 | 4,22 | 4,64 | 4,97 | 5,25 |
| 180 | -0,98 | 1,54 | 3,05 | 4,06 | 4,79 | 5,33 | 5,76 | 6,10 | 6,38 |
| 200 | 0,20 | 2,75 | 4,29 | 5,32 | 6,06 | 6,61 | 7,05 | 7,39 | 7,68 |
| 220 | 1,58 | 4,18 | 5,74 | 6,79 | 7,54 | 8,10 | 8,54 | 8,89 | 9,18 |
| 240 | 3,23 | 5,86 | 7,45 | 8,51 | 9,28 | 9,85 | 10,30 | 10,65 | 10,95 |
| 260 | 5,19 | 7,87 | 9,48 | 10,56 | 11,33 | 11,92 | 12,37 | 12,73 | 13,03 |
| 280 | 7,54 | 10,26 | 11,90 | 12,99 | 13,78 | 14,37 | 14,83 | 15,20 | 15,50 |
| 300 | 10,35 | 13,11 | 14,77 | 15,88 | 16,68 | 17,28 | 17,75 | 18,12 | 18,43 |
When constructing this table, the following environmental parameters were taken: air temperature ta = 20°C, ball thermometer temperature tg = 23 oC, relative air humidity RH = 50%, air velocity Va = 0.25 m/s, coefficient of absorption of thermal radiation by the surface clothes ε = 0.3, worker weight 75 kg.
It can be seen that when performing even fairly hard work (with energy consumption up to 200 W) in light clothing, the body can become supercooled (dH ⁄ dt< 0), т.е. этот микроклимат будет охлаждающим, но при выполнении работы в одежде с большим термосопротивлением (Clo >1) overheating of the body can be observed (dH ⁄ dt > 0), i.e. the same microclimate should be recognized as heating.
5.2.
The calculation of the heat balance can be used to select clothing that provides comfortable, or at least acceptable working conditions. As an example of the results of such a calculation, the data contained in Table 6 can be cited.
In calculations, it was assumed that thermal irradiation leads to the fact that the temperature of the balloon thermometer is 2.5°C higher than the air temperature. The relative humidity of the air was assumed to be 35%, the air velocity Va = 0.25 m/s, the degree of non-blackness of the clothing surface in the IR region of the spectrum ε ≈ 0.2.
Table 6
Thermal resistance (Clo) of clothing that provides optimal and acceptable working conditions with a given energy consumption W (W) at a given air temperature ta (°C)
| 16 | 18 | 20 | 22 | 24 | 26 | |
| 100 | 2,06 | 1,7 | 1,36 | 1,05 | 0,76 | 0,49 |
| 1,66 | 1,31 | 0,99 | 0,69 | 0,41 | 0,16 | |
| 1,3 | 0,97 | 0,66 | 0,37 | 0,11 | <0 | |
| 120 | 1,7 | 1,39 | 1,1 | 0,83 | 0,58 | 0,34 |
| 1,31 | 1,01 | 0,74 | 0,48 | 0,24 | 0,02 | |
| 1 | 0,71 | 0,45 | 0,2 | <0 | <0 | |
| 140 | 1,41 | 1,13 | 0,88 | 0,64 | 0,42 | 0,21 |
| 1,04 | 0,78 | 0,53 | 0,31 | 0,1 | <0 | |
| 0,76 | 0,5 | 0,27 | 0,06 | <0 | <0 | |
| 160 | 1,18 | 0,92 | 0,69 | 0,48 | 0,28 | 0,1 |
| 0,82 | 0,58 | 0,36 | 0,16; | <0 | <0 | |
| 0,56 | 0,34 | 0,13 | <0 | <0 | <0 | |
| 180 | 0,97 | 0,74 | 0,53 | 0,34 | 0,16 | <0 |
| 0,63 | 0,41 | 0,22 | 0,04 | <0 | <0 | |
| 0,4 | 0,19 | 0,01 | <0 | <0 | <0 | |
| 200 | 0,79 | 0,58 | 0,38 | 0,21 | 0,05 | <0 |
| 0,46 | 0,26 | 0,09 | <0 | <0 | <0 | |
| 0,25 | 0,07 | <0 | <0 | <0 | <0 | |
| 220 | 0,62 | 0,43 | 0,25 | 0,1 | <0 | <0 |
| 0,31 | 0,13 | <0 | <0 | <0 | <0 | |
| 0,12 | <0 | <0 | <0 | <0 | <0 | |
| 240 | 0.46 | 0.29 | 0.13 | <0 | <0 | <0 |
| 0.17 | 0,01 | <0 | <0 | <0 | <0 | |
| 0 | <0 | <0 | <0 | <0 | <0 | |
| 260 | 0.32 | 0.16 | <0 | <0 | <0 | <0 |
| 0,04 | <0 | <0 | <0 | <0 | <0 | |
| <0 | <0 | <0 | <0 | <0 | <0 | |
| 280 | 0.18 | <0 | <0 | <0 | <0 | <0 |
| <0 | <0 | <0 | <0 | <0 | <0 | |
| <0 | <0 | <0 | <0 | <0 | <0 |
In table 6, each combination of parameters (W, ta) corresponds to three values of clothing thermal resistance. The average value corresponds to the optimal state of the body: the optimal skin temperature and optimal perspiration (see paragraphs 2-4 above). The extreme values of Clo correspond to the allowable stress of the thermoregulatory systems of the body: the upper one corresponds to the minimum skin temperatures and perspiration, the lower one corresponds to the maximum values of these parameters.
The way to interpret these results can be illustrated by the example of working with 100 W at 16°C (upper left triad in the table). Working conditions in clothes with thermal resistance from 2.06 Clo to 1.3 Clo are acceptable, and if Clo is close to 1.7, the conditions will be optimal. Negative RTDs are not possible for normal clothing, so the corresponding boxes in Table 5 should be interpreted as "narrowing" the ranges of possible clothing RTDs. For example, when working with an energy consumption of 100 W at a temperature of 26 ° C (upper right triad in the table), the permissible conditions are limited by clothing resistances from 0.49 to 0 (no clothing), and clothing with Clo = 0.16 creates optimal working conditions.
With an increase in energy consumption, the permissible thermal resistance of clothing decreases, for example, at W = 200 W and ta = 16 ° C, thermal resistance in the range from 0.25 to 0.79 Clo (optimally 0.46 Clo) is acceptable. At an air temperature of 26 ° C, it is impossible to choose clothes to create acceptable working conditions. Such a microclimate can be called absolutely heating for work with an energy consumption of 200 watts. At ta = 22°C, clothes with thermal resistance up to ≈ 0.2 Clo provide acceptable working conditions, but it is impossible to ensure optimal conditions only by selecting clothing thermal resistance.
5.3.
Operation at low air temperatures can be optimized by using infrared heaters. The selection of the required values of thermal exposure can also be made on the basis of the balance ratios of clause 3.4. The results of the corresponding calculations are shown in Table 7. The calculations assumed: air temperature 12.5°C; relative air humidity RH = 35%; air velocity Va = 0.25 m/s; the degree of non-blackness of the clothing surface in the IR region of the spectrum ε ≈ 0.4.
Data structures in the cells of Table 6 and Table 5. are similar.
The presented data indicate that at low energy consumption (for example, at W = 100 W), the thermal irradiation of a lightly dressed person (Clo ≈ 0.4) should be at the level of 320 W/m2, however, if the thermal resistance of clothing is sufficiently high (Clo ≈ 2.4), additional irradiation is practically not required. For work with high energy consumption (for example, at W = 200 W), additional heating (at the level of 170 W/m2) is required only for lightly dressed workers, but even with clothing thermal resistance Clo ≈ 1, the absence of additional thermal exposure will be optimal. The negative results of calculations of thermal irradiation at high energy consumption indicate the need for additional cooling. For example, if W = 300 W, only light clothing (with Clo< 0,5) может обеспечить допустимые (но не оптимальные) условия труда. Для одежды с большим термосопротивлением работа с W = 300 Вт будет приводить к недопустимому перегреву организма. Единственная возможная защита от перегрева в этом случае - ограничение времени работы, с тем, чтобы дополнительная энтальпия не превышала допустимых величин (см. выше п.2.5).
Table 7
| The intensity of thermal irradiation (W / m 2), necessary to maintain thermal balance when doing work with energy costs W (W) in clothes with thermal resistance Сlo | ||||||
|---|---|---|---|---|---|---|
| 0,4 | 0,8 | 1,2 | 1,6 | 2,0 | 2,4 | |
| W (W) | ||||||
| 100 | 380,33 | 318,97 | 258,11 | 197,76 | 137,89 | 78,51 |
| 319,01 | 257,93 | 197,35 | 137,27 | 77,67 | 18,54 | |
| 263,54 | 202,78 | 142,52 | 82,75 | 23,45 | < 0 | |
| 120 | 360,7 | 289,19 | 218,37 | 148,22 | 78,73 | 9,88 |
| 292,07 | 220,9 | 150,42 | 80,6 | 11,43 | < 0 | |
| 235,19 | 164,38 | 94,24 | 24,77 | < 0 | < 0 | |
| 140 | 340,74 | 259,01 | 178,19 | 98,23 | 19,13 | < 0 |
| 264,8 | 183,49 | 103,06 | 23,5 | < 0 | < 0 | |
| 206,5 | 125,58 | 45,53 | < 0 | < 0 | < 0 | |
| 160 | 319,54< 0 | 227,23 | 136,05 | 45,99 | < 0 | < 0 |
| 236,3 | 144,48 | 53,78 | < 0 | < 0 | < 0 | |
| 176,58 | 85,17 | < 0 | < 0 | < 0 | < 0 | |
| 180 | 295,92 | 192,25 | 90,01 | < 0 | < 0 | < 0 |
| 205,4 | 102,3 | 0,61 | < 0 | < 0 | < 0 | |
| 144,25 | 41,59 | < 0 | < 0 | < 0 | < 0 | |
| 200 | 268,39 | 152,11 | < 0 | < 0 | < 0 | < 0 |
| 170,6 | 54,98 | < 0 | < 0 | < 0 | < 0 | |
| 108,02 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| 220 | 235,2 | 104,48 | < 0 | < 0 | < 0 | < 0 |
| 130,16 | 0,22 | < 0 | < 0 | < 0 | < 0 | |
| 66,15 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| 240 | 194,31 | < 0 | < 0 | < 0 | < 0 | < 0 |
| 82,05 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| 16,6 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| 260 | 143,39 | < 0 | < 0 | < 0 | < 0 | < 0 |
| 23,95 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| < 0 | <0 | < 0 | < 0 | < 0 | < 0 | |
| 280 | 79,87 | < 0 | < 0 | < 0 | < 0 | < 0 |
| < 0 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| < 0 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| 300 | 0,89 | < 0 | < 0 | < 0 | < 0 | < 0 |
| < 0 | < 0 | < 0 | < 0 | < 0 | < 0 | |
| < 0 | < 0 | < 0 | < 0 | < 0 | < 0 | |
6. Literature
1. Timofeeva E.I., Fedorovich G.V. Ecological monitoring of microclimate parameters. M., NTM-Protection, 2007, 212 p.
2. Ivanov K.P. etc. Physiology of thermoregulation. L, Nauka, 1984, 470 p.
3. Krichagin V.I. Principles of an objective assessment of the thermal state of the body. - In the book. Aviation and space medicine (under the editorship of Parin V.V.).-M. 1963. p. 310-314.
4. Breslav I.S., Isaev G.G. (ed). Physiology of respiration - St. Petersburg, Nauka, 1994, 680 p.
5. Ergonomics of the thermal environment - Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria” ISO 7730:2005(E).
6. Hirs D., Pound G., Evaporation and Condensation, (translated from English), IIL, M., 1966.
7. Fedorovich G.V. Microclimate parameters providing comfortable working conditions. // Biot - 2010 - №1 - p.75
