Values ​​of constancy of meteorological conditions indoors. Study of meteorological conditions of industrial premises - abstract

Plan

Lecture No. 4 Standardization of indoor air parameters

4.1. Ventilation requirements

The production process is accompanied by the release of large amounts of heat, moisture, dust, gases and vapors into the air of the working premises. As a result, a change occurs in its chemical composition and physical state, which adversely affects the well-being and health of a person and worsens working conditions. To maintain normal indoor air parameters that meet sanitary, hygienic and technological requirements, ventilation is installed.

Ventilation refers to a set of measures and devices that ensure the calculated air exchange in the premises of residential, public and industrial buildings.

Sanitary and hygienic purpose Ventilation consists of maintaining indoor air conditions that meet the requirements of sanitary design standards for industrial enterprises and building codes and regulations by assimilating excess heat and moisture, as well as removing harmful gases, vapors and dust.

For some industrial premises (for example, textile, radio engineering, food industry, etc.) ventilation devices must maintain temperature parameters; relative humidity, mobility and air purity at a certain level resulting from the characteristics of the technological process; Thus, simultaneously with sanitary and hygienic requirements, technological requirements for ventilation must also be met.

Technological requirements– ensuring cleanliness, temperature, humidity and speed of air movement in the room, resulting from the characteristics of the technological process in industrial buildings and the purpose of the room in public buildings.

In addition, ventilation devices must meet the following requirements: a) the area for placing ventilation equipment and ducts must be minimal; the placement of ventilation ducts, devices for air distribution and intake must be combined with the architectural appearance of the premises and not deteriorate the interiors; b) in industrial buildings, ventilation devices should not interfere with the production process; c) good vibration and sound insulation of ventilation equipment from building structures must be ensured; d) the operational characteristics of ventilation systems are extremely important, which, as a rule, should be taken into account when designing - the ability to reliably adjust and regulate the operation of individual elements of ventilation system devices in order to ensure or the required change in air flow rates in the supply and exhaust openings; regulation of the operation of heaters, fans and other devices; ease of maintenance and repair; e) minimum cost of equipment and construction and installation work, maximum possible savings in electricity and fuel during the operation of ventilation units, the possibility of easy and reliable regulation or switching from one operating mode to another when the release of calculated hazards changes.

It follows from the above that in order to ensure normal indoor air parameters, issues of ventilation, technology and architectural and planning solutions for the building must be resolved together.

4.2. Main tasks of ventilation systems

Human health and performance are largely determined by the microclimate and indoor air conditions.

Maintaining the composition and condition of air in a room that satisfies hygienic and technological requirements is the main internal task of ventilation. The external task of ventilation is aimed at protecting the air basin from pollution.

The solution to the internal problem is carried out:

Removal of harmful emissions from the place of their formation (use of exhaust ventilation);

By diluting released harmful substances to certain concentrations with outside air;

Heating, cooling, humidification and purification of outdoor air entering the room;

Distribution of air across separate zones of the room.

To solve an external problem it is necessary:

Clean the air released into the atmosphere from contaminants;

Remove ventilation emissions contaminated with harmful substances to places outside the building where they would be most diluted;

Use full or partial air recirculation in rooms.

Based on the above, ventilation can be defined as a set of measures and devices aimed at maintaining indoor conditions required by regulatory documents and protecting the atmosphere from pollution. The carrier of harmfulness, with the exception of radiant heat, is air. Therefore, ventilation can also be called the science of organizing air exchange in a room.

Modern industrial development is characterized by constant improvement, and therefore changes in technological processes. This significantly affects the efficiency of ventilation devices. In the conditions of rapidly changing technology, placing various production facilities in one room over a huge area without dividing walls, it is necessary to change the principle of determining air exchange, to move away from traditional solutions for air distribution and placement of ventilation equipment.

The air exchange of premises, which now reaches tens of millions of cubic meters per hour for individual workshops, should be determined not by any specific technology, but by the nature of production and calculated per unit of production area, equipment, products, number of people, with mandatory consideration of development prospects. In this regard, it seems relevant to create a room microclimate with air speed varying in time and space, which can be achieved, in particular, by using ventilation with quantitative regulation of air exchange.

Due to the tight fuel balance of the country, it is necessary to reduce energy consumption by ventilation systems as much as possible. However, saving energy should not be an end in itself: the feasibility of energy-saving measures must be economically justified.

4.3. Basic concepts used in the study of ventilation

When studying ventilation, you need to know the following definitions of basic concepts.

Harmful production factor(including dust and gas contamination of the air in the working area, increased or decreased temperature of the surface of equipment, materials and air in the working area) is a production factor, the impact of which on a worker leads to illness.

Imbalance– the difference in air flow rates supplied to the room and removed from it by ventilation systems with artificial impulse and air heating.

Breathing zone– space within a radius of up to 50 cm from the worker’s face.

Local suction– a device for removing gases, vapors, aerosols and dust from the places of their formation.

Microclimate of production premises– the climate of the internal environment of these premises, which is determined by the combinations of temperature, humidity and air speed acting on the human body, as well as the temperature of surrounding surfaces.

Service area– volume of the room, air parameters in which are regulated by heating, ventilation and air conditioning systems. The service area in residential and public buildings and in auxiliary premises is considered to be a space up to 2 m above the floor level, and in rooms where people are mainly in a sitting position (for example, the halls of theaters, restaurants, canteens, educational institutions), the height up to 1.5 m above floor level.

Transitional conditions between the warm and cold periods of the year - meteorological conditions characterized by the following design parameters of outside air: for heating and ventilation systems - temperature 8 o C and specific enthalpy 22.5 kJ/kg (for ventilation systems it is allowed to take parameters whose values ​​are determined by the limit of use of unheated outside air for inflow); for air conditioning systems - a parameter at which the air conditioner does not consume heat and cold.

Work zone– a space 2 m high above the floor and platform level, in which there are places of permanent or temporary residence of workers.

Workplace– a place of permanent or temporary stay of workers in the process of labor activity.

A permanent workplace is considered to be one in which the worker spends the majority (more than 50% or more than 2 hours continuously) of his working time. If processes are serviced at various points in the work area, then the entire work area is considered a permanent workplace.

A workplace in which the worker spends less than 50% or less than 2 hours of his working time is considered non-permanent.

Heat and humidity ratio– the ratio of the change in the specific enthalpy of the air in the room to the change in moisture content or the ratio of the sum of sensible and latent heat to the amount of moisture released, expressed in kJ/kg.

Warm period of the year– a period of the year characterized by an average daily outside air temperature higher than for transitional conditions of the year.

Cold season– a period of the year characterized by an average daily outside air temperature lower than for transitional conditions of the year.

Sheer warmth– heat entering the workroom from equipment, heating devices, heated materials, people and other heat sources, as a result of insolation and the impact on the air temperature in this room.

4.4. Hygienic regulation of microclimate

Engineering systems, which include ventilation systems, must provide optimal or permissible levels of both physical and chemical environmental factors.

The combination of meteorological factors and the temperature of surrounding surfaces determines room microclimate .

The microclimate of the premises is characterized by the temperature of the internal air t in, the radiation temperature of the internal surfaces of the fences t R, the relative humidity of the air j in. The combination of these parameters, which ensures the best well-being and highest performance of a person, is called comfortable conditions . It is especially important to maintain certain temperature conditions in the room. Relative humidity and air speed usually have slight fluctuations.

The calculated parameters of the air environment in a room when designing ventilation are the air parameters that determine comfortable conditions and satisfy the requirements of the technological process. Distinguish optimal And acceptable meteorological conditions indoors. Optimal parameters represent a combination of air environment, the systematic influence of which on a person ensures the preservation of the normal and functional state of the body without straining thermoregulation reactions, creating a feeling of thermal comfort, which contributes to a high level of performance. Valid parameters with prolonged and systematic exposure to a person, they can cause transient and quickly normalizing changes in the functional and thermal state of the body and the tension of thermoregulation reactions, which do not go beyond the physiological capabilities of a person.

The required meteorological conditions in premises (internal conditions) must be ensured in the working (serviced) area of ​​the premises or at permanent workplaces.

Introduction

1.2 Optimal microclimate conditions

1.3 Acceptable microclimate conditions

1.4 Determination of the thermal load index of the environment (THC index)

1.5 Regulation of work time when the air temperature in the workplace is above or below permissible values

2. Technological processes and equipment that cause unfavorable microclimatic parameters in the workplace

3. Prevention of overheating and hypothermia

4 Monitoring microclimate parameters, requirements for its organization and measurement methods

4.1 Control of microclimate parameters

4.2 Requirements for control organization and measurement methods

5. Measures to normalize the air condition of industrial premises

6. Design of systems for protecting the body of workers from the effects of adverse production factors

6.1 Architectural and planning measures

6.2 Engineering and technological measures

6.2.1 Ventilation systems

6.2.2 Air conditioning

6.2.3 Heating of industrial premises

Conclusion

Bibliography

Application

Introduction

The state of human health and performance largely depend on the microclimate in the workplace. Without the ability to effectively influence the climate-forming processes occurring in the atmosphere, people have high-quality systems for controlling air environmental factors inside industrial premises.

The microclimate of industrial premises is the climate of the internal environment of these premises, which is determined by the combination of temperature, relative humidity and air speed acting on the human body, as well as the temperature of surrounding surfaces (GOST 12.1.005 “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").

Factors influencing the microclimate can be divided into two groups: unregulated (a complex of climate-forming factors in a given area) and regulated (features and quality of construction of buildings and structures, intensity of thermal radiation from heating devices, air exchange rate, number of people and animals in the room, etc. ). To maintain the air parameters of work areas within hygienic standards, the factors of the second group are of decisive importance.

Numerous studies by hygienists and occupational physiologists have established that the human body is significantly influenced by sanitary and hygienic factors of the working environment: meteorological conditions, noise, vibration, lighting. Some of them have an adverse effect on the worker, which reduces performance, worsens health and sometimes leads to occupational diseases. Therefore, it is necessary to know not only the cause of these factors, but also to have an idea of ​​ways to reduce their negative impact on the body of workers. Particular attention in this work is paid to the study of microclimate parameters in the workplace, their impact on the body of workers, as well as measures to reduce their negative impact.

The relevance of the topic is that the microclimate plays an extremely important role on the state and well-being of a person, and the requirements for heating, ventilation and air conditioning directly affect the health and productivity of a person.

The purpose of this work was to study the regulatory and technical literature regulating the rules and regulations of meteorological conditions of the working area, to study the direct influence of microclimate parameters of industrial premises on the body of workers, as well as to design systems for protecting the body of workers from their negative effects using the example of the use of ventilation, air conditioning and heating systems ; architectural and planning activities.

1. Meteorological conditions and their regulation in production premises

1.1 Microclimate in production premises and the influence of its indicators on the body of workers

Meteorological conditions for the working area of ​​industrial premises are regulated 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"

GOST 12.1.005 establishes optimal and permissible microclimatic conditions. With a long and systematic stay of a person in optimal microclimatic conditions, the normal functional and thermal state of the body is maintained without straining the thermoregulation mechanisms. At the same time, thermal comfort is felt (a state of satisfaction with the external environment), and a high level of performance is ensured. Such conditions are preferable in workplaces.

To create favorable working conditions that meet the physiological needs of the human body, sanitary standards establish optimal and permissible meteorological conditions in the working area of ​​the premises.

The microclimate in work areas is regulated in accordance with the sanitary rules and standards set out in SanPiN 2.2.4.548-96. Hygienic requirements for the microclimate of industrial premises."

Production premises are enclosed spaces in specially designed buildings and structures in which people’s labor activities are constantly or periodically carried out.

The workplace in which the microclimate is normalized is the area of ​​the room (or the entire room) in which labor activity is carried out during a work shift or part of it.

The work area is limited to a height of 2 meters above the level of the floor or platform where the workplaces are located.

The cold period of the year is a period of the year characterized by an average daily outdoor temperature of + 10°C and below.

The warm period of the year is a period of the year characterized by an average daily outdoor temperature above + 10°C.

Average daily outside air temperature is the average value of outside air temperature measured at certain hours of the day at designated time intervals.

Indicators characterizing the microclimate in production premises are:

Air temperature;

Surface temperature;

Relative humidity;

Air speed;

Intensity of thermal irradiation.

In addition to these basic parameters, we should not forget about atmospheric pressure P, which affects the partial pressure of the main components of air (oxygen and nitrogen), and, consequently, the breathing process.

Human life can take place in a fairly wide range of pressures, 734 - 1267 hPa (550 - 950 mm Hg). However, here it is necessary to take into account that a rapid change in pressure is dangerous for human health, and not the magnitude of this pressure itself. For example, a rapid decrease in pressure of just a few hectopascals relative to the normal value of 1013 hPa (760 mmHg) causes a painful sensation.

Indicators characterizing the thermal state of a person include body temperature, skin surface temperature and its topography, heat sensation, amount of sweat, state of the cardiovascular system and level of performance.

Microclimate indicators must ensure the preservation of the thermal balance of a person with the environment and the maintenance of an optimal or acceptable thermal state of the body.

The need to take into account the basic parameters of the microclimate can be explained by considering the thermal balance between the human body and the environment of industrial premises.

The amount of heat generated by the human body depends on the degree of physical stress in certain meteorological conditions and ranges from 85 (at rest) to 500 J/s (hard work).

The transfer of heat by the human body to the environment occurs as a result of thermal conductivity through clothing Q t, convection near the body Q k, radiation to surrounding surfaces Q and evaporation of moisture from the surface of the skin Q ex. Part of the heat is spent on heating the inhaled air Q in.

Normal thermal well-being (comfortable conditions), corresponding to this type of work, is ensured by maintaining the thermal balance:

Q=Q t +Q to +Q and +Q isp +Q in,

therefore, the temperature of human internal organs remains constant (36.0°-37.0° C). Along with changes in microclimate parameters, a person’s thermal well-being also changes. Conditions that disrupt the thermal balance cause reactions in the body that contribute to its recovery. This ability of the human body to maintain a constant temperature when microclimate parameters change and when performing work of varying severity is called thermoregulation.

In order for physiological processes in the body to proceed normally, the heat generated by the body must be completely removed to the environment. An imbalance in heat balance can lead to overheating or hypothermia of the body and, as a result, loss of ability to work, rapid fatigue, loss of consciousness and heat death.

One of the important integral indicators of the body’s thermal state is the average body (internal organs) temperature of about 36.5 °C. It depends on the degree of disturbance of the thermal balance and the level of energy consumption when performing physical work. When performing moderate to heavy work at high air temperatures, it can increase from a few tenths of a degree to 1...2°C. The highest temperature of internal organs that a person can withstand is 43 °C, the minimum is 25 °C.

Indoor air environment

Environment of protection from dangerous and harmful factors

If it is impossible to ensure human safety in the event of dangerous and harmful factors due to measures incorporated in equipment, technology, etc., then human protection means are used.

Protective equipment is a means used to prevent or reduce a person’s exposure to dangerous or harmful factors.

Based on the nature of their use, protective equipment is divided into collective protective equipment and individual protective equipment.

Collective protective equipment includes means used to protect two or more people, including

alarms, means of normalizing the air environment, lighting, protection against electric shock, etc.

Personal protective equipment includes equipment used individually, including suits, respiratory protection, hearing protection, etc.

With all the variety of remedies, they can be considered both subjective and objective.

The use of subjective ones causes a person’s defensive actions due to his conscious actions. The main types of subjective means of collective protection are automatic control devices, alarms, posters, safety signs, etc.

Objective means of protection work independently of the person ─ sound insulation, grounding, safety devices, etc.

The state of the indoor air environment is determined by meteorological conditions (microclimate) and the composition of the air, which can be polluted with gases, vapors, and dust.

They are characterized by temperature, humidity and speed of air movement in the premises. These parameters of the air environment influence heat exchange processes between the body and the air environment and human life.

In a state of rest or work, heat is generated in the human body. Moreover, the more physical (muscular) effort a person makes, the more heat is generated. A person releases the resulting heat into the surrounding space by convection, heat radiation, evaporation of sweat, and breathing. The amount of heat released and the methods of heat transfer depend on meteorological conditions, i.e. temperature, humidity and air speed. In comfortable conditions, a person gives off approximately 30% of his heat by convection, 45% by heat radiation, and 25% by evaporation of sweat and breathing. At an air temperature of more than 37°C, almost 100% of the heat generated is released through the evaporation of sweat, and at low temperatures, heat is released mainly by convection and heat radiation.

The temperature of the human body will not change if the heat generation of the body is equal to the heat transfer. This state is maintained by the body's thermoregulation.

Thermoregulation of the body is a set of heat exchange processes between the body and the environment, as a result of which body temperature is maintained at the same level. Thermoregulation is mainly carried out by changing

intensity of sweating and blood circulation. Their increase helps to increase heat transfer and maintain normal body temperature.

Under favorable meteorological conditions, due to thermoregulation, the human body temperature practically does not change. But the capabilities of the thermoregulation mechanism are limited. Under unfavorable meteorological conditions, overheating or hypothermia of the body may occur, leading to illness.

To ensure favorable meteorological conditions, standards for meteorological conditions in work premises have been established (they are also applicable for domestic premises).

Optimal and permissible temperatures, relative humidity and air speed are standardized depending on the time of year, the characteristics of production premises and the category of work performed. The standards adopt two seasons: warm, with an average daily outside air temperature of +10°C and above, and cold ─ below +10°C; three categories of work (light, moderate, heavy, respectively, with energy consumption of 172, 172-293 and more than 293 J/s); and two characteristics of premises ─ with insignificant excesses of sensible heat (23.2 J/(m³s) or less) and with significant excesses ─ more than the given values.

When monitoring meteorological conditions in rooms, air temperature is measured with thermometers, relative air humidity with psychrometers, and air speed with anemometers.

Maintaining the required meteorological conditions in the premises is ensured through ventilation, heating, air conditioning and maintaining the premises in good condition.

Heat exchange between a person and the environment. One of the necessary conditions for normal human life is to ensure normal meteorological conditions in rooms, which have a significant impact on a person’s thermal well-being. Meteorological conditions, or microclimate, depend on the thermophysical characteristics of the technological process, climate, season of the year, heating and ventilation conditions.

Human activity is accompanied by the continuous release of heat into the environment. Its amount depends on the degree of physical stress in certain climatic conditions and ranges from 85 J/s (at rest) to 500 J/s (during hard work). In order for physiological processes in the body to proceed normally, the heat generated by the body must be completely removed to the environment. An imbalance in heat can lead to overheating or hypothermia of the body and, as a result, loss of ability to work, fatigue, loss of consciousness and heat death.

One of the important integral indicators of the body’s thermal state is the average body (internal organs) temperature of about 36.5 °C. It depends on the degree of disturbance of the thermal balance and the level of energy consumption when performing physical work. When performing moderate to heavy work at high air temperatures, body temperature can rise from a few tenths of a degree to 1–2 °C. The highest temperature of internal organs that a person can withstand is +43 °C, the minimum is +25 °C. The temperature regime of the skin plays a major role in heat transfer. Its temperature varies within quite significant limits and under normal conditions the average temperature of the skin under clothing is 30–34 °C. Under unfavorable meteorological conditions in certain parts of the body it can drop to 20 ° C, and sometimes even lower.

Normal thermal well-being occurs when the heat emission Q tp of a person is completely perceived by the environment Q t o , i.e. when there is a heat balance Q tp = Q mo . In this case, the temperature of the internal organs remains constant. If the body's heat production cannot be completely transferred to the environment (Q tp > Q t o), the temperature of the internal organs increases and such thermal well-being is characterized by the concept of hot. Thermal insulation of a person at rest (resting while sitting or lying down) from the environment will lead to an increase in the temperature of the internal organs by 1.2 °C after 1 hour. Thermal insulation of a person performing moderately heavy work will cause an increase in temperature by 5 °C and will come very close to the maximum permissible. In the case when the environment perceives more heat than it is produced by a person (Q tp< Q т o), то происходит охлаждение организма. Такое тепловое самочувствие характеризуется понятием холодно.

Heat exchange between a person and the environment is carried out by convection Q k as a result of washing the body with air, thermal conductivity Q t, radiation to surrounding surfaces Q l and in the process of heat and mass transfer (Q tm = Q p + Q d) during the evaporation of moisture removed to the surface of the skin by the sweat glands Q p and when breathing Q d:

Q tp = Q k + Q t + Q l + Q tm.

Convective heat transfer is determined by Newton's law

Q k = a k F e (t surface – t os),

where αk is the convection heat transfer coefficient; under normal microclimate parameters
α k = 4.06 W/(m °C); t surface is the surface temperature of the human body (for practical calculations in winter about 27.7 °C, in summer about 31.5 °C); toc – temperature of the air washing the human body; F e – effective surface of the human body (the size of the effective surface of the body depends on its position in space and is approximately 50–80% of the geometric outer surface of the human body); for practical calculations F e = 1.8 m2. The value of the heat transfer coefficient by convection can be determined approximately as

where λ, is the thermal conductivity coefficient of the boundary layer gas, W/(m °C); δ – thickness of the boundary layer of the washing gas, m.

The boundary layer of air held on the outer surface of the body (up to 4–8 mm at air speed w = 0) prevents the transfer of heat by convection. With increasing atmospheric pressure (IN) and in moving air the thickness of the boundary layer decreases and at an air speed of 2 m/s it is about 1 mm . The lower the ambient temperature and the higher the air speed, the greater the transfer of heat by convection. Relative air humidity φ also has a noticeable effect, since the thermal conductivity coefficient of air is a function of atmospheric pressure and moisture content of the air.

Based on the above, we can conclude that the magnitude and direction of convective heat exchange between a person and the environment is determined mainly by the ambient temperature, atmospheric pressure, mobility and moisture content of the air, i.e.

Q к = f(t oc ;β;w;φ).

Heat transfer by thermal conductivity can be described by the Fourier equation:

where λ O– coefficient of thermal conductivity of human clothing fabrics, W/(m∙°C); ∆о – thickness of a person’s clothing m.

The thermal conductivity of human tissue is low, so the main role in the process of heat transportation is played by convective transfer with the blood flow.

The lower the temperature of the surfaces surrounding a person, the greater the radiant flux during heat exchange by radiation. It can be determined using the generalized Stefan–Boltzmann law:

where C pr is the reduced emissivity, W/(m 2 sti K 4); F 1 – surface area emitting radiant flux, m2; ψ 1-2 – irradiance coefficient, depending on the location and size of the surfaces F 1 and F 2 and showing the proportion of the radiant flux falling on the surface F 1 from the total flux emitted by the surface F 1; T 1 average temperature of the surface of the human body and clothing, K; T 2 – average temperature of surrounding surfaces, K.

For practical calculations in the temperature range of objects surrounding a person
10–60 °C reduced emissivity C pr ≈ 4.9 W/(m 2 K 4). The irradiance coefficient ψ 1-2 is usually taken equal to 1.0. In this case, the value of the radiant flux depends mainly on the degree of blackness ε and the temperature of the objects surrounding the person, i.e.

Q ^ = f(T op;ε).

The amount of heat given off by a person to the environment during the evaporation of moisture brought to the surface by the sweat glands is

where G n is the mass of released and evaporated moisture, kg/s; r – latent heat of evaporation of released moisture, J/kg.

Data on sweating depending on air temperature and physical activity of a person are given in Table 11. As can be seen from the table, the amount of moisture released varies within significant limits. Thus, at an air temperature of 30 °C, in a person not engaged in physical labor, moisture release is 2 g/min, and when performing heavy work it increases to 9.5 g/min.

Table 11. The amount of moisture released from the surface of the skin and from the lungs of a person, g/min

The amount of heat released into the surrounding air from the surface of the body during the evaporation of sweat depends not only on the air temperature and the intensity of work performed by a person, but also on the speed of the surrounding air and its relative humidity, i.e.

Q p =f(t os; B;w; φ; J),

where J is the intensity of labor performed by a person, W.

During the process of breathing, the ambient air, entering the human pulmonary apparatus, is heated and at the same time saturated with water vapor. In technical calculations, it can be assumed (with a margin) that the exhaled air has a temperature of 37 °C and is completely saturated.

The amount of heat spent on heating the inhaled air is

Where V LV – the volume of air inhaled by a person per unit of time, “pulmonary ventilation”, m 3/s; ρ ind – density of inhaled moist air, kg/m3; С р – specific heat capacity of inhaled air, J/(kg ˚С); t ext – temperature of exhaled air, °C; t hell – temperature of inhaled air, °C.

“Pulmonary ventilation” is defined as the product of the volume of air inhaled per breath, V in-in, m 3 by the respiratory rate per second P:

Vlv=V in-in n.

A person’s breathing rate is not constant and depends on the state of the body and its physical activity. At rest, it is 12–15 breaths per minute, and during heavy physical activity it reaches 20–25. The volume of one inhalation-exhalation is a function of the work performed. At rest, with each breath, about 0.5 liters of air enters the lungs. When performing heavy work, the volume of inhalation and exhalation can increase to 1.5–1.8 liters.

The average value of “pulmonary ventilation” at rest is approximately 0.4–0.5 l/s, and during physical activity, depending on its tension, it can reach 4 l/s.

Thus, the amount of heat released by a person with exhaled air Q t depends on his physical activity, humidity and temperature of the surrounding (inhaled) air

Q t = f(J;φ;t os).

The greater the physical activity and the lower the ambient temperature, the more heat is released with the exhaled air. As the temperature and humidity of the surrounding air increase, the amount of heat removed through breathing decreases.

Analysis of the above equations allows us to conclude that a person’s thermal well-being, or the heat balance in the person-habitat system, depends on the temperature of the environment, the mobility and relative humidity of the air, atmospheric pressure, the temperature of surrounding objects and the intensity of the body’s physical activity.

Q tp = f(t oc ;w;ψ;B;T op;J) .

Parameters - the temperature of surrounding objects and the intensity of physical activity of the body - characterize a specific production environment and are very diverse. The remaining parameters - temperature, speed, relative humidity and atmospheric pressure of the surrounding air - are called parameters microclimate.

The influence of microclimate parameters on human well-being. Microclimate parameters have a direct impact on a person’s thermal well-being and performance. For example, a decrease in temperature and an increase in air speed contribute to increased convective heat exchange and the process of heat transfer during the evaporation of sweat, which can lead to hypothermia of the body. An increase in air speed worsens well-being, as it enhances convective heat transfer and the process of heat transfer during the evaporation of sweat.

As the air temperature rises, the opposite phenomena occur. Researchers have found that when air temperatures exceed 30 °C, a person’s performance begins to decline. For humans, maximum temperatures are determined depending on the duration of their exposure and the protective equipment used. The maximum temperature of inhaled air at which a person is able to breathe for several minutes without special protective equipment is about 116 °C. Figure 10 shows indicative data on tolerance to temperatures exceeding 60 °C. Temperature uniformity is essential. Its vertical gradient should not go beyond 5 °C.

A person's tolerance to temperature, as well as his sense of heat, largely depends on the humidity and speed of the surrounding air. The higher the relative humidity, the less sweat evaporates per unit time and the faster the body overheats. High humidity at temperatures > 30 °C has a particularly unfavorable effect on a person’s thermal well-being, since almost all of the heat released is released into the environment through the evaporation of sweat. When humidity increases, sweat does not evaporate, but flows down in drops from the surface of the skin. A so-called torrential flow of sweat occurs, exhausting the body and not providing the necessary heat transfer.

Insufficient air humidity can also be unfavorable for humans due to intense evaporation of moisture from the mucous membranes, their drying out and cracking, and then contamination by pathogenic microorganisms. Therefore, when people stay indoors for a long time, it is recommended to limit the relative humidity to 30–70%.

Contrary to popular belief, the amount of sweating depends little on the lack of water in the body or its excessive consumption. A person working for 3 hours without drinking produces only 8% less sweat than if the lost moisture is fully replaced. When consuming twice the amount of water lost, there was only a 6% increase in sweat production compared to the case when water was replaced by 100%. It is considered acceptable for a person to reduce his weight by 2–3% by evaporating moisture - dehydration of the body. Dehydration by 6% leads to impaired mental activity and decreased visual acuity; evaporation of moisture by 15–20% leads to death.

Together with sweat, the body loses a significant amount of mineral salts (up to 1%, including 0.4–0.6 NaCI). Under unfavorable conditions, fluid loss can reach 8–10 liters per shift and contain up to 60 g of table salt (in total there is about 140 g of NaCI in the body). Loss of salt deprives the blood of its ability to retain water and leads to disruption of the cardiovascular system. At high air temperatures, carbohydrates and fats are easily consumed and proteins are destroyed.

To restore the water balance of workers in hot shops, replenishment points with salted (about 0.5% NaCl) carbonated drinking water are installed at the rate of 4–5 liters per person per shift. A number of factories use a protein-vitamin drink for these purposes. In hot climates, it is recommended to drink chilled drinking water or tea.

Prolonged exposure to high temperatures, especially in combination with high humidity, can lead to a significant accumulation of heat in the body and the development of overheating of the body above the permissible level - hyperthermia – a condition in which the body temperature rises to 38–39 °C. With hyperthermia and, as a consequence, heat stroke, headache, dizziness, general weakness, distortion of color perception, dry mouth, nausea, vomiting, and profuse sweating are observed. Pulse and breathing increase, the content of nitrogen and lactic acid in the blood increases. In this case, pallor, cyanosis are observed, the pupils are dilated, at times convulsions and loss of consciousness occur.

Production processes carried out at low temperatures, high air mobility and humidity can cause cooling and even hypothermia of the body - hypothermia. In the initial period of exposure to moderate cold, a decrease in respiratory rate and an increase in inhalation volume are observed. With prolonged exposure to cold, breathing becomes irregular, the frequency and volume of inhalation increases, and carbohydrate metabolism changes. The increase in metabolic processes with a decrease in temperature by 1 °C is about 10%, and with intensive cooling it can increase 3 times compared to the level of basal metabolism. The appearance of muscle tremors, in which external work is not performed and all energy is converted into heat, can delay the decrease in the temperature of internal organs for some time. The result of low temperatures is cold injuries.

Microclimate parameters also have a significant impact on labor productivity. Thus, an increase in temperature from 25 to 30 °C in the spinning shop of the Ivanovo worsted mill led to a decrease in labor productivity and amounted to 7%. The Institute of Occupational Hygiene and Occupational Diseases of the Academy of Medical Sciences of the Russian Federation found that the labor productivity of workers at a machine-building enterprise at a temperature of 29.4 °C decreases by 13%, and at a temperature of 33.6 °C by 35% compared to productivity at 26 °C.

In hot shops of industrial enterprises, most technological processes take place at temperatures significantly higher than the ambient air temperature. Heated surfaces emit streams of radiant energy into space, which can lead to negative consequences. At temperatures up to 500 °C, thermal (infrared) rays with a wavelength of 740–0.76 microns are emitted from a heated surface, and at higher temperatures, along with an increase in infrared radiation, visible light and ultraviolet rays appear.

The wavelength of the radiant flux with the maximum energy of thermal radiation is determined by Wien's displacement law (for an absolute black body)

λ Emax = 2.9∙10 3 /T.

For most industrial sources, the maximum energy comes from infrared rays (λ Emax > 0.78 µm).

Infrared rays have a mainly thermal effect on the human body. Under the influence of thermal radiation, biochemical changes occur in the body, the oxygen saturation of the blood decreases, venous pressure decreases, blood flow slows down, and as a result, disruption of the cardiovascular and nervous systems occurs.

According to the nature of their effect on the human body, infrared rays are divided into short-wave rays with a wavelength of 0.76–1.5 microns and long-wave rays with a length of more than 1.5 microns. Short-wave thermal radiation penetrates deeply into tissues and heats them up, causing rapid fatigue, decreased attention, increased sweating, and with prolonged exposure - heat stroke. Long-wave rays do not penetrate deep into tissue and are absorbed mainly in the epidermis of the skin. They can cause burns to the skin and eyes. The most common and severe eye damage caused by exposure to infrared rays is cataracts.

In addition to the direct impact on humans, radiant heat heats surrounding structures. These secondary sources release heat to the environment by radiation and convection, causing the indoor air temperature to rise.

The total amount of heat absorbed by a body depends on the size of the irradiated surface, the temperature of the radiation source and the distance to it. To characterize thermal radiation, a value called the intensity of thermal radiation is adopted. Thermal irradiation intensity JE is the radiant flux power per unit of irradiated surface.

Irradiation of the body with small doses of radiant heat is beneficial, but significant intensity of thermal radiation and high air temperature can have an adverse effect on humans. Thermal irradiation with an intensity of up to 350 W/m 2 does not cause an unpleasant sensation, at 1050 W/m 2 an unpleasant burning sensation appears on the surface of the skin after 3–5 minutes (skin temperature rises by 8–10°C), and at 3500 W/m 2 Burns may occur within a few seconds. When irradiated with an intensity of 700–1400 W/m2, the pulse rate increases by 5–7 beats per minute. The time spent in the thermal irradiation zone is limited primarily by the temperature of the skin; pain appears at a skin temperature of 40–45 °C (depending on the area).

The intensity of thermal radiation in individual workplaces can be significant. For example, at the moment of pouring steel into a mold, it is 12,000 W/m2; when knocking out castings from flasks, 350–2000 W/m2, and when releasing steel from the furnace into a ladle, it reaches 7000 W/m2.

Atmospheric pressure has a significant impact on the breathing process and human well-being. If a person can live without water and food for several days, then without oxygen - only a few minutes. The main human respiratory organ, through which gas exchange with the environment occurs (mainly O 2 and CO 2), is the trachybronchial tree and a large number of pulmonary bladders (alveoli), the walls of which are penetrated by a dense network of capillary vessels. The total surface of the alveoli of an adult is 90–150 m2. Through the walls of the alveoli, oxygen enters the blood to nourish the body's tissues.

The presence of oxygen in the inhaled air is a necessary but not sufficient condition for ensuring the vital functions of the body. The intensity of oxygen diffusion into the blood is determined by the partial pressure of oxygen in the alveolar air (P o 2, mm Hg).

The most successful diffusion of oxygen into the blood occurs at a partial pressure of oxygen in the range of 95–120 mm Hg. Art. A change in Po 2 outside these limits leads to difficulty breathing and increased stress on the cardiovascular system. So, at an altitude of 2–3 km
(Po 2≈ 70mm Hg. Art.) oxygen saturation of the blood decreases to such an extent that it causes increased activity of the heart and lungs. But even a person’s long stay in this zone does not significantly affect his health, and it is called zone of sufficient compensation. From a height of 4 km (Po 2≈ 60mm Hg. Art.), the diffusion of oxygen from the lungs into the blood is reduced to such an extent that, despite the high oxygen content ( VО 2 ≈ 21%), oxygen starvation may occur - hypoxia. The main signs of hypoxia are headache, dizziness, slow reaction, disruption of the normal functioning of the organs of hearing and vision, and metabolic disorders.

As studies have shown, satisfactory well-being of a person when breathing air is maintained up to an altitude of about 4 km, with pure oxygen (VO 2 = 100%) up to an altitude of about 12 km. For long-term flights on aircraft at an altitude of more than 4 km, either oxygen masks, or spacesuits, or cabin pressurization are used. If the seal is broken, the pressure in the cabin drops sharply. Often this process occurs so quickly that it has the character of a kind of explosion and is called explosive decompression. The effect of explosive decompression on the body depends on the initial value and rate of pressure decrease, on the resistance of the person’s respiratory tract, and the general condition of the body.

In general, the slower the rate of pressure decrease, the easier it is tolerable. As a result of research, it was found that a decrease in pressure by 385 mm Hg. Art. in 0.4 s a person endures without any consequences. However, the new pressure that occurs as a result of decompression can lead to high-altitude flatulence and high-altitude emphysema. High altitude flatulence – This is the expansion of gases present in the free cavities of the body. Thus, at an altitude of 12 km, the volume of the stomach and intestinal tract increases 5 times. High altitude emphysema, or high altitude pain is a transition of gas from a dissolved state to a gaseous state.

In some cases, for example, when working under water, in water-saturated soils, workers are under conditions of increased atmospheric pressure. When performing caisson and deep-sea operations, three periods are usually distinguished: pressure increase - compression; being in conditions of high pressure and a period of lowering pressure - decompression. Each of them is characterized by a specific set of functional changes in the body.

Excessive air pressure leads to an increase in the partial pressure of oxygen in the alveolar air, to a decrease in lung volume and an increase in the strength of the respiratory muscles necessary to produce inhalation and exhalation. In this regard, working at depth requires maintaining elevated pressure with the help of special gear or equipment, in particular caissons or diving equipment.

When working in conditions of excess pressure, lung ventilation rates decrease due to a slight decrease in breathing rate and pulse. Prolonged exposure to excess pressure leads to the toxic effect of some gases that make up the inhaled air. It manifests itself in impaired coordination of movements, agitation or depression, hallucinations, weakened memory, visual and hearing disorders.

The most dangerous period is the decompression period, during which and shortly after exiting under normal atmospheric pressure conditions can develop decompression(caisson) disease. Its essence lies in the fact that during the period of compression and exposure to increased atmospheric pressure, the body is saturated with nitrogen through the blood. Complete saturation of the body with nitrogen occurs after 4 hours of exposure to high pressure conditions.

During decompression, due to a drop in partial pressure in the alveolar air, nitrogen desaturation occurs from the tissues. Nitrogen is excreted through the blood and then into the lungs. The duration of desaturation depends mainly on the degree of tissue saturation with nitrogen (pulmonary alveoli diffuse 150 ml of nitrogen per minute). If decompression is forced, nitrogen bubbles form in the blood and other liquid media, which cause gas embolism and, as its manifestation, decompression sickness. The severity of decompression sickness is determined by the massiveness of blockage of blood vessels and their location. The development of decompression sickness is facilitated by hypothermia and overheating of the body. A decrease in temperature leads to vasoconstriction, slowing blood flow, which slows down the removal of nitrogen from tissues and the desaturation process. At high temperatures, the blood thickens and its movement slows down.

Thermoregulation of the human body. The main parameters ensuring the process of heat exchange between a person and the environment, as shown above, are microclimate parameters. Under natural conditions on the Earth's surface (sea level), these parameters vary within significant limits. Thus, the ambient temperature varies from – 88 to +60 ° C; air mobility – from 0 to 100 m/s; relative humidity - from 10 to 100% and atmospheric pressure - from 680 to 810 mm Hg. Art.

Along with changes in microclimate parameters, a person’s thermal well-being also changes. Conditions that disrupt the thermal balance cause reactions in the body that contribute to its recovery. The processes of regulating heat generation to maintain a constant temperature of the human body are called thermoregulation. It allows you to keep the temperature of the internal organs constant, close to 36.5 ° C. The processes of heat regulation are carried out mainly in three ways: biochemically; by changing the intensity of blood circulation and the intensity of sweating.

Thermoregulation by biochemical means changes the intensity of oxidative processes occurring in the body. For example, muscle tremors that occur when the body is severely cooled increases the release of heat to 125–200 J/s.

Thermoregulation by changing the intensity of blood circulation is the body's ability to regulate the flow of blood (which in this case is the coolant) from internal organs to the surface of the body by narrowing or dilating blood vessels. The transfer of heat with the blood flow is of great importance due to the low thermal conductivity coefficients of the tissues of the human body - 0.314–1.45 W/(m °C). At high ambient temperatures, the blood vessels of the skin expand, and a large amount of blood flows to it from the internal organs and , therefore, more heat is transferred to the environment. At low temperatures, the opposite phenomenon occurs: a narrowing of the blood vessels of the skin, a decrease in blood flow to the skin and, therefore, less heat is transferred to the external environment (Figure 11).

As can be seen from Figure 11, blood supply at high ambient temperatures can be 20–30 times greater than at low temperatures. In the fingers, the blood supply can change even 600 times.

Thermoregulation by changing the intensity of sweating involves changing the process of heat transfer due to evaporation. Evaporative cooling of the human body is of great importance. Thus, at t os = 18 °C, φ = 60%, w = O, the amount of heat given off by a person to the environment during the evaporation of moisture is about 18% of the total heat transfer. When the ambient temperature increases to +27 °C, the proportion of Qp increases to 30% and at 36.6 °C reaches 100%.

Figure 11. Dependence of blood supply to body tissues on ambient temperature

Thermoregulation of the body is carried out simultaneously by all means. Thus, when the air temperature decreases, an increase in heat transfer due to an increase in the temperature difference is prevented by such processes as a decrease in skin humidity, and therefore a decrease in heat transfer through evaporation, a decrease in the temperature of the skin due to a decrease in the intensity of blood transport from internal organs, and at the same time a decrease in the difference temperatures

Figures 12 and 13 show human heat balances for various amounts of work performed under different environmental conditions.

Figure 12. Thermal balance of a working person and load dependence (v – cycling speed, 1 – heat release, Q 2 – heat transfer): 1 – change in the total energy expenditure of the body; 2 – mechanical work; 3 – heat generation; 4 – change in total heat transfer (O k. Q t. O l); 5– heat given off when sweat evaporates from the surface of the body	Figure 13. Thermal balance of a working person depending on the ambient temperature (Q 1 – heat release, Q 2 – heat transfer): 1 – total energy of the body; 2– muscular work, 3 – released heat; 4 – heat transferred by conduction and convection; 5 – heat transferred by radiation; 6 – heat given off by evaporation of sweat; 7 – warmth lost with drops of sweat

The heat balance shown in Figure 12 is based on experimental data for the case of cycling at an air temperature of 22.5 °C and a relative humidity of 45%; Figure 13 shows the heat balance of a person walking at a speed of 3.4 km/h at various ambient temperatures and a constant relative humidity of 52%. The examples of the process of heat exchange between a person and the environment shown in Figures 12 and 13 are constructed under the condition that the heat balance Q tp = Q then is maintained, the maintenance of which was facilitated by the body’s thermoregulation mechanism. It has been experimentally established that optimal metabolism in the body and, accordingly, maximum labor productivity occur if the components of the heat transfer process are within the following limits: Q k + Q t ≈30%; Q d ≈ 45%;
Q p ≈ 20% and Q l ≈ 5%. This balance characterizes the absence of tension in the thermoregulation system.

The parameters of the air microclimate that determine optimal metabolism in the body and in which there are no unpleasant sensations and tension in the thermoregulation system are called comfortable or optimal. The zone in which the environment completely removes the heat generated by the body and there is no tension in the thermoregulation system is called comfort zone. Conditions under which the normal thermal state of a person is disrupted are called uncomfortable. With slight tension in the thermoregulation system and slight discomfort, acceptable meteorological conditions are established.

Hygienic standardization of microclimate parameters of industrial premises. The industrial microclimate standards are established by the system of labor safety standards GOST 12.1.005–88 “General sanitary and hygienic requirements for the air of the working area.” They are the same for all industries and all climatic zones with some minor deviations.

These standards separately standardize each component of the microclimate in the working area of ​​the production premises: temperature, relative humidity, air speed, depending on the ability of the human body to acclimatize at different times of the year, the nature of clothing, the intensity of the work performed and the nature of heat generation in the work area.

To assess the nature of clothing (thermal insulation) and acclimatization of the body at different times of the year, the concept of a period of year was introduced. There are warm and cold periods of the year. The warm period of the year is characterized by an average daily outside air temperature of +10 °C and above, the cold period -
below +10 °C

When taking into account the intensity of labor, all types of work, based on the total energy consumption of the body, are divided into three categories: light, moderate and heavy. The characteristics of production premises by category of work performed in them are established by the category of work performed by 50% or more of those working in the relevant premises.

Light work (category I) with an energy consumption of up to 174 W includes work performed while sitting or standing, which does not require systematic physical stress (the work of controllers in precision instrument making processes, office work, etc.). Light work is divided into category Ia (energy consumption up to 139 W) and category Ib (energy consumption 140–174 W). Moderate work (category II) includes work with energy consumption of 175–232 W (category IIa) and 233–290 W (category IIb). Category IIa includes work associated with constant walking, performed standing or sitting, but not requiring the movement of heavy objects; category IIb includes work associated with walking and carrying small (up to 10 kg) heavy loads (in mechanical assembly shops, textile production, processing wood, etc.). Heavy work (category III) with an energy consumption of more than 290 W includes work associated with systematic physical stress, in particular with constant movement, with carrying significant (more than 10 kg) weights (in forges, foundries with manual processes, etc.) .

Based on the intensity of heat release, industrial premises are divided into groups depending on the specific excess sensible heat. Sensible heat is the heat that affects the change in room air temperature, and excess sensible heat is the difference between the total sensible heat inputs and the total heat losses in the room. Sensible heat, which was formed within the premises, but was removed from it without transferring heat to the air of the room (for example, with gases from chimneys or with air from local suction from equipment), is not taken into account when calculating excess heat. Minor excess sensible heat is an excess of heat not exceeding or equal to 23 W per 1 m 3 of the internal volume of the room. Premises with significant excesses of sensible heat are characterized by excess heat of more than 23 W/m3.

The intensity of thermal radiation of workers from heated surfaces of technological equipment, lighting devices, insolation at permanent and non-permanent workplaces should not exceed 35 W/m2 when irradiating 50% of the human surface or more, 70 W/m2 – when irradiating 25–50% of the surface and 100 W/m2 – with irradiation of no more than 25% of the body surface.

The intensity of thermal radiation of workers from open sources (heated metal, glass, open flame, etc.) should not exceed 140 W/m2, while more than 25% of the body surface should not be exposed to irradiation and the use of personal protective equipment is mandatory.

In the working area of ​​the production premises, according to GOST 12.1.005–88, optimal and permissible microclimatic conditions can be established.

Optimal microclimatic conditions – This is a combination of microclimate parameters that, with prolonged and systematic exposure to a person, provides a feeling of thermal comfort and creates the prerequisites for high performance.

Acceptable microclimatic conditions – These are combinations of microclimate parameters that, with prolonged and systematic exposure to a person, can cause stress in thermoregulatory reactions and that do not go beyond the limits of physiological adaptive capabilities. In this case, there are no health problems, no uncomfortable heat sensations are observed that worsen well-being and reduce performance. Optimal microclimate parameters in industrial premises are provided by air conditioning systems, and acceptable parameters are provided by conventional ventilation and heating systems.

Related information.

Non-profit joint stock company

"ALMATY UNIVERSITY OF ENERGY AND COMMUNICATIONS"

Department of Labor Safety

Discipline: Basics of life safety

REPORT

for laboratory work No. 1

on the topic: “Study of meteorological conditions of industrial premises”

Speciality: 050702 – Automation and Control

Completed: students Adzhi-Khodzhaev M.A., Ereshkina K.A., Zarubin V.R. Group: AISU-07-2

Supervisor: senior teacher Prikhodko N.G.

_____________________ "____" ___________________________2010

Almaty 2010

Laboratory work No. 1. Study of meteorological conditions of industrial premises.

Purpose of the work: Determination of microclimate parameters in the working area and comparison of the obtained data with optimal standards in accordance with GOST 12.1.005-88.

Theoretical information

Monitoring the state of the microclimate in production premises is carried out by measuring microclimate parameters in the work area using the following instruments.

To determine the air temperature, mercury and alcohol thermometers), thermographs, and hot-wire anemometers are used. In the presence of thermal radiation, paired thermometers consisting of 2 thermometers are used. In one thermometer the surface of the mercury reservoir is blackened, in the other it is silvered;

To determine humidity, psychrometers are used, either without a fan or with a fan. In both cases, the psychrometer consists of 2 thermometers - dry and moistened. The thermometer is moistened by wetting the cloth covering the ball of one of the thermometers with water. In the Assmann aspiration psychrometer, the thermometers are enclosed in a metal frame, the thermometer balls are in double metal sleeves, which allows the device to be used in conditions of thermal radiation, and the use of a fan eliminates the influence of other air flows. Based on the readings of two thermometers, the empirical formula is used to calculate first the absolute and then the relative air humidity. Knowing the readings of dry and wet thermometers, you can determine relative humidity using nomograms.

To determine the speed of air movement, anemometers are used, the principle of which is based on determining the number of revolutions of a turntable rotating due to the energy of the air flow. A vane anemometer is used at air speeds from 1 to 10 m/s, a cup anemometer up to 30 m/s. Air velocity less than 1 m/s is measured with a catathermometer (or hot-wire anemometer), since a conventional anemometer in this range gives large deviations from the actual values ​​due to the inertia of the device mechanism.

Atmospheric pressure is not a standardized microclimate parameter; however, to calculate the values ​​of absolute and then relative humidity, it is necessary to know its value. Aneroid barometers of various models are used to measure atmospheric pressure.

Determination of atmospheric pressure

Determine atmospheric pressure using a barometer - aneroid VAMI, on the dial of which an arc-shaped mercury thermometer is mounted, according to the reading of which a correction for the ambient temperature is introduced. Before taking readings from the device, to eliminate the influence in the mechanism, you need to lightly tap on the body of the device. To avoid distortions during the reading, the observer's eye should be positioned perpendicular to the plane of the device. After taking the readings, it is necessary to take into account 3 corrections: scale, temperature and additional, i.e.

The correction to the instrument scale is given in Table 1

Table 1 – Correction for instrument scale

The temperature correction is determined by the formula

Where ∆Р – temperature correction by 1ºС (∆Р=0.06 mm Hg); t – temperature according to the barometer thermometer, measured with an accuracy of tenths of a degree.

The additional correction (Рdob) according to the instrument’s calibration certificate is taken equal to 13 mmHg.

Example: Using an aneroid barometer, the readings Ppr = 694 mmHg were taken. and temperature 23 ºС. The scale correction (Ршк) in accordance with Table 1 will be (-1.15) mm.Hg., temperature correction Рtemp=∆Р*t=0.06*23=1.38 mm.Hg., additional correction Рdob=13 mmHg. Then P=694-1.15+1.38+13=707.23 mmHg. There is a need to convert mm.Hg. in Pa, it must be taken into account that 1 mmHg = 133.322 Pa. The calculated value of atmospheric pressure is entered into the table. 2 research protocols.

Air temperature determination

Determine the air temperature in the laboratory using the dry thermometer of the Assmann psychrometer. Record the readings in the table. 2, 4 research protocols.

Determination of relative air humidity

Calculate the relative humidity in the laboratory using an Assmann aspiration psychrometer. To do this, 3-4 minutes before taking the readings of the dry and wet thermometers, moisten the cotton wool on the reservoir of the wet thermometer, introducing water from below, using a pipette located on the stand. Turn on the fan and turn it off after 3 minutes of operation. At the same time, the readings of dry and wet thermometers are taken, which are recorded in Table 2 of the protocol.

Determination of air speed

Determination of air speed under air showering. This is done by comparing two reports on the anemometer dial - before the start of the experiment and after the experiment. The difference between these readings is divided by the time of the experiment and then the actual speed of air movement is determined from the graph. The anemometer is located on a stand in a wind tunnel, where the air flow is created by a fan. To turn it on, you need to turn the switch on the stand to position 1. Noticeably in the report, turn on the instrument hands and stopwatch, and record the second count. To obtain more accurate results, usually take 3 measurements (100 s each), calculate the difference in the meter readings, add the results and divide by the sum of the time of all three measurements. Then, according to the calibration schedule, the average number of divisions per second is converted into speed, measured in m/s. The obtained data is entered into the table. 3.4 protocols.

Determination of sanitary and hygienic assessment of microclimate

Give a sanitary and hygienic assessment of the microclimate in the laboratory. To do this, from the current GOST-12.1.005-88 into Table 4 of the protocol, enter the values ​​of the optimal microclimate parameters for a given category of work and period of the year and those actual parameters that are determined during the work. Based on the comparison, conclusions and proposals are made about measures to create a favorable microclimate.

Table 3 - Determination of air speed

Table 4 - Comparison of the obtained data with GOST-12.1.005-88

Then the absolute ownership (A) is calculated, i.e. the amount of water vapor contained in the air at the time of the study, expressed in weight units (g/m) or as water vapor pressure in mmHg.

Where Fvl is the pressure of saturated water vapor at the wet-bulb temperature, mmHg.

0.5 – constant psychrometric coefficient;

tc-tvl – difference in readings of dry and wet thermometers, ºС;

P – atmospheric pressure, mmHg, calculated in the task using the formula.

A=11.96-(0.5*(8.8)*707.23)/755=7.84 mmHg.

C:22.8-20.822 mmHg. -Fc

Then the relative air humidity (B) is calculated as the ratio of absolute humidity to maximum (M) (the greatest possible amount of water vapor in the air at a given temperature), expressed as a percentage

Where Fc is the pressure of saturated water vapor at dry bulb temperature.

B=A/Fc*100%=7.84/20.822=37.7%

Then the relative humidity is determined according to the psychometric graph and nomogram shown on the table. The vertical lines on the graph correspond to the dry bulb readings, and the slanted ones correspond to the wet bulb readings. The desired relative humidity is defined as the point of intersection of the vertical and inclined lines corresponding to the dry-bulb and wet-bulb measurements. The resulting value is entered in Table 2, compared with the calculated value B and the difference is determined as a percentage. The discrepancy should not exceed 5%.

Table 2 – Protocol for studying microclimate parameters

Name	Meaning
1.Measuring location
2. Dry thermometer readings, ºС
3. Wet thermometer readings, ºС
4. Atmospheric pressure P, mmHg.
5. Pressure of saturated water vapor at dry thermometer temperature Fc, mmHg.
6. Pressure of saturated water vapor at dry thermometer temperature Fc, mmHg.
7. Absolute humidity value A, mmHg.
8.Relative humidity value, V,%
9.Relative humidity value according to the nomogram,%
10.Differences in the obtained values, %

Conclusion

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