Bilgin CANDEMİR (YTU. MYO LECTURER MECHANICAL ENG. BUSINESS HR. MSC.)
GENERAL VENTILATION AND AIR CONDITIONING
Ambient Air Quality; The necessary air quality must be provided for the health and safety of employees in the workplace.
Factors Affecting Ambient Air Quality are; Air temperature, Air humidity, Air flow speed, Pollutant elements in the air. The basic condition required for the health of employees is provided by keeping body temperature at a normal level and removing pollutants from the environment.
In order to provide this balance, appropriate and sufficient ventilation is an important measure to be taken in the environment. When evaluated together with the features of ventilation, heating, cooling and humidification, it is an important part of workplace air conditioning. In this respect, ventilation ensures that the working environment is satisfactory for both production and product, as well as the thermal comfort of the employees.
Ventilation is a measure to protect employees from the negative effects of heat and air pollutants by reducing the temperature of the work environment and the level of air pollutants that employees have to breathe.
Ventilation is examined in two groups as general ventilation and local ventilation. The sources that cause the temperature of the working environment to increase are; the work done in the workplace, external factors, employees, sources of pollution in the working environment air, the work done in the workplace, external factors, characteristics of the work, etc.
Factors that pollute the working environment air consist of chemical, physical, and biological factors. Ventilation is the process of simultaneously removing the air in the working environment and replacing it with fresh air. However, in some cases, providing adequate ventilation is done by moving the ambient air.
In industrial environments where flammable gases are used or emitted, this type of ventilation is necessary to prevent flashover. Ventilation is a very useful tool for controlling heating and pollution.
Because the high heat (a significant part) of the pollution that occurs in the workplace working environment is transmitted to the employees via air. The heat in the ambient air is stored in the gases that make up the air, and the gases, dust and other pollutants that make up the air pollution that occurs in the working environment are mixed with the air. For these reasons; the processes of distributing the heat and pollution in the ambient air and removing them from the environment are more or less the same.
The dispersion of heat and pollution in the ambient air occurs through mixing caused by wind, forced ventilation and turbulence created by machine movements. The type and amount of ventilation required to provide air that meets quality standards in workplaces depends on two factors: the speed at which heat and pollution spread and disperse the heat and pollution is diluted or removed from the environment by ventilation. Two important issues that are important to research and understand are; how heat and pollution are mixed and how clean air will dilute or remove heat and pollution from the environment.
There are three areas to consider: determining the location of the air current that is directed into or will be created within the work environment, determining the areas where the air currents will mix, and determining the areas where the air will be expelled from the environment.
There are two types of air flow: heat and dirty air from machines or work. Fresh air flow from existing openings in the environment. The speed of the air flow; when it mixes with the surrounding air, it gradually speeds up or slows down depending on the existing air in the environment.
If the speed of the air flow is the same as the speed of the existing air moving in the environment, the flow becomes unnoticeable. The areas where the air leaves the working environment are windows, doors, ceiling fans, exhaust vents and grilles.
Although the air coming out of such dischargers has a high density, its speed decreases near the air outlet. As a result, a draft is created around the openings that provide the discharge. Therefore, the discharge outlets can be uncomfortable for the workers, since they themselves create a reciprocal draft.
However, if the exhaust vents are placed too close to the source, the spread over large areas is reduced. The principles of venting heat, gases and dust, as well as the rate and physical properties of hot air pollution, should be studied.
Density differences resulting from heat cause different air currents to shift. Polluted gases and vapors are heavier than air when stationary, but when they encounter air, the density differences become less pronounced.
VENTILATION TYPES
Natural ventilation: Natural ventilation is used to dilute and disperse heat and polluted air.
Air is released from any opening in the surface boundaries of a space and replaced by fresh air. Therefore, the hot or dirty air inside is diluted. It is difficult to determine the amount of natural ventilation that provides fresh air through infiltration, because this rate depends on the wind pressure from outside, the direction of the wind, the radiation of solar rays, the number and size of cracks in the walls and roofs, and the moving air in the interior.
As a result, the natural ventilation method has always been found useful for controlling the spread of dust and smoke. With this method, only very low concentrations of gas and vapor can be controlled. This method is used only in environments where the ambient temperature is not high and no other method is required.
Dilute ventilation: Dilute (forced) ventilation is used to replace natural ventilation. However, high temperature and high gas and vapor concentrations are required in the environment.
This is done by blowing air into the space or by installing fans on the walls and ceiling. In both cases, heat and pollution are diluted and removed from the building.
Air conditioning; Air conditioning systems perform heating, cooling and humidification functions together. Meanwhile, some systems also eliminate air pollutants.
These systems are classified into three groups according to their working principles. ◦ 1-Closed systems. ◦ 2-Semi-closed systems. ◦ 3-Partitioned systems.
Air conditioning systems are divided into two groups according to the areas they affect; ◦ A-For single areas, ◦ B-For multiple areas.
Common elements of air conditioning systems are as follows; ◦ a- Heating and cooling unit ◦ b- Water or refrigerant gas ◦ c- Electric or other fuel systems ◦ d- Humidity control unit ◦ e- Direct water vapor injection ◦ f- Condensation units ◦ g- Solids holding units
HEAT (AIR TEMPERATURE): In the human body, some physical and chemical values such as heat, salt, acid, base, sugar etc. must remain within certain limits. The human body has mechanisms in its structure that ensure and adjust these values within certain ranges. With these mechanisms, humans defend themselves against adverse environmental conditions and provide the opportunity to continue their lives even in adverse conditions.
One of these balances in the human body is heat (Temperature). The temperature of a normal human body that is not sick is 36 degrees centigrade. Humans are in constant communication with their environment. They are constantly affected by the conditions around them. One of the environmental conditions of humans is air temperature. If the air temperature in the environment is high, the human body begins to warm up due to the heat transfer from the hot environment to the cold environment (Heat transfer).
The human body temperature must remain around 36 degrees Celsius. Otherwise, our fever rises and we fall into bed. Similarly, if the ambient temperature is too low, the body's temperature begins to drop due to heat transfer and we begin to freeze.
The human body tries to keep the body temperature constant with defense systems that we do not know the details of, such as contracting and shivering when the air in the environment cools down, and opening and sweating when the air warms up. However, while these defense mechanisms are working, the person becomes bored and uncomfortable, and their work efficiency decreases. If the environmental conditions are deteriorated too much, the body can no longer defend itself, the defense mechanisms fail or become inadequate, the person's balance is disrupted, their body chemistry is disrupted and they get sick. This invites accidents.
It is necessary to make the environmental conditions and the temperature, which is our topic, suitable for the employees so that they do not get bored, uncomfortable, get sick, and their body chemistry is not disrupted.
AIR FLOW SPEED In order to expel the dirty air formed in the workplace and replace it with clean air, there must be appropriate ventilation, and therefore an appropriate air flow, in the environment. However, if this air flow exceeds 0.5 meters/second, disturbing breezes occur. Due to the harms of these breezes, we very often encounter that the ventilation systems are not operated in workplaces, especially in welding workshops, even though the air in the environment is dirty. In order to avoid such negativities, HEATING AND VENTILATION SHOULD BE UNDERSTOOD AS AIR CONDITIONING and projects should be designed with this understanding, taking all values into consideration. Now let's focus on the relationships between temperature, humidity, air flow speed and radiant heat. ◦ An attempt was made to determine the conditions in which the majority of the employees (80%) feel most comfortable in terms of heat sensation in workplaces. In this way, the concept of THERMAL COMFORT ZONE emerged. ◦ Thermal Comfort Zone; It is the region between the upper and lower limits of the thermal comfort conditions required for the employee to be in the most comfortable position while performing his/her activity. Our occupational health and safety legislation includes direct and indirect provisions related to both ventilation and air conditioning. The main statutes and regulations containing these provisions and the aforementioned provisions are listed below. Former Occupational Health and Safety Regulation issued based on Article 74 of Law No. 1475, which was repealed as a result of the gradual entry into force of the temporary second article of Law No. 4857, Article 6331 - Source, Regulation on the Protection of Employees from the Dangers of Explosive Atmospheres Regulation on Health and Safety Measures to be Taken in Workplace Buildings and Annexes Regulation on Health and Safety Measures in Working with Chemical Substances Regulation on Manual Handling Works Regulation on Health and Safety in Construction Works Old Occupational Health and Safety Regulation - Source can be used. Article 8. The air volume in workplaces, including the volumes occupied by machinery, materials and similar facilities, shall be at least 10 cubic meters per worker. In calculating the air volume, ceiling heights exceeding 4 meters shall not be taken into account. Article 20. It is essential that the temperature and humidity in closed workplaces are moderate, while being suitable for the nature of the work being done.
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