On civil building ventilation technology and development?

Entering the end of the 20th century, with the rapid development of China's economic construction, a large number of new buildings appeared, the vast majority of which are civil buildings, as HVAC technicians are often exposed to the heating of these buildings, ventilation, air apnea, fire and smoke exhaust problems. Ventilation can dilute indoor pollutants or odors; exclude a variety of indoor pollutants; provide people to breathe the oxygen needed and combustion; eliminate pollutants at the same time, can be eliminated to a certain extent indoor residual heat, residual moisture. Civil building ventilation technology research and application has become very urgent and necessary.

Comprehensive ventilation and local ventilation

Comprehensive ventilation, also known as dilution ventilation, it is the whole workshop or room ventilation, in order to change the indoor temperature, humidity and dilute the concentration of hazardous substances, and constantly the contaminated air to the outdoors, so that the operating area of the air environment in line with the requirements of health standards. According to the different direction of airflow, comprehensive ventilation can be divided into comprehensive air supply and comprehensive exhaust. According to the different ways of ventilation, comprehensive ventilation is divided into natural ventilation, mechanical ventilation or natural ventilation and mechanical ventilation combined use and other ways. Comprehensive ventilation is when the source of harmful substances is not fixed, or local ventilation after the concentration of harmful substances still exceeds the standard when the ventilation of the entire room. According to its role in different mechanisms, but also divided into: (1) dilution ventilation, also known as mixed ventilation, that is, than the indoor pollutant concentration of air and indoor air mixing, so as to reduce the concentration of indoor pollutants, so that it meets the health requirements. (2) replacement ventilation replacement ventilation system initially began in Northern Europe, and now has some applications in China. In the replacement ventilation system, fresh cold air from the bottom of the room at a very low speed into the air temperature difference of only 2-4 ℃. Incoming fresh air due to high density and diffuse like water throughout the bottom of the room, the heat source caused by thermal convection airflow indoor vertical temperature gradient, the airflow slowly rise out of the work area, the residual heat and pollutants pushed to the top of the room, and finally located in the ceiling or at the top of the room directly discharged from the exhaust port. Indoor air approximate piston-like flow, so that the pollutants with the air flow from the top of the room, the work area is basically in the incoming air, i.e., the concentration of pollutants in the work area is approximately equal to the concentration of the incoming air, which is the biggest difference between the replacement ventilation and the traditional dilution of the overall ventilation. Obviously, the ventilation effect of replacement ventilation is much better than dilution ventilation.

Local ventilation is a local area of the room ventilation to control the spread of pollutants in the local area, or in the local area to obtain a better air environment, that is, local exhaust and local air supply. For example, the exhaust of the kitchen stove is a typical local exhaust. The scope of local ventilation is limited to the formation of harmful substances in a more concentrated place, or staff often active local area of the ventilation method, known as local ventilation. Local ventilation system is divided into two categories of local air supply and local exhaust, they are the use of local airflow, so that the workplace is not contaminated by harmful substances to improve the air conditions of the workplace. The scope of local ventilation is limited to the formation of harmful substances in a more concentrated place, or the staff often activities in the local area of the ventilation method, known as local ventilation. Local ventilation system is divided into two categories of local air supply and local exhaust, they are the use of local airflow, so that the workplace is not contaminated by harmful substances to improve the air conditions at the workplace.

Mechanical ventilation and natural ventilation

Mechanical ventilation and natural ventilation in civil buildings are common forms of ventilation, but the mechanical ventilation system relies on the fan to provide the pressure required for air flow, while the natural ventilation is to rely on the role of wind pressure and heat pressure to make the air flow. Mechanical ventilation systems include mechanical air intake system and mechanical exhaust system, local air supply and local exhaust system.

Natural ventilation is a kind of non-consumption of power to obtain a larger air volume of the most economical ventilation methods, if possible should be utilized as much as possible. The role of natural ventilation principle, in Chapter 7 has been described, and will not be repeated. It should be noted that the role of natural ventilation is complex and variable, especially for high-rise buildings, complex shape of the building is more so, not in the windward side of the wind into the wind, the leeward side of the wind will certainly exhaust. For high-rise buildings, natural ventilation in the heat pressure and wind pressure plays a large role in the heating load calculation should pay attention to the cold air infiltration of heat consumption and external doors open the cold air invasion of heat consumption increases. In addition, due to the presence of heat pressure, wind pressure, high-rise buildings, elevator shafts, stairwells, etc. will produce a "chimney effect", which is very detrimental to the fire smoke.

Conclusion

The main sources of indoor pollutants in civil buildings exist in various aspects, including people and their activities; building materials; pets; furniture, daily necessities and so on. Harmful factors of indoor pollutants include toxicity; radioactivity; potential to cause colds, allergies, dermatitis, etc.; and the production of unpleasant odors. Ventilation and air conditioning technology is solving the regulation and control of the air environment, to the overall regulation and control of the quality of the environment of the internal space to the development of ventilation and air conditioning will be more and more widely used, ventilation and air-conditioning technology, the development of the future is bright and broad.

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