As we all know, fresh air is of great significance to human survival and health. Furniture, decorative materials, clothes and quilts, lampblack, moisture and sweat gland secretion, as well as exhaled carbon dioxide, etc. used by people at home all reduce the quality of indoor air at any time. If people live in an indoor environment that is not ventilated for a long time, they will inevitably reduce their physical fitness and cause diseases. In order to solve these problems, it is necessary to keep the indoor fresh air constantly introduced.
Room ventilation has two purposes: one is to meet the human body's demand for oxygen; the other is to remove the dirty indoor air with harmful substances. Large indoor ventilation is good, but it can't save energy. Too little ventilation can't keep the indoor air fresh and reduce the living comfort. So the best way to solve this problem is: ventilation on demand, continuous micro.
(I) local exhaust
In the local place where the harmful substances are concentrated, a catching device is set to discharge the harmful substances so as to control the diffusion of the harmful substances into the room. This ventilation method is called local exhaust. This is the most effective ventilation method for gas prevention and dust removal. The local exhaust system consists of the following parts:
(1) local exhaust hood
The local exhaust hood is used to catch harmful substances. Its performance has a direct impact on the technical and economic indicators of the local exhaust system. The local exhaust hood with good performance, such as airtight hood, can get good working effect as long as the air volume is small. Due to the difference of production equipment and operation, the forms of exhaust hood are various.
(2) air duct
The pipe for conveying gas in the ventilation system is called the air pipe, which connects various equipment or components in the system into a whole. In order to improve the economy of the system, the gas velocity in the air duct should be reasonably selected, and the pipeline should be as short and straight as possible. Air ducts are usually made of smooth surface materials, such as steel sheet, PVC plate, and sometimes concrete, brick and other materials.
(3) dust removal and purification equipment
In order to prevent air pollution, when the amount of harmful substances in the discharged air exceeds the emission standard, purification equipment must be used for treatment. When the emission standard is reached, the air will be discharged. The purification equipment is divided into dust remover and harmful gas purification device.
The fan captures the power of air flow to the mechanical exhaust system. In order to prevent the abrasion and corrosion of the fan, it is usually placed behind the purification equipment.
(II) local air supply
Supply air to the local working place, so as to create a good air environment in the local area. It is difficult, uneconomical and unnecessary to improve the air environment of the whole workshop with comprehensive ventilation for the workshop with large area and few operators. For example, in some high-temperature workshops, it is not necessary to cool down the whole workshop, only to supply air to individual local working places, and create a good air environment in local places. This ventilation method is called local air supply. Local air supply is mainly used for local cooling, and it can be divided into two types: systematic type and decentralized type.
1. Systematic air supply system
The system type is the ventilation system to send the outdoor air to the work place. Fig. 3-1-2 is a schematic diagram of a systematic local air supply system for the pouring section of the casting workshop. After centralized treatment, the air is sent to the local working area. Decentralized local air supply usually uses axial flow fans or spray fans, and uses indoor recirculating air.
(III) overall ventilation
Comprehensive ventilation is to ventilate the room to dilute indoor harmful substances, eliminate residual heat and temperature, and make it meet the requirements of health standards.
The power of overall ventilation can be natural wind pressure and thermal pressure, or fan wind pressure. The specific implementation methods of comprehensive ventilation can be divided into comprehensive exhaust method, comprehensive air supply method, comprehensive exhaust and air supply method, comprehensive air supply method, local exhaust and mixed method, etc. different methods can be adopted according to the actual situation of the workshop.