A laboratory is a special place for experimental research, which can be used for experiments in biology, chemistry, physics or other special sciences. The laboratory ventilation system is one of the largest and most influential systems in the entire laboratory design and construction process. The design of its ventilation system has an important impact on the comfort of the laboratory environment, the health of experimental workers, the operation and maintenance of experimental equipment, etc., and is related to the investment cost, energy consumption and later operation costs of the laboratory.
Design and Application of Laboratory Ventilation System
The purpose of laboratory ventilation system design is to provide staff with a safe and comfortable working environment and reduce the possibility of personnel being exposed to dangerous air. Since toxic and harmful gases may be generated during the experimental operation, in order to ensure the safety of the experimenters, such experiments that may generate toxic and harmful gases are required to be carried out in the fume hood or biological safety cabinet as far as possible, and cannot be carried out in the fume hood. Local exhaust facilities, such as atomic absorption hoods, universal exhaust hoods, etc. should be provided. At the same time, the laboratory should be equipped with a comprehensive ventilation (or auxiliary exhaust) system to meet the minimum air exchange requirements of the laboratory. The design goal of the ventilation system is to make the laboratory have good ventilation effect, low noise, easy operation, energy saving, and the indoor pressure difference and temperature and humidity can keep the human body comfortable.
1. The laboratory ventilation system generally has the form of constant air volume system, double air volume system and variable air volume system
1.1. Constant air volume exhaust system
The exhaust fan adopts a single-speed fixed-frequency fan, and the exhaust air volume is basically constant. The system cannot adjust the air volume with the number of fume cupboards used and the opening height of the fume cupboard door. The advantages of this system are direct design, small investment, and simple control; the disadvantages are poor flexibility, high noise, and difficulty in ensuring the surface wind speed of the fume hood, and some toxic and harmful gases will escape from the fume hood (the surface wind speed is too small or too large). Can cause gas to escape from the fume hood), and the operating cost is high (the power consumption of the exhaust fan is maximized, and the heat energy consumption discharged by the exhaust fan is maximized).
1.2. Double air volume system
The exhaust fan adopts a two-speed fan, which performs high-low (or maximum-minimum) switching between two predetermined air flow values, which is improved compared with the constant air volume system, but does not fundamentally change the shortcomings of the constant air volume system. , is currently not widely used.
1.3 Variable air volume system
The exhaust fan adopts a frequency conversion fan, and a pressure sensor is installed on the main air duct of the exhaust or supplementary air. The static pressure controller PID is used to control the frequency converter to adjust the fan speed to achieve the purpose of constant static pressure or dynamic pressure to adjust the air volume. The high-performance airflow controller can quickly and stably adjust within a large flow range. In the variable air volume system, the fume hood is generally controlled by the surface wind speed. By using the human body sensor in front of the fume hood to detect the presence of personnel, the wind speed on the surface of the cabinet is controlled. When the operator is working in front of the fume hood, the fume hood will The surface wind speed is set to the working mode. At this time, the surface wind speed of the fume cupboard is controlled at 0.5m/s. When the operator leaves, the surface wind speed of the fume cupboard is set to the standby mode. 0.3m/s, in accordance with the requirements of JG/T222-2007 "Laboratory Variable Air Volume Fume Hood". In addition, an auxiliary exhaust is also installed in the room. When the exhaust air volume of the fume cupboard does not meet the minimum air exhaust volume requirements of the laboratory, the auxiliary exhaust air is automatically opened to ensure that the minimum air exhaust volume of the laboratory meets the standard requirements. The advantages of the automatic variable air volume control system include: significant energy saving, high safety, and easy adaptation to changing air volume requirements.
