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fume hood design
Fume hood is the main safety equipment in lab, most of the experiments done in ventilation cabinet, Fume hood is a special form of airtight cover, produce harmful operation process completely in the enclosure.Fume hood generally have bore can open and close operation and observation, through the study of the convulsions of Fume hood, to form a negative pressure inside ark, to prevent the ventilation equipment contained in the disturbance, the chemical reaction or heat source of hot pressing, and indoor crossflow caused the interference of harmful to escape.According to the harmful gas density and the size of the air density is different, the form of the Fume hood has a lot of, different parts of the application of different forms of Fume hood.Fume hood mainly include: the upper exhaust Fume hood, lower exhaust Fume hood, upper and lower joint exhaust Fume hood.At the same time, energy-saving and gas type Fume hood.
Fume hood cover surface wind speed is the main technical indicators of ark of exhaust air performance, it refers to the average exhaust cabinets open sliding door at the entrance to the wind speed, the selected principles of Fume hood cover face wind speed is: should not only make harmful gas cannot escape from the enclosure, and at the same time to avoid in the turbulent flow in ventilation cabinet.
High surface wind speed can lead to exhaust the workbench contained in the space above the turbulence, accumulation of pollutants may be contained in a corner, and could blow out the flame, destroy the ongoing trials, too low to cover surface wind speed is bound to cause pollutants escape, endanger the safety of test personnel.
For toxic or dangerous pests, the Fume hood the mask surface wind speed usually take 0.4 ~ 0.5 m/s.The Fume hood exhaust air according to the formula (1) [1] :
For general laboratory Fume hood, when considering the disturbance airflow inside the room and the mouth of the Fume hood operation suction speed nonuniformity, open area of the operation of large quantities of mouth to open area.
As you can see by the above formula, no adjustment system for the traditional ventilation cabinet, when the doors open operation, can satisfy the cap of 0.4 ~ 0.5 m/s surface wind speed, when the door half open or close operation, operating mask surface wind speed is greater than the design value, this will affect the operation and the effect of the exhaust air.
According to the actual test in a Fume hood [2], when fully open cupboard door, the surface wind speed 0.47 m/s, when half of cupboard door open, the surface wind speed 0.86 m/s.When the cupboard door close to close the cover face wind speed will be bigger, it will greatly affect the exhaust and experimental results.
Therefore, how to effectively control the surface wind speed is the guarantee of effective for Fume hood exhaust