How to design laboratory ventilation system?
Release time:2019-11-11 source:
How to design laboratory ventilation system? Edu purification gives you specific answers:
I. laboratory ventilation device:
1. Universal suction hood is the first choice for local ventilation: simple installation, flexible positioning, good ventilation performance, which can effectively protect the personal safety of laboratory staff; 2. Atomic absorption hood is mainly suitable for all kinds of large-scale precision instruments, requiring positioning installation, with set ventilation performance number, which is also one of the factors that must be considered in the overall laboratory planning; 3. Exhaust hood It is mainly suitable for chemical laboratory. It is one of the necessary equipment in solving the overall ventilation requirements of this kind of laboratory.
4. The main fans used in the laboratory are axial fans (diagonal fans, pipeline fans) and centrifugal fans. Axial flow fan is suitable for ventilation system with small wind pressure and short pipeline (generally within 10m, otherwise it is easy to cause immobility); centrifugal fan is suitable for ventilation system with long pipeline (generally beyond 10m, otherwise it is easy to cause noise). Fan material: generally divided into FRP, PP, PVC, iron sheet, etc., of which FRP is more. The selection of fan model is based on air volume and air pressure.
2. Design and calculation of air volume 1. Calculation method of air volume: determine the exhaust air volume according to the surface air speed (the general value of the surface air speed is 0.3 ~ 0.5 m3 / h). Calculation formula: g = s · V · h · μ = l · h · 3600 · μ, of which
G: exhaust air volume s: operation window opening area V: face wind speed H: time (1 hour) l: fume hood length H: operation window opening height μ: safety factor (1.1 ~ 1.2) example: the exhaust air volume of 1200L fume hood is calculated as follows: G: 1.2 * 0.75/2 * 0.8 * 3600 * 1.2 = 1555 m3 / h empirical value:
The exhaust volume of 1200L fume hood is generally 1500 m3 / h, and that of 1500L fume hood is generally 1800 m3 / h, and that of 1800l fume hood is generally 2000 m3 / h
Note: the calculation method of exhaust air volume of exhaust hood on the central platform is the same as that of the ventilation cabinet. The calculation method of exhaust air volume of atomic absorption hood: determine the exhaust air volume according to the air speed of the hood (the general value of the air speed of the hood: 1 ~ 2 m3 / h). The calculation formula: g = π r? 2? V? 3600? μ
G: exhaust air volume R: cover radius V: cover air speed μ: safety factor (1.1 ~ 1.2) empirical value: in general, the exhaust air volume calculation formula of the overall ventilation of the atomic absorption hood in the range of 500 ~ 600 m3 / h: g = V · n · H = L · w · h · n · h where
G: exhaust volume
V: room volume n: ventilation times (generally 8-12 times)
H: time (1 hour)
Reference value of air change times laboratory chemical organic synthesis toxic experiment P-Level experiment biomedical physical times / hour 6-20 15-18 20-30 15-30 5-30 5-10 3-8
2. The resistance of the calculated wind pressure along the pipeline is about 5pa / m, that of the elbow is 10-30pa / piece, and that of the tee is 30-50pa / piece Note: the sum of all resistances multiplied by the safety factor (1.1 ~ 1.2) is the wind pressure value.
3. Calculation of air volume of ventilation pipeline note: generally, the value range of air speed of national standard is v = 6 ~ 8m / S (the value range of air speed of company's calculation standard is v = 8 ~ 12m / s). Calculation formula: g = s · V · 3600 = π R ² · V · 3600 → r = [g / (π · V · 3600)] where
G: exhaust air volume (calculated according to the above)
R: duct radius
V: wind speed of air duct note: the dimensions of rectangular air duct are as follows: 120, 150, 200, 250, 300, 400, 500, 630, 800, 1000, 1200, 1400, 1600, 1800 (if it is necessary to change from circular pipe to rectangular pipe, the design principle is equal area)
Reference value for air volume calculation of some ventilation pipelines type specification (mm) exhaust air volume m3 / h round air duct Φ 160 578.76 Φ 200 904.32 Φ 300 2034.72 Φ 400 3617.28 rectangular air duct 200 * 200 1152 300 * 300 2592 400 * 400 4608
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