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INDUSTRIAL VENTILATION DUST COLLECTION SYSTEM DESIGN
HOOD DESIGN
Proper design of exhaust hoods is a must If you want effectively
control athmospheric contanimation at its source with minumum
air flow and power
consumption.The theory of capture velocity depends on the creation
of air flow past the source of contaminant sufficent to remove
highly contaminated
air around the source and to draw air into an exhaust hood.
| Where ; |
| Capture Velocity |
V |
fpm |
Air velocity at any point in
front of the hood or at the hood opening ,neccesary to capture
the contaminated air at that poinby causing it to flow into
the hood. |
| |
|
|
|
| Face Velocity |
Vf |
fpm |
Air velocity at the hood opening |
| |
|
|
|
| Slot Velocity |
Vs |
fpm |
Air velocity through the openings in a slot
type hood |
| |
|
|
|
| Plenum Velocity |
Vp |
fpm |
Air velocity in the plenum |
| |
|
|
|
| Duct Velocity |
Vd |
fpm |
Air velocity through the duct after hood. |
| |
|
|
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| Transport Velocity |
Vt |
fpm |
Minumum air velocity through the duct required
to move particules in air stream. |
| |
|
|
|
| Dust Distance |
X |
ft |
Distance outward along center axes of hood. |
| |
|
|
|
| Air Flow |
Q |
cfm |
Required minumum air flow to capture dust
particles |
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|
|
| Area |
A |
ft2 |
Area of hood opening |
| |
|
|
|
| Diameter |
D |
ft |
Diameter of round hoods |
Dust Exhaust
system Hood Entry Losses Table
Back
Dust Explosions
A dust explosion is very similar to a gas or vapour cloud explosion,
i.e. when a volume of a flammable mixture is ignited, resulting
in a rapid pressure increase and fire moving through the cloud.
A dust explosion occurs when a combustible material is dispersed
in the air forming a flammable cloud and a flame propagates through
it. This of course also depends on the supply of oxygen to the
fire, and the concentration of the fuel, if either of these are
in too high or low then the explosion will not occur.
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