Figure 4-4. Capture velocity of some representative hood types.
TYPES OF PRESSURE LOSSES
Pressure losses in airflow systems are caused by a variety of factors.
a. Friction Losses. Friction losses result from the fact that air in motion
encounters resistance along any surface confining the flowing volume. Some of the
energy of the air is given up in overcoming this friction and is transformed into heat.
The rougher the surface confining the flow or the higher the flow rate, the higher the
frictional losses will be.