fans Flashcards
3 types of pressure from fans
static
velocity
total pressure
airflow through the system is controlled by this
damper
type of pressure that air exerts on the inside of duct walls
static
type of pressure measured at fan discharge with ducting 90 degrees
static
type of pressure caused by air flowing through a duct and is felt only by the surfaces that the air actually strikes
velocity
type of pressure measured by connecting one end of the manometer at right angles to the duct wall and the other end with the opening facing the airflow
velocity
pressure conversion static to velocity
decreasing cross sectional area
converging
pressure conversion velocity to static
increasing cross sectional area
diverging
mechanical draft type where pressure in the furnace is below atmospheric pressure.
Fan located between the boiler and the chimney
induced draft
centrifugal blade fan most effecient and require less horsepower
backward incline blade fan
centrifugal blade fan has a lower speed for the same volume, low speed good for hvac application
forward blade fan
centrifugal blade fan are used where high speed requires a stronger wheel
radial blade fan
centrifugal fan casing cause this pressure change
velocity of static
advantage of axial flow fans
low cost
compactness
axial fans should not be used in these system
ducted air distribution system