Calculating Losses

Dynamic Losses The pressure loss in each fitting, inlet and outlet must be calculated separately and is based on the velocity of air at that point in the system.

Friction Losses Friction Loss Charts are designed to give the pressure loss due to friction in the duct. To determine pressure loss, use the following formula:

C = Loss coefficient V = Air velocity in feet/minute L = length in feet O = perimeter in feet Q = air quantity in 100,000 cfm (60,000 cfm would be .60) * air density (.075 at sea level) in lb/ft3	A = area of duct in square feet K=the friction factor for the duct material (Fiberglass is 11.7; Steel is 12; Cassette duct is 15; Layflat duct is 18; Flexible Suction duct is 27)