Safety Health and Environmental calculations

Calculate flow rate when gas flow rate (velocity) is 100 fpm in a round duct with 4 inch radius.

First calculate area of duct x-section.

A= 3.14 *r^2 = 3.14 * (4/12)^2 = 0.35 ft^2

Q or CFM, cubic feet per minute = V (in ft/min) * area in ft^2

= 100 ft/min *0.35

= 35 cubic ft/min