ENGINE INSTALLATION & SERVICE HANDBOOK Caterpillar

Before the duct cross-sectional area can be calculated you must determine two elements.

Qcfm = Amount of Ventilation air and Combustion air (combine system) in cfm.

Va = Desired inlet air velocity [Not to exceed 2,000 feet per minute (609.6 m/min)]

Once these two elements have been determined then the following formula can be used to determine the minimum cross-sectional for both intake and exhaust ducts or openings.

Av = Duct cross sectional area in square inches (mm)

Q_a = Quantity of air flow in cubic feet per minute (m³/min)

V_a = Velocity of air in the duct in feet per minute (m/min)