What size round duct is required for an airflow rate of 1,400 cfm and .1 friction?

To determine the correct size of round duct required for an airflow rate of 1,400 cubic feet per minute (cfm) with a friction loss of 0.1 inches of water column, one must consider the relationship between airflow, duct size, and the pressure drop created by friction in the duct.

For a specific airflow rate, the duct size must be adequate to transport the air efficiently without excessive friction loss. The duct size influences the velocity of the air traveling through it, which in turn affects the friction loss.

In HVAC applications, a common practice is to use ductulator or duct sizing methods which relate airflow rates to duct sizes, given a certain friction rate. In this case, for a 1,400 cfm airflow at 0.1 inches of friction loss, calculations indicate that a 16-inch round duct would be sufficient to handle the airflow without exceeding the acceptable pressure drop.

This is backed by duct sizing charts and tables used in HVAC design, which provide the optimal duct diameters for specific airflow rates and friction losses. A 16-inch duct generally correlates well with the desired airflow while maintaining efficiency and minimizing noise and turbulence in the duct system.

Selecting a larger or smaller diameter duct could lead to issues such as increased