Duct Sizing Methods

Duct sizes are calculated using either the equal friction method or constant velocity method. For more information, see Specifying a Calculation Method for Duct Sizing.

The calculations for duct friction losses are based on the Darcy and Altshul-Tsal equations described in the 2001 ASHRAE Fundamentals Handbook, Chapter 34, as follows:

The Add Ducts dialog shows an asterisk next to the Velocity field to indicate that the constant velocity method was used to calculate duct size.

The Modify Duct dialog shows the fixed parameter value for velocity that was used to calculate duct size.

Duct sizes are calculated based on the flow values assigned to all outlet devices detected in the system. For more information on assigning flow values, see Configuring Mechanical Parts for Analysis.