Does the developed length of the duct include the transition duct?

The developed length of a duct is defined as the total length of a duct system when laid out flat. It typically measures the straight sections of the duct and does not include the transition duct, which is specifically designed to connect sections of differing sizes or shapes. Transition ducts are added to facilitate airflow between different duct dimensions but are not considered part of the "developed" length calculation. This distinction helps in accurately sizing the entire duct system for airflow calculations, pressure drops, and overall efficiency within the HVAC design.

Understanding this concept is crucial for ensuring proper duct sizing and design in HVAC systems, as it ensures the system operates effectively without unnecessary losses in efficiency. The developed length focuses on the straight run of the ducts, allowing for better airflow analysis, while transitions, though essential for system functionality, serve a different purpose in the overall design.