The "C" coefficient changes based on the geometry of the fitting. A sharp 90-degree elbow has a much higher C-value than a radiused elbow. The DFDB provides these specific coefficients, removing the guesswork from the equation.
When air moves through a straight duct, it experiences friction loss. However, when that air hits an elbow, a transition, or a junction, the airflow is disrupted. This disruption creates turbulence, which results in a .
