What is the formula for calculating pressure drop in a duct?

The formula for calculating pressure drop in a duct is rooted in the principles of fluid dynamics and reflects the impact of friction and static pressure changes along the duct's length.

In the chosen formula, pressure drop is expressed as the sum of friction loss multiplied by the length of the duct and the static pressure loss. Friction loss refers to the energy lost as air moves through the duct, primarily due to the interaction between the air and the duct's surfaces. This loss increases with the length of the duct because the air experiences more contact with the duct surface, leading to more friction.

Adding static pressure loss accounts for additional reductions in pressure that occur due to bends, fittings, or changes in the cross-sectional area of the duct, all of which can contribute to overall pressure loss in the system.

Using this formula helps HVAC professionals accurately calculate pressure losses and design systems that ensure optimal airflow, maintaining comfort and efficiency in heating and cooling systems.