This calculator is generic and can be used with SI and Imperial units. The friction coefficient can be calculated with the Colebrook equation. The default values are for air flow 20 oC, 1.2 kg/m 3 and 6 m/s - the same as in the example above. The calculator below, which is based on formula (1), can be used to calculate the pressure loss in a duct, pipe or tube if the velocity of the fluid is known.

Note! - in addition to friction loss - there is almost always minor loss in a flow. The friction coefficient is estimated to 0.019 and the length of the duct is 1 m. Example - Pressure Loss in Air DuctДЄir flows with velocity 6 m/s in a duct with diameter 315 mm. The friction coefficient can be calculated by the Colebrooke Equation or by using the Moody Diagram. The friction factor or coefficient - О» -depends on the flow, if it is laminar, transient or turbulent (the Reynolds Number) - and the roughness of the tube or duct. The Darcy-Weisbach equation is valid for fully developed, steady state and incompressible flow.

The Colebrook friction coefficient calculator corresponds to equation (1). This is important to verify when selecting friction coefficients from Moody diagrams. One is 1/4 of the other and (1) must be multiplied with four to achieve the correct result. Note! - be aware that there are two alternative friction coefficients present in the literature. ОЎ f = density of fluid (kg/m 3, slugs/ft 3) О”p major_loss = major (friction) pressure loss in fluid flow (Pa (N/m 2), psf (lb/ft 2) ) The pressure loss (or major loss) in a pipe, tube or duct can be calculated with the Darcy-Weisbach equation

Watercad v8i minor loss in pipes