Darcy–Weisbach equation is an empirical equation to determine the head loss, or pressure loss, due to friction for a given length of pipe to the average velocity of the fluid flow for an incompressible fluid
This formula is directly proportional to the square of the average velocity
Steps to determine the Pressure Drop through the duct
Known Quantities:
Density of the fluid, ρ
Dynamic viscosity of the fluid, μ
Hydraulic diameter of the duct, D = 2* a* b / (a + b)
Average fluid velocity, ⟨v⟩
Determine Reynolds Number: Re = ρ*⟨v⟩* D/μ
Laminar flow: Re < 2100
Turbulent Flow: Re > 4000
Determine the friction factors (Fd) as a function of friction factor and Reynolds number
Refer to the fluid Mechanics books to get different correlations for friction factor
Commonly used the Swamee-Jain Equation for turbulent flow
Determine Pressure drop per unit length of pipe (ΔP/L) in wg/ft
Pressure Drop Calculator
Enter values in the column
For hydraulic diameter:
Enter the sectional sizes (a x b) for non-circular ducts
Enter a diameter (D) directly for circular pipe
Understand the type of flow: laminar or turbulent, however, the turbulent formula has been used
