Engineering calculators

Darcy–Weisbach pressure loss

Pipe length (m)Inside diameter (mm)Flow rate (m³/h)Roughness (mm)Density (kg/m³)Dynamic viscosity (mPa·s)

ΔP = f(L/D)(ρv²/2). Laminar: f = 64/Re. Turbulent (Swamee–Jain): f = 0.25/[log₁₀(ε/(3.7D) + 5.74/Re⁰·⁹)]².

Vertical depth (m)FluidCustom densityCustom unit

P = ρgh, with g = 9.80665 m/s². Gauge pressure excludes atmospheric pressure.

Initial volume (m³)Initial absolute pressure (bar)Initial temperature (°C)Final absolute pressure (bar)Final temperature (°C)

P₁V₁/T₁ = P₂V₂/T₂ → V₂ = V₁(P₁/P₂)(T₂/T₁). Temperatures use kelvin; pressures must be absolute.

Initial investmentAnnual net cash flowProject life (years)Discount rate (%)

NPV = −I + Σₜ₌₁ⁿ CF/(1+r)ᵗ. Simple payback = I/CF; payback ignores discounting and cash flows after recovery.