Build a duct system resistance curve (H vs Q), overlay a fan curve, and find the operating point. Includes density correction for altitude and temperature.
Air conditions
Duct segments
Fan curve (optional — enter H-Q points)
System curve: ΔP_sys = R·Q² + ΔP_static. R is the sum of segment resistances (friction + minor losses) referred to flow rate.
Duct roughness assumed ε = 0.09 mm (galvanised steel). Air kinematic viscosity ν ≈ 1.5×10⁻⁵ m²/s used for all segments.
Duty point found by interpolated intersection of system and fan curves. Supply manufacturer fan data for accurate selection.