Duct Friction Loss Calculator
The Duct Friction Loss Calculator is a tool used to estimate the pressure drop that occurs in a straight section of ductwork due to friction between the moving air and the duct's interior surfaces. Understanding and calculating friction loss is crucial for proper HVAC duct system design, as it directly impacts fan selection and overall system efficiency. This calculator typically requires inputs like airflow rate (CFM), duct dimensions (diameter for round, or width and height for rectangular), duct length, and duct material (which determines roughness). The results are usually expressed as inches of water gauge (in. wg) per 100 feet of duct.
Minimizing Duct Friction Loss: High friction loss in ductwork forces the fan to work harder, increasing energy consumption and potentially reducing airflow. To minimize friction loss: ensure proper duct sizing (avoid undersized ducts), use smooth interior surfaces (metal ducts generally have lower friction than flex ducts; if using flex duct, ensure it's pulled taut), minimize fittings (elbows, tees, transitions add to total loss), keep duct runs short and direct, and seal all joints to prevent air leaks.
This calculator uses highly simplified formulas and generic factors for friction loss estimation. It does NOT account for fittings (elbows, tees, transitions), dynamic losses, or precise Reynolds number-dependent friction factors (e.g., from Moody chart or Colebrook equation). For accurate duct system design, always use comprehensive methods like ACCA Manual D, SMACNA guidelines, or specialized duct design software.