Air Flow (CFM) & Duct Sizing Calculator
This calculator assists in determining air flow rates, duct dimensions, and estimating friction losses and fan power for HVAC duct systems. It supports both circular and rectangular duct geometries.
Key Inputs:
- Air Flow Rate (\(\dot{Q}\)): Volume of air moved per unit time.
- Air Velocity (\(V\)): Speed of air within the duct.
- Duct Dimensions: Diameter for circular, Width & Height for rectangular ducts.
- Duct Length (\(L\)): Total length of the duct run for friction loss calculation.
- Air Density (\(\rho_{air}\)): Density of air at operating conditions.
- Air Dynamic Viscosity (\(\mu_{air}\)): Dynamic viscosity of air at operating conditions.
- Duct Roughness (\(\epsilon\)): Absolute roughness of the duct material.
- Fan-Motor Efficiency (\(\eta_{fan}\)): Overall efficiency of the fan and motor system.
Calculated Outputs:
- Duct Cross-sectional Area (\(A\)): Area of the duct perpendicular to flow.
- Air Velocity (\(V\)): Calculated air speed.
- Air Flow Rate (\(\dot{Q}\)): Calculated volume flow rate.
- Hydraulic Diameter (\(D_h\)): Equivalent diameter for non-circular ducts.
- Reynolds Number (\(Re\)): Dimensionless number indicating flow regime.
- Friction Factor (\(f\)): Dimensionless coefficient used in friction loss calculations (using Haaland equation).
- Friction Loss per Unit Length (\(\Delta P_f/L\)): Static pressure drop per meter or 100 ft of duct.
- Total Friction Loss (\(\Delta P_{total}\)): Total static pressure drop over the specified duct length.
- Estimated Fan Power (\(P_{fan}\)): Approximate electrical power required by the fan.
Calculation Results
| Parameter | Value |
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