Ductulator
The Ductulator is an interactive tool for sizing ductwork based on airflow and design parameters.
Duct Sizing Basics
Section titled “Duct Sizing Basics”Key Parameters
Section titled “Key Parameters”Airflow (CFM or L/s)
Section titled “Airflow (CFM or L/s)”The volume of air flowing through the duct.
Velocity (FPM or m/s)
Section titled “Velocity (FPM or m/s)”The speed of air in the duct. Higher velocity means:
- Smaller duct size
- More noise
- Higher pressure drop
Friction Rate
Section titled “Friction Rate”Pressure drop per unit length (in. wg/100 ft or Pa/m).
Duct Size
Section titled “Duct Size”Resulting dimensions:
- Round: diameter
- Rectangular: width × height
Using the Ductulator
Section titled “Using the Ductulator”Input Parameters
Section titled “Input Parameters”Enter design values:
- Required airflow (CFM)
- Target friction rate or velocity
- Duct shape (round or rectangular)
Sizing Method
Section titled “Sizing Method”Velocity Method
Section titled “Velocity Method”Size based on target velocity:
- Enter CFM and target velocity
- Calculate required duct area
- Show resulting duct size
Equal Friction Method
Section titled “Equal Friction Method”Size based on friction rate:
- Enter CFM and friction rate
- Use friction chart
- Show velocity and duct size
Round Ducts
Section titled “Round Ducts”For circular ducts:
- Enter airflow
- Set friction or velocity target
- Get diameter
Rectangular Ducts
Section titled “Rectangular Ducts”For rectangular ducts:
- Enter airflow
- Set one dimension (or aspect ratio)
- Calculate other dimension
- Show equivalent round diameter
Friction Chart
Section titled “Friction Chart”Reading the Chart
Section titled “Reading the Chart”The friction chart shows relationships:
- Airflow vs. duct size vs. velocity vs. friction
- Find any parameter from two known values
Chart Lines
Section titled “Chart Lines”- Velocity lines (diagonal)
- Duct size lines (curved)
- Friction rate (horizontal axis)
- Airflow (vertical axis)
Design Guidelines
Section titled “Design Guidelines”Velocity Limits
Section titled “Velocity Limits”| Application | Max Velocity |
|---|---|
| Main ducts | 2000 FPM |
| Branch ducts | 1200 FPM |
| Noise-sensitive | 800 FPM |
| Residential | 600 FPM |
Friction Limits
Section titled “Friction Limits”| Application | Friction Rate |
|---|---|
| Low velocity | 0.05 in/100 ft |
| Medium velocity | 0.10 in/100 ft |
| High velocity | 0.20 in/100 ft |
Aspect Ratio
Section titled “Aspect Ratio”For rectangular ducts:
- Keep aspect ratio < 4:1
- 1:1 to 2:1 is optimal
- Higher ratios increase friction
Practical Tips
Section titled “Practical Tips”Round vs. Rectangular
Section titled “Round vs. Rectangular”Round ducts have:
- Lower friction for same airflow
- Less material for same capacity
- Better sealing
- May not fit in tight spaces
Equivalent Diameter
Section titled “Equivalent Diameter”Compare rectangular to round:
- Same airflow and friction
- Use for mixed systems
- Verify with friction chart
Real-World Adjustments
Section titled “Real-World Adjustments”Consider:
- Actual available sizes
- Fitting losses
- Installation constraints
- Insulation thickness
Export
Section titled “Export”Results Summary
Section titled “Results Summary”Export sizing results:
- All calculated values
- Design parameters
- Printable format