Duct Air Velocity Calculator

Air Velocity Equation:

\[ v = \frac{CFM \times 60}{A} \]

Air Velocity (v):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Duct Air Velocity?

Duct air velocity refers to the speed at which air moves through a duct system. It is a critical parameter in HVAC design that affects system efficiency, noise levels, and air distribution throughout a building.

2. How Does the Calculator Work?

The calculator uses the air velocity equation:

\[ v = \frac{CFM \times 60}{A} \]

Where:

\( v \) — Air velocity (feet per minute)
\( CFM \) — Airflow rate (cubic feet per minute)
\( A \) — Cross-sectional area of duct (square feet)
\( 60 \) — Conversion factor (minutes to seconds)

Explanation: This equation calculates the linear velocity of air by dividing the volumetric flow rate by the cross-sectional area through which the air is flowing.

3. Importance of Air Velocity Calculation

Details: Proper air velocity is essential for efficient HVAC system operation. Too high velocity causes excessive noise and pressure drop, while too low velocity can lead to poor air distribution and potential duct contamination.

4. Using the Calculator

Tips: Enter CFM in cubic feet per minute and cross-sectional area in square feet. Both values must be positive numbers greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the recommended air velocity for residential ducts?
A: Typically 600-900 fpm for main ducts and 400-600 fpm for branch ducts, depending on the application and noise considerations.

Q2: How do I calculate duct cross-sectional area?
A: For rectangular ducts: A = width × height. For round ducts: A = π × (diameter/2)².

Q3: What happens if air velocity is too high?
A: High velocity increases noise levels, static pressure, and energy consumption while potentially causing air turbulence and vibration.

Q4: What are typical CFM requirements for different rooms?
A: Bedrooms: 50-100 CFM, Living rooms: 100-150 CFM, Kitchens: 100-150 CFM, Bathrooms: 50-100 CFM (varies by size and usage).

Q5: Can this calculator be used for metric units?
A: This calculator uses imperial units. For metric, convert CFM to m³/s and area to m², then use v = flow rate / area in m/s.