1. What is an Air Velocity to Flow Rate Calculator?

Definition: This calculator converts air velocity and cross-sectional area into an equivalent flow rate in gallons per minute (GPM).

Purpose: It helps HVAC professionals, engineers, and technicians determine air flow rates for system design and analysis.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Flow rate (gallons per minute, GPM)
• \( V \) — Air velocity (feet per second, ft/s)
• \( A \) — Cross-sectional area (square feet, ft²)
• \( 448.83 \) — Conversion factor (ft³/s to GPM)

Explanation: The formula converts the volumetric air flow (velocity × area) from cubic feet per second to gallons per minute.

3. Importance of Flow Rate Calculation

Details: Accurate flow rate calculations are essential for proper HVAC system design, duct sizing, and ensuring adequate ventilation.

4. Using the Calculator

Tips: Enter the air velocity in ft/s and the cross-sectional area in ft². All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why use GPM for air flow?
A: While CFM is more common for air, this conversion allows comparison with liquid flow rates in systems that handle both.

Q2: How do I measure air velocity?
A: Use an anemometer at multiple points in the duct and calculate the average velocity.

Q3: What's a typical air velocity in ducts?
A: Residential systems typically range from 400-900 ft/min (6.67-15 ft/s), while commercial systems may go higher.

Q4: How do I calculate cross-sectional area?
A: For round ducts: \( A = \pi \times r^2 \). For rectangular ducts: \( A = width \times height \).

Q5: Why 448.83 as the conversion factor?
A: It converts cubic feet per second to gallons per minute (1 ft³/s = 448.83 GPM).