1. What Is Air Flow Rate?

Definition: Air flow rate measures the volume of air moving through a space per unit time, expressed in gallons per minute (GPM) equivalent.

Purpose: This calculation is essential for HVAC system design, ventilation planning, and industrial air movement applications.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Air flow rate (GPM equivalent)
• \( V \) — Velocity of air (feet per second)
• \( A \) — Cross-sectional area (square feet)
• \( 448.83 \) — Conversion factor to GPM

Explanation: The formula converts air velocity through a given area to an equivalent liquid flow rate in gallons per minute.

3. Importance of Air Flow Rate Calculation

Details: Proper air flow calculation ensures adequate ventilation, efficient HVAC operation, and proper equipment sizing for industrial processes.

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 measurement?
A: The GPM equivalent allows comparison with liquid flow rates and standardizes measurements across systems.

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: HVAC systems typically maintain 600-900 ft/min (10-15 ft/s) in main ducts.

Q4: Does this account for air density changes?
A: No, this assumes standard temperature and pressure conditions.

Q5: How do I convert back to CFM?
A: Divide GPM by 448.83 to get ft³/s, then multiply by 60 for CFM.