1. What is an Air Flow Rate Calculator?

Definition: This calculator estimates the volumetric flow rate of air in gallons per minute (GPM) equivalent based on velocity and cross-sectional area.

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:

• \( Q \) — Air flow rate (GPM equivalent)
• \( V \) — Velocity of air (feet per second)
• \( A \) — Cross-sectional area (square feet)
• 448.83 — Conversion factor (ft³/s to GPM)

Explanation: The formula converts the volumetric flow rate from cubic feet per second to gallons per minute.

3. Importance of Air Flow Rate Calculation

Details: Proper air flow rate estimation ensures efficient HVAC system operation, proper ventilation, and energy efficiency.

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 is the result in GPM when calculating air flow?
A: The calculator provides equivalent GPM for comparison with liquid flow rates, though air flow is typically measured in CFM.

Q2: How do I convert the result to CFM?
A: Divide the GPM result by 7.4805 to get cubic feet per minute (CFM).

Q3: What's a typical air velocity in ducts?
A: Residential systems typically range from 500-900 ft/min (8.3-15 ft/s), while commercial systems may go higher.

Q4: How do I measure duct cross-sectional area?
A: For rectangular ducts: width × height. For circular ducts: π × (radius)².

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