1. What is an Air Flow Formula Calculator?

Definition: This calculator estimates the volumetric flow rate of air based on velocity and cross-sectional area.

Purpose: It helps HVAC professionals, engineers, and technicians determine air flow rates in ducts, pipes, and ventilation systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Volumetric flow rate (gallons per minute, GPM)
• \( V \) — Velocity of air (feet per second, ft/s)
• \( A \) — Cross-sectional area (square feet, ft²)
• \( 448.83 \) — Conversion factor (ft³/s to GPM)

Explanation: The velocity is multiplied by the area to get flow in ft³/s, then converted to GPM.

3. Importance of Air Flow Calculation

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

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: Why is the conversion factor 448.83?
A: This converts cubic feet per second to gallons per minute (1 ft³/s = 448.83 GPM).

Q2: What's a typical air velocity in HVAC systems?
A: Typically 700-900 ft/min (11.7-15 ft/s) in main ducts, 500-700 ft/min in branch ducts.

Q3: How do I measure duct area?
A: For round ducts: \( A = \pi r^2 \). For rectangular ducts: \( A = width \times height \).

Q4: Can I use this for liquid flow?
A: Yes, the same formula applies to any fluid when using consistent units.

Q5: How accurate is this calculation?
A: It provides theoretical flow; actual flow may vary due to friction, turbulence, and other factors.