1. What is the Air Flow Measurement Formula?

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

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

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

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

Explanation: The velocity and area are multiplied to get cubic feet per second, then converted to GPM.

3. Importance of Air Flow Measurement

Details: Accurate air flow calculations are essential for proper HVAC system design, ventilation requirements, and energy efficiency.

4. Using the Calculator

Tips: Enter the velocity in ft/s and cross-sectional area in ft². All 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: How do I measure velocity in a duct?
A: Use an anemometer or pitot tube to measure air velocity at multiple points.

Q3: What's a typical air velocity in HVAC systems?
A: Typically 500-1200 ft/min (8-20 ft/s) in main ducts, lower in branch ducts.

Q4: How do I calculate duct cross-sectional area?
A: For round ducts: A = π × r². For rectangular ducts: A = width × height.

Q5: Does this work for liquids too?
A: Yes, the same formula applies to liquid flow in pipes when using consistent units.