1. What is a Flow Rate of Air Calculator?

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

Purpose: It helps engineers and technicians determine air flow rates for HVAC systems, pneumatic systems, and ventilation design.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Flow rate (GPM)
• \( V \) — Velocity (ft/s)
• \( A \) — Cross-sectional area (ft²)
• 448.83 — Conversion factor (ft³/s to GPM)

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

3. Importance of Flow Rate Calculation

Details: Proper flow rate estimation ensures adequate ventilation, proper system sizing, and efficient operation of air-based systems.

4. Using the Calculator

Tips: Enter the velocity in feet per second and cross-sectional area in square feet. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is the result in GPM when calculating air flow?
A: The GPM equivalent allows comparison with liquid flow rates and is commonly used in system specifications.

Q2: What's a typical air velocity in ducts?
A: HVAC systems typically use 800-1200 ft/min (13-20 ft/s) for main ducts and 600-900 ft/min (10-15 ft/s) for branch ducts.

Q3: How do I measure the cross-sectional area?
A: For circular ducts: \( A = \pi r^2 \). For rectangular ducts: \( A = width \times height \).

Q4: What affects air flow rate in a system?
A: Duct size, shape, length, bends, filters, and fan/pump capacity all affect actual flow rates.

Q5: Can I use this for compressed air systems?
A: Yes, but remember compressed air has different properties and may require additional calculations for accurate results.