1. What is an Air Flow Rate Calculator?

Definition: This calculator determines 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 calculate 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)
• \( V \) — 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 Air Flow Rate Calculation

Details: Accurate air flow calculations ensure proper ventilation, system efficiency, and compliance with design specifications.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: Why convert to GPM instead of CFM?
A: GPM (gallons per minute) equivalent is provided for comparison with liquid flow rates in similar systems.

Q2: What's a typical air velocity in ducts?
A: Typically 600-1200 ft/min (10-20 ft/s) in main ducts, lower 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: Why the 448.83 conversion factor?
A: It converts ft³/s to GPM (1 ft³/s = 448.83 GPM).

Q5: Can I use this for liquid flow too?
A: Yes, but remove the conversion factor (use 1 instead of 448.83) for direct GPM calculation.