1. What is Volume Flow Rate of Air?

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

Purpose: It helps HVAC engineers, mechanical designers, and technicians calculate air flow rates for system design and analysis.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

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

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

3. Importance of Air Flow Rate Calculation

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

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: Why convert to GPM when measuring air?
A: GPM equivalents are often used for comparison with liquid systems or when integrating air and liquid systems.

Q2: What's a typical air velocity in ducts?
A: Typically 600-900 ft/min (10-15 ft/s) for main ducts, 400-600 ft/min (6.7-10 ft/s) for branch ducts.

Q3: How do I measure cross-sectional area?
A: For round ducts: A = π × (diameter/2)². For rectangular ducts: A = width × height.

Q4: What affects the conversion factor?
A: The factor 448.83 comes from 60 sec/min × 7.4805 gallons/ft³ (water at 60°F).

Q5: Does this account for air density changes?
A: No, this is a volumetric flow calculation. For mass flow, you'd need to include air density.