1. What is the Air Flow Calculation Formula?

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

Purpose: It helps HVAC engineers, mechanical designers, and technicians calculate air flow rates for ventilation systems and ductwork.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

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

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

3. Importance of Air Flow Calculation

Details: Accurate air flow calculations ensure proper ventilation, efficient system design, and compliance with building codes.

4. Using the Calculator

Tips: Enter the air velocity in ft/s and the duct 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 provides a standardized unit that's comparable to liquid flow rates in many systems.

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.

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

Q4: Does this account for air density changes?
A: No, this assumes standard temperature and pressure conditions.

Q5: What's the 448.83 conversion factor?
A: It converts cubic feet per second to gallons per minute (1 ft³/s = 448.83 GPM).