1. What is the Air Flow Rate Equation?

Definition: This calculator computes 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 determine air flow rates in ducts and piping systems.

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 is multiplied by the area to get flow in ft³/s, then converted to GPM.

3. Importance of Air Flow Rate Calculation

Details: Proper air flow calculation ensures efficient HVAC system design, proper ventilation, and energy efficiency in air handling systems.

4. Using the Calculator

Tips: Enter the air velocity in ft/s and the 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: What's a typical air velocity in ducts?
A: For HVAC systems, typical velocities range from 500-2000 ft/min (8.33-33.33 ft/s).

Q3: How do I measure duct area?
A: For round ducts: A = π × r² (r = radius in feet). For rectangular ducts: A = width × height (in feet).

Q4: Can this be used for liquids?
A: Yes, the same formula applies to any fluid when using consistent units.

Q5: How does temperature affect the calculation?
A: Temperature affects air density but not the volumetric flow rate calculation shown here.