1. What is Air Flow Through a Pipe?

Definition: This calculator determines the volumetric flow rate of air through a pipe in gallons per minute (GPM) equivalent.

Purpose: It helps HVAC engineers, plumbers, and technicians design and analyze air flow systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

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

Explanation: The velocity is multiplied by the pipe area to get cubic feet per second, then converted to GPM.

3. Importance of Air Flow Calculation

Details: Proper air flow calculation ensures efficient system operation, proper ventilation, and correct equipment sizing.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: Why convert to GPM for air flow?
A: GPM is a common unit for comparing different fluid flows, even when working with air systems.

Q2: How do I find the cross-sectional area?
A: For circular pipes: \( A = \pi \times r^2 \) where r is radius in feet.

Q3: What's a typical air velocity in pipes?
A: HVAC systems typically use 800-1200 ft/min (13.3-20 ft/s) in main ducts.

Q4: Does this work for other gases?
A: Yes, but density differences may require additional adjustments for precise calculations.

Q5: What if I know diameter instead of area?
A: First calculate area from diameter: \( A = \pi \times (D/2)^2 \) where D is diameter in feet.