1. What is the Air Flow Rate 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 professionals, engineers, and technicians calculate air flow rates for ventilation systems, ductwork, and pneumatic applications.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Volumetric flow rate (gallons per minute - GPM)
• \( V \) — Velocity of air (feet per second - ft/s)
• \( A \) — Cross-sectional area (square feet - ft²)
• 448.83 — Conversion factor (accounts for units and standard air density)

Explanation: The formula converts the product of velocity and area from ft³/s to GPM while adjusting for typical air density conditions.

3. Importance of Air Flow Rate Calculation

Details: Accurate flow rate calculations are essential for proper system design, energy efficiency, and ensuring adequate ventilation in buildings and industrial applications.

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 there a conversion factor of 448.83?
A: This factor converts ft³/s to GPM (7.48052) and adjusts for standard air density (60°F at sea level).

Q2: How do I measure air velocity?
A: Use an anemometer or pitot tube to measure velocity at the point of interest in the duct or pipe.

Q3: What's a typical air velocity in HVAC systems?
A: Typically 500-1200 ft/min (8.3-20 ft/s) in main ducts, lower in branch ducts.

Q4: When would I need to adjust the conversion factor?
A: For non-standard temperatures or altitudes, or when working with gases other than air.

Q5: Does this work for liquids too?
A: The basic Q=VA formula works for any fluid, but the conversion factor would need adjustment for liquids.