1. What is Supply Air Flow Rate Calculation?

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

Purpose: It helps HVAC professionals and engineers design and evaluate ventilation systems by converting air flow measurements to a standardized unit.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Volumetric flow rate (GPM)
• \( V \) — Air velocity (ft/s)
• \( A \) — Cross-sectional area (ft²)
• 448.83 — Conversion factor (accounts for unit conversion and standard air density)

Explanation: The formula converts air flow from cubic feet per second to gallons per minute while accounting for standard air density conditions.

3. Importance of Air Flow Rate Calculation

Details: Accurate air flow calculations are essential for proper HVAC system design, ensuring adequate ventilation, maintaining indoor air quality, and optimizing energy efficiency.

4. Using the Calculator

Tips: Enter the air velocity in feet per second and the duct cross-sectional area in square feet. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why use GPM for air flow measurement?
A: While CFM is more common for air, GPM equivalent allows comparison with liquid flow rates in systems that handle both.

Q2: What's the significance of the 448.83 factor?
A: It combines unit conversion (1 ft³/s = 448.83 GPM) with standard air density adjustment.

Q3: When would I need this calculation?
A: When designing ventilation systems, balancing air flows, or comparing air and liquid flow rates in combined systems.

Q4: How do I measure air velocity?
A: Use an anemometer at multiple points in the duct and calculate the average velocity.

Q5: Does this account for different air densities?
A: The factor assumes standard air density (0.075 lb/ft³). For significantly different conditions, additional adjustments may be needed.