1. What is Air Flow CFM?

Definition: CFM (Cubic Feet per Minute) measures the volume of air flow through a space per minute.

Purpose: This calculator helps HVAC professionals, engineers, and technicians determine air flow rates in ventilation systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q_{cfm} \) — Air flow (cubic feet per minute)
• \( V \) — Air velocity (feet per second)
• \( A \) — Cross-sectional area (square feet)
• 60 — Conversion factor (seconds to minutes)

Explanation: The formula converts velocity in ft/s to volume flow in ft³/min by multiplying by the duct area and time conversion.

3. Importance of Air Flow Measurement

Details: Proper air flow calculation ensures adequate ventilation, efficient HVAC system operation, and compliance with building codes.

4. Using the Calculator

Tips: Measure air velocity with an anemometer and duct dimensions to calculate cross-sectional area. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: How do I measure air velocity?
A: Use an anemometer at multiple points in the duct and calculate the average velocity.

Q2: What's a typical air velocity in HVAC ducts?
A: Residential systems typically range from 400-900 FPM (6.7-15 ft/s), while commercial systems may be higher.

Q3: How do I calculate duct cross-sectional area?
A: For rectangular ducts: A = width × height. For circular ducts: A = π × (diameter/2)².

Q4: Why multiply by 60 in the formula?
A: This converts seconds to minutes (60 seconds = 1 minute) to get CFM instead of cubic feet per second.

Q5: How accurate is this calculation?
A: Accuracy depends on precise velocity measurements and accounting for duct shape, bends, and obstructions.