CFM Measurement for Air Flow

Air Flow Formula:

\[ Q_{cfm} = V \times A \times 60 \]

Air Flow (Q_cfm): ft³/min

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1. What is CFM Measurement for Air Flow?

Definition: This calculator measures air flow in Cubic Feet per Minute (CFM) based on velocity and cross-sectional area.

Purpose: It helps HVAC professionals, engineers, and technicians determine the volume of air moving through a duct or space.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ Q_{cfm} = V \times A \times 60 \]

Where:

\( Q_{cfm} \) — Air flow (cubic feet per minute)
\( V \) — Velocity (feet per second)
\( A \) — Cross-sectional area (square feet)

Explanation: The velocity is multiplied by the area to get flow per second, then multiplied by 60 to convert to minutes.

3. Importance of CFM Measurement

Details: Proper air flow measurement ensures efficient HVAC system operation, proper ventilation, and comfort in buildings.

4. Using the Calculator

Tips: Enter the air velocity in feet per second and the cross-sectional area in square feet. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical air velocity in ducts?
A: Residential systems typically range from 400-900 FPM (6.7-15 ft/s), while commercial systems may be higher.

Q2: How do I measure duct area?
A: For rectangular ducts: width × height. For round ducts: π × radius².

Q3: Why multiply by 60 in the formula?
A: This converts from cubic feet per second to cubic feet per minute (60 seconds in a minute).

Q4: What's a good CFM for a room?
A: Generally 1 CFM per square foot of floor area, but this varies by room use and local codes.

Q5: How does CFM relate to air changes?
A: Air changes per hour = (CFM × 60) / room volume in cubic feet.