Fan Air Flow Calculation Formula

Fan Air Flow Formula:

\[ CFM = RPM \times A \times VF \]

CFM (Cubic Feet per Minute):

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1. What is Fan Air Flow Calculation?

Fan Air Flow Calculation estimates the volume of air moved by a fan per minute, measured in CFM (Cubic Feet per Minute). This calculation is essential for HVAC system design, ventilation planning, and fan performance evaluation.

2. How Does the Calculator Work?

The calculator uses the fan airflow formula:

\[ CFM = RPM \times A \times VF \]

Where:

\( CFM \) — Cubic Feet per Minute (airflow rate)
\( RPM \) — Fan revolutions per minute
\( A \) — Blade area in square feet
\( VF \) — Velocity factor (dimensionless)

Explanation: The formula calculates airflow by multiplying fan speed (RPM) with the blade area and adjusting for the velocity factor which accounts for blade design and efficiency.

3. Importance of CFM Calculation

Details: Accurate CFM calculation is crucial for proper ventilation system design, energy efficiency optimization, and ensuring adequate air circulation in residential, commercial, and industrial spaces.

4. Using the Calculator

Tips: Enter fan RPM (revolutions per minute), blade area in square feet, and velocity factor (typically between 0.3-0.7 depending on blade design). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical velocity factor range?
A: Velocity factor typically ranges from 0.3 to 0.7, depending on blade design, pitch angle, and fan efficiency.

Q2: How do I measure blade area?
A: Blade area is calculated as the total swept area of the fan blades. For circular fans, use π × (blade radius)² and convert to square feet.

Q3: What are typical CFM values for residential fans?
A: Bathroom fans: 50-110 CFM, Kitchen range hoods: 100-400 CFM, Whole-house fans: 1000-7000 CFM depending on home size.

Q4: Does blade pitch affect the calculation?
A: Yes, blade pitch affects the velocity factor. Steeper pitches generally have higher velocity factors and move more air at the same RPM.

Q5: How accurate is this calculation method?
A: This provides a good estimate for standard applications. For precise engineering applications, consider fan performance curves and manufacturer specifications.