1. What is Fan CFM?

CFM (Cubic Feet per Minute) is a measurement of airflow volume, indicating how much air a fan can move per minute. It's a crucial parameter for HVAC system design and fan selection.

2. How Does the Calculator Work?

The calculator uses the fan CFM equation:

Where:

• \( RPM \) — Fan revolutions per minute
• \( impeller\_dia \) — Diameter of the fan impeller in inches
• \( efficiency \) — Fan efficiency (typically 0.7-0.9)
• \( constant \) — Conversion constant (typically 3456 for standard conditions)

Explanation: The equation accounts for the relationship between fan speed, impeller size, and efficiency to determine airflow volume.

3. Importance of CFM Calculation

Details: Accurate CFM calculation is essential for proper ventilation system design, ensuring adequate air exchange rates and energy efficiency.

4. Using the Calculator

Tips: Enter RPM, impeller diameter in inches, efficiency (0-1 range), and appropriate constant. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a good CFM for a room fan?
A: For residential use, 100-200 CFM is common for small rooms, while larger spaces may need 300-500 CFM or more.

Q2: How does impeller diameter affect CFM?
A: CFM increases with the cube of impeller diameter, so small increases in diameter result in large CFM gains.

Q3: What's a typical fan efficiency value?
A: Most fans have 70-90% efficiency (0.7-0.9), with high-quality industrial fans reaching up to 0.93.

Q4: Why is the constant 3456?
A: This accounts for unit conversions and standard air density (0.075 lb/ft³) at sea level and 70°F.

Q5: How accurate is this calculation?
A: It provides a good estimate but actual CFM may vary due to ductwork, static pressure, and other system factors.