1. What is the CFM Equation?

The CFM (Cubic Feet per Minute) equation calculates airflow using pressure and diameter. It provides an accurate assessment of volumetric flow rate in ventilation and HVAC systems.

2. How Does the Calculator Work?

The calculator uses the CFM equation:

Where:

• \( D \) — Diameter (in)
• \( VP \) — Velocity Pressure (in wg)
• \( \rho \) — Density (lb/ft³)

Explanation: The equation calculates airflow by considering the cross-sectional area of the duct and the velocity pressure, adjusted for air density.

3. Importance of CFM Calculation

Details: Accurate CFM calculation is crucial for designing ventilation systems, ensuring proper air exchange rates, and maintaining indoor air quality standards.

4. Using the Calculator

Tips: Enter diameter in inches, velocity pressure in inches water gauge, and density in pounds per cubic foot. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is velocity pressure?
A: Velocity pressure is the pressure caused by air movement in the duct, measured in inches of water gauge (in wg).

Q2: Why is density important in CFM calculation?
A: Air density affects the mass flow rate. Standard air density is 0.075 lb/ft³ at sea level and 70°F.

Q3: What are typical CFM values for ventilation systems?
A: Residential systems typically range from 100-2000 CFM, while commercial systems can range from 2000-20,000 CFM or more.

Q4: How does duct diameter affect CFM?
A: Larger diameter ducts can handle higher CFM values with lower velocity and reduced pressure drop.

Q5: When should this calculation be used?
A: This calculation is essential for HVAC system design, balancing air distribution systems, and troubleshooting airflow problems.