1. What is the Velocity Pressure to CFM Equation?

The Velocity Pressure to CFM equation calculates airflow in cubic feet per minute from velocity pressure measurements. This is essential for HVAC system design, ventilation analysis, and air flow measurement in various industrial applications.

2. How Does the Calculator Work?

The calculator uses the CFM equation:

Where:

• \( CFM \) — Cubic Feet per Minute (ft³/min)
• \( A \) — Cross-sectional area (ft²)
• \( VP \) — Velocity pressure (in wg)
• \( \rho \) — Air density (lb/ft³)

Explanation: The equation converts velocity pressure to velocity, then multiplies by area to get volumetric flow rate, with unit conversion factors applied.

3. Importance of CFM Calculation

Details: Accurate CFM calculation is crucial for proper ventilation system design, ensuring adequate air exchange rates, maintaining indoor air quality, and optimizing energy efficiency in HVAC systems.

4. Using the Calculator

Tips: Enter cross-sectional area in square feet, velocity pressure in inches water gauge, and air density in pounds per cubic foot. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical air density value?
A: Standard air density at sea level and 70°F is approximately 0.075 lb/ft³, but this varies with altitude and temperature.

Q2: How is velocity pressure measured?
A: Velocity pressure is typically measured using a pitot tube connected to a differential pressure gauge or manometer.

Q3: Why is the 0.3048² factor included?
A: This factor converts from meters to feet squared, as the equation derivation often starts with metric units.

Q4: What are typical CFM values for residential HVAC?
A: Residential systems typically range from 600-2000 CFM depending on the size of the home and system capacity.

Q5: When should air density be measured vs. using standard values?
A: For precise measurements, actual air density should be used. For general applications, standard air density (0.075 lb/ft³) is often acceptable.