Velocity Pressure To CFM Calculator Conversion

CFM Equation:

\[ CFM = 4005 \times A \times \sqrt{VP} \]

CFM (Cubic Feet per Minute):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Velocity Pressure to CFM Conversion?

The Velocity Pressure to CFM conversion calculates airflow rate in cubic feet per minute (CFM) using the duct area and velocity pressure measurement. This is a fundamental calculation in HVAC system design and analysis.

2. How Does the Calculator Work?

The calculator uses the CFM equation:

\[ CFM = 4005 \times A \times \sqrt{VP} \]

Where:

\( CFM \) — Airflow rate in cubic feet per minute
\( A \) — Cross-sectional area of the duct in square feet
\( VP \) — Velocity pressure in inches of water gauge
4005 — Conversion constant

Explanation: The equation converts velocity pressure measurements to actual airflow rates, accounting for the relationship between pressure and velocity in fluid dynamics.

3. Importance of CFM Calculation

Details: Accurate CFM calculation is essential for proper HVAC system design, balancing airflow in ventilation systems, ensuring adequate air exchange rates, and maintaining indoor air quality standards.

4. Using the Calculator

Tips: Enter the duct cross-sectional area in square feet and velocity pressure in inches of water gauge. Both values must be positive numbers greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

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

Q2: Why is the constant 4005 used?
A: The constant 4005 incorporates conversion factors for units and accounts for standard air density at 70°F and 29.92 inches of mercury.

Q3: When should this calculation be used?
A: This calculation is used when designing ventilation systems, balancing air flows, troubleshooting HVAC performance, and verifying system compliance with design specifications.

Q4: Are there limitations to this equation?
A: The equation assumes standard air density. Corrections may be needed for high altitudes, extreme temperatures, or non-standard air compositions.

Q5: How is velocity pressure measured?
A: Velocity pressure is typically measured using a pitot tube connected to a differential pressure gauge, with measurements taken at multiple points across the duct for accuracy.