Velocity Pressure To CFM Calculator Formula

CFM Formula:

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

CFM (Cubic Feet per Minute):

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1. What is the Velocity Pressure to CFM Formula?

The Velocity Pressure to CFM formula calculates the airflow rate (Cubic Feet per Minute) based on the cross-sectional area and velocity pressure measurement. This is commonly used in HVAC systems and airflow measurement applications.

2. How Does the Calculator Work?

The calculator uses the CFM formula:

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

Where:

\( CFM \) — Cubic Feet per Minute (ft³/min)
\( A \) — Cross-sectional area (ft²)
\( VP \) — Velocity pressure (in wg)
4005 — Conversion constant

Explanation: The formula converts velocity pressure measurements into actual airflow volume, 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, ventilation assessment, airflow balancing, and ensuring adequate air exchange rates in various applications.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is velocity pressure?
A: Velocity pressure is the pressure created by air movement, measured as the difference between total pressure and static pressure in a duct system.

Q2: Why is the constant 4005 used?
A: The constant 4005 incorporates conversion factors for units (inches water gauge to feet per minute) and accounts for standard air density conditions.

Q3: What are typical CFM values for different applications?
A: CFM requirements vary widely - residential HVAC systems typically range from 400-2000 CFM, while commercial systems can exceed 10,000 CFM depending on building size and usage.

Q4: When should this calculation be used?
A: This calculation is used when you have velocity pressure measurements from a pitot tube or other pressure measurement devices in ductwork.

Q5: Are there limitations to this formula?
A: This formula assumes standard air density (0.075 lb/ft³) and may need adjustment for non-standard temperature, pressure, or humidity conditions.