Velocity Pressure To CFM Calculator For Pipe

CFM Formula:

\[ CFM = \pi r^2 \times \sqrt{\frac{2 \times VP}{\rho}} \times 60 \]

CFM (ft³/min):

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1. What is the Velocity Pressure to CFM Equation?

The Velocity Pressure to CFM equation calculates the cubic feet per minute (CFM) of air flow in a pipe based on the velocity pressure, pipe radius, and air density. This is essential for HVAC system design and air flow analysis.

2. How Does the Calculator Work?

The calculator uses the CFM equation:

\[ CFM = \pi r^2 \times \sqrt{\frac{2 \times VP}{\rho}} \times 60 \]

Where:

\( r \) — Radius of the pipe (ft)
\( VP \) — Velocity pressure (in wg)
\( \rho \) — Air density (lb/ft³)
\( \pi \) — Mathematical constant pi (approximately 3.1416)

Explanation: The equation calculates the volumetric flow rate by combining the cross-sectional area of the pipe with the velocity derived from velocity pressure and air density.

3. Importance of CFM Calculation

Details: Accurate CFM calculation is crucial for proper HVAC system design, ventilation requirements, air balancing, and ensuring adequate air flow for various industrial and commercial applications.

4. Using the Calculator

Tips: Enter pipe radius in 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 velocity pressure?
A: Velocity pressure is the pressure caused by air in motion, measured as the difference between total pressure and static pressure in a duct system.

Q2: 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, temperature, and humidity.

Q3: Why is the radius squared in the formula?
A: The radius is squared to calculate the cross-sectional area of the pipe (πr²), which is multiplied by velocity to determine volumetric flow rate.

Q4: When should this calculation be used?
A: This calculation is used in HVAC design, industrial ventilation, duct system analysis, and any application requiring air flow measurement in pipes or ducts.

Q5: Are there limitations to this equation?
A: The equation assumes uniform flow distribution, incompressible flow, and may have reduced accuracy in non-circular ducts or with turbulent flow conditions.