How To Calculate Air Velocity From Pressure And Diameter

Air Velocity Equation:

\[ V = \sqrt{\frac{2 \Delta P}{\rho}} \]

Air Velocity (V):

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1. What Is The Air Velocity Equation?

The air velocity equation calculates the speed of air flow based on pressure drop and air density. This fundamental equation is derived from Bernoulli's principle and is widely used in fluid dynamics and HVAC applications.

2. How Does The Calculator Work?

The calculator uses the air velocity equation:

\[ V = \sqrt{\frac{2 \Delta P}{\rho}} \]

Where:

\( V \) — Air velocity (m/s)
\( \Delta P \) — Pressure drop (Pa)
\( \rho \) — Air density (kg/m³)

Explanation: The equation shows that air velocity is proportional to the square root of the pressure drop and inversely proportional to the square root of air density.

3. Importance Of Air Velocity Calculation

Details: Accurate air velocity calculation is essential for designing ventilation systems, calculating airflow rates, determining pressure losses, and optimizing energy efficiency in HVAC systems.

4. Using The Calculator

Tips: Enter pressure drop in Pascals (Pa) and air density in kg/m³. Both values must be positive numbers. Standard air density at sea level and 20°C is approximately 1.2 kg/m³.

5. Frequently Asked Questions (FAQ)

Q1: What is the relationship between pressure drop and velocity?
A: Velocity increases with the square root of pressure drop. Doubling the pressure drop increases velocity by approximately 41%.

Q2: How does air density affect velocity?
A: Higher air density results in lower velocity for the same pressure drop. Cold air (higher density) moves slower than warm air at the same pressure differential.

Q3: What are typical air velocity values in ventilation systems?
A: Typical values range from 2-5 m/s in residential systems to 5-10 m/s in commercial systems, depending on application and noise considerations.

Q4: Are there limitations to this equation?
A: This equation assumes incompressible flow and neglects friction losses. It's most accurate for short duct runs and moderate pressure drops.

Q5: How does duct diameter affect air velocity?
A: For a constant flow rate, velocity is inversely proportional to the square of the diameter. Halving the diameter quadruples the velocity.