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Velocity Pressure Formula:
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Velocity pressure is the pressure required to accelerate air from zero velocity to some velocity (V) and is proportional to the kinetic energy of the air stream. It's a critical measurement in HVAC systems for determining airflow in ducts.
The calculator uses the velocity pressure formula:
Where:
Explanation: The formula converts velocity measurements to pressure values that can be used to calculate airflow rates in ventilation systems.
Details: Accurate velocity pressure measurement is essential for proper HVAC system design, balancing airflow in ducts, ensuring adequate ventilation, and maintaining energy efficiency in building systems.
Tips: Enter velocity in feet per minute (fpm). The value must be greater than zero. Typical duct velocities range from 600-2000 fpm depending on application and noise considerations.
Q1: What units are used for velocity pressure?
A: Velocity pressure is typically measured in inches of water gauge (in wg) in the US system or Pascals (Pa) in the metric system.
Q2: Why is the constant 4005 used in the formula?
A: The constant 4005 is derived from standard air density (0.075 lb/ft³) and the relationship between velocity and pressure in air systems.
Q3: How is velocity pressure measured in practice?
A: Velocity pressure is typically measured using a pitot tube connected to a differential pressure gauge, measuring the difference between total pressure and static pressure.
Q4: What are typical velocity pressure values in HVAC systems?
A: Typical values range from 0.01 to 1.0 in wg, depending on the system design and air velocity requirements.
Q5: Can this formula be used for liquids or other gases?
A: No, this specific formula with the 4005 constant is designed for standard air. Different constants would be needed for other fluids based on their density.