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Velocity Pressure Formula:
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Velocity Pressure in Duct 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 represents the energy contained in the moving air within a duct system.
The calculator uses the velocity pressure formula:
Where:
Explanation: The formula calculates the dynamic pressure component in a fluid flow system, which is proportional to the square of the air velocity.
Details: Velocity pressure is crucial for HVAC system design, duct sizing, fan selection, and energy efficiency calculations. It helps determine the total pressure in duct systems and ensures proper air distribution throughout the ventilation system.
Tips: Enter the mean velocity of air in meters per second (m/s). The value must be greater than zero for accurate calculation.
Q1: What is the relationship between velocity and velocity pressure?
A: Velocity pressure is proportional to the square of the air velocity. When velocity doubles, velocity pressure increases by a factor of four.
Q2: How is velocity pressure measured in practice?
A: Velocity pressure is typically measured using a pitot tube connected to a differential pressure gauge, which measures the difference between total pressure and static pressure.
Q3: What are typical velocity pressure values in HVAC systems?
A: Typical values range from 25-250 Pascal depending on the application, with higher values in high-velocity systems and lower values in low-velocity systems.
Q4: How does velocity pressure relate to total pressure?
A: Total pressure equals static pressure plus velocity pressure. This relationship is fundamental to understanding fluid flow in ducts.
Q5: Why is the constant 0.6 used in the formula?
A: The constant 0.6 is derived from the air density (approximately 1.2 kg/m³ at standard conditions) and the conversion factor: P_v = ½ρV², where ρ is air density.