Air Flow Pressure Drop Calculator

Pressure Drop Formula:

\[ \Delta P = f \times \left( \frac{L}{D} \right) \times \left( \frac{\rho \times V^2}{2} \right) \]

Friction Factor (f):

dimensionless

Pipe Length (L):

meters

Pipe Diameter (D):

meters

Air Density (ρ):

kg/m³

Flow Velocity (V):

m/s

Pressure Drop (ΔP): Pa

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1. What is an Air Flow Pressure Drop Calculator?

Definition: This calculator estimates the pressure loss in a pipe due to friction using the Darcy-Weisbach equation.

Purpose: It helps engineers and HVAC professionals determine the pressure drop in air duct systems for proper system design.

2. How Does the Calculator Work?

The calculator uses the Darcy-Weisbach equation:

\[ \Delta P = f \times \left( \frac{L}{D} \right) \times \left( \frac{\rho \times V^2}{2} \right) \]

Where:

\( \Delta P \) — Pressure drop (Pascals)
\( f \) — Darcy friction factor (dimensionless)
\( L \) — Pipe length (meters)
\( D \) — Pipe diameter (meters)
\( \rho \) — Air density (kg/m³)
\( V \) — Flow velocity (m/s)

Explanation: The equation calculates the pressure loss due to friction between the moving air and the pipe walls.

3. Importance of Pressure Drop Calculation

Details: Proper pressure drop estimation ensures adequate fan selection, energy efficiency, and proper air distribution in ventilation systems.

4. Using the Calculator

Tips: Enter the friction factor (default 0.02 for smooth pipes), pipe dimensions, air density (default 1.225 kg/m³ at sea level), and flow velocity. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical friction factor value?
A: For smooth pipes, 0.02 is common. Rough pipes may range from 0.03 to 0.05.

Q2: How does pipe diameter affect pressure drop?
A: Pressure drop decreases dramatically with increasing diameter (inverse relationship).

Q3: Why is velocity squared in the equation?
A: Pressure drop is proportional to the kinetic energy of the flow, which depends on velocity squared.

Q4: How does air density affect results?
A: Higher density (cooler air or higher pressure) increases pressure drop proportionally.

Q5: When is this equation not applicable?
A: For very low velocities (laminar flow) or compressible flows at high Mach numbers.