Duct Friction Loss Calculator

Darcy-Weisbach Equation:

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

Friction Factor (f):

Length (L):

Diameter (D):

Density (ρ):

kg/m³

Velocity (V):

m/s

Pressure Loss (ΔP):

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1. What is the Darcy-Weisbach Equation?

The Darcy-Weisbach equation is a fundamental equation in fluid mechanics used to calculate the pressure loss due to friction along a given length of duct or pipe. It provides a more accurate assessment of friction losses in duct systems compared to simpler empirical equations.

2. How Does the Calculator Work?

The calculator uses the Darcy-Weisbach equation:

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

Where:

\( \Delta P \) — Pressure loss (Pa)
\( f \) — Friction factor (dimensionless)
\( L \) — Length of duct (m)
\( D \) — Diameter of duct (m)
\( \rho \) — Fluid density (kg/m³)
\( V \) — Fluid velocity (m/s)

Explanation: The equation accounts for the energy loss due to friction between the fluid and the duct walls, with the friction factor depending on the Reynolds number and relative roughness of the duct surface.

3. Importance of Pressure Loss Calculation

Details: Accurate pressure loss calculation is crucial for designing efficient duct systems, selecting appropriate fan or pump sizes, and ensuring proper airflow in HVAC systems and industrial applications.

4. Using the Calculator

Tips: Enter friction factor (typically 0.01-0.05 for smooth ducts), duct length and diameter in meters, fluid density in kg/m³, and fluid velocity in m/s. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: How do I determine the friction factor?
A: The friction factor depends on Reynolds number and relative roughness. For smooth ducts, typical values range from 0.01 to 0.05. More precise values can be obtained from Moody charts or Colebrook equation.

Q2: What are typical pressure loss values in duct systems?
A: Typical values range from 0.5 to 5 Pa per meter of duct length, depending on duct size, airflow velocity, and surface roughness.

Q3: Does this equation work for both liquids and gases?
A: Yes, the Darcy-Weisbach equation is applicable to both liquids and gases, as long as the appropriate density value is used.

Q4: Are there limitations to this equation?
A: The equation assumes fully developed turbulent flow and may need adjustments for very low Reynolds numbers (laminar flow) or extremely rough surfaces.

Q5: How does duct shape affect the calculation?
A: For non-circular ducts, use the hydraulic diameter (4 × cross-sectional area / perimeter) instead of the diameter D in the equation.