1. What is the Pressure Drop Equation?

The Hagen-Poiseuille equation calculates pressure drop in laminar flow through a pipe. It's fundamental for designing gas pipelines and understanding fluid dynamics in circular conduits.

2. How Does the Calculator Work?

The calculator uses the Hagen-Poiseuille equation:

Where:

• \( \Delta P \) — Pressure drop (Pa)
• \( \mu \) — Dynamic viscosity (Pa·s)
• \( L \) — Length of pipe (m)
• \( Q \) — Volumetric flow rate (m³/s)
• \( D \) — Inner diameter of pipe (m)

Explanation: The equation shows that pressure drop is directly proportional to viscosity, pipe length, and flow rate, but inversely proportional to the fourth power of pipe diameter.

3. Importance of Pressure Drop Calculation

Details: Accurate pressure drop calculation is crucial for pipeline design, pump selection, and ensuring proper flow rates in gas distribution systems.

4. Using the Calculator

Tips: Enter all values in SI units. Ensure viscosity is in Pa·s, length in meters, flow rate in m³/s, and diameter in meters. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What flow regime does this equation apply to?
A: The Hagen-Poiseuille equation applies only to laminar flow (Re < 2100). For turbulent flow, use the Darcy-Weisbach equation.

Q2: How does pipe roughness affect the calculation?
A: Pipe roughness doesn't affect laminar flow calculations. It only becomes significant in turbulent flow regimes.

Q3: What are typical viscosity values for gases?
A: Air at 20°C has μ ≈ 1.8×10⁻⁵ Pa·s. Natural gas viscosity typically ranges from 1×10⁻⁵ to 1.2×10⁻⁵ Pa·s at standard conditions.

Q4: Can this be used for compressible gases?
A: This form is for incompressible flow. For compressible gases with small pressure drops (<10% of absolute pressure), it can provide approximate results.

Q5: How does temperature affect the calculation?
A: Temperature primarily affects viscosity. Gas viscosity increases with temperature, unlike liquids where it typically decreases.