1. What is Pressure Drop in Pipe Flow?

Definition: This calculator estimates the pressure drop (ΔP) in a pipe due to viscous flow using the Hagen-Poiseuille equation.

Purpose: It helps engineers and fluid system designers determine the pressure loss in laminar flow conditions.

2. How Does the Calculator Work?

The calculator uses the Hagen-Poiseuille equation:

Where:

• \( \Delta P \) — Pressure drop (Pascals)
• \( \mu \) — Dynamic viscosity (Pa·s)
• \( L \) — Pipe length (meters)
• \( Q \) — Volumetric flow rate (m³/s)
• \( r \) — Pipe radius (meters)

Explanation: The equation describes laminar flow through a cylindrical pipe where viscosity dominates the flow characteristics.

3. Importance of Pressure Drop Calculation

Details: Proper pressure drop estimation ensures adequate pump sizing, system efficiency, and proper fluid delivery in piping systems.

4. Using the Calculator

Tips: Enter the fluid viscosity, pipe length, flow rate, and pipe radius. All values must be > 0. The calculator assumes laminar flow conditions.

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 typically).

Q2: How do I find dynamic viscosity?
A: Check fluid property tables or use a viscometer. Water at 20°C has μ ≈ 0.001 Pa·s.

Q3: Does pipe roughness affect the result?
A: No, this equation assumes smooth pipes. For rough pipes in turbulent flow, use the Darcy-Weisbach equation.

Q4: Why is radius to the 4th power?
A: The strong dependence on radius shows how small diameter changes dramatically affect pressure drop.

Q5: What if my pipe is not circular?
A: This equation is for circular pipes only. For other shapes, use hydraulic diameter methods.