1. What is Pipe Flow Rate Calculator?

Definition: This calculator determines the volumetric flow rate of water through a pipe under pressure using the Hagen-Poiseuille equation.

Purpose: It helps engineers and plumbers design and analyze laminar flow systems in pipes.

2. How Does the Calculator Work?

The calculator uses the Hagen-Poiseuille formula:

Where:

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

Explanation: The flow rate increases with larger radius and pressure difference, but decreases with higher viscosity and longer pipes.

3. Importance of Flow Rate Calculation

Details: Accurate flow rate prediction ensures proper system design, adequate water supply, and efficient energy use in piping systems.

4. Using the Calculator

Tips: Enter pipe radius (0.01m for 2cm diameter), pressure difference (1000-100000 Pa typical), viscosity (0.001002 Pa·s for water at 20°C), and pipe length. All values must be > 0.

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 < 2000). For turbulent flow, use the Darcy-Weisbach equation.

Q2: Why is radius to the 4th power so important?
A: The r⁴ relationship means small diameter changes dramatically affect flow rate. Doubling radius increases flow 16x.

Q3: What's the default viscosity value?
A: 0.001002 Pa·s is the dynamic viscosity of water at 20°C (68°F).

Q4: How does temperature affect the calculation?
A: Higher temperatures decrease water viscosity (e.g., 0.000890 Pa·s at 25°C), increasing flow rate for same pressure.

Q5: What are typical pressure differences in residential systems?
A: Household water pressure is typically 200,000-500,000 Pa (2-5 bar), but pressure drops across pipes are usually much smaller.