Pressure Water Pipe Flow Calculator

Flow Rate Formula:

\[ Q = \frac{\pi \times r^4 \times \Delta P}{8 \times \mu \times L} \]

Pipe Radius:

meters

Pressure Difference:

Pascals (Pa)

Fluid Viscosity:

Pa·s

Pipe Length:

meters

Flow Rate (m³/s):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is a Pressure Water Pipe Flow Calculator?

Definition: This calculator estimates the volumetric flow rate in a pipe using the Hagen-Poiseuille equation for laminar flow.

Purpose: It helps engineers, plumbers, and fluid system designers determine flow rates in pipes based on pressure differences and pipe characteristics.

2. How Does the Calculator Work?

The calculator uses the Hagen-Poiseuille equation:

\[ Q = \frac{\pi \times r^4 \times \Delta P}{8 \times \mu \times L} \]

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 is directly proportional to the pressure difference and the fourth power of the radius, and inversely proportional to viscosity and pipe length.

3. Importance of Flow Rate Calculation

Details: Accurate flow rate estimation ensures proper system design, adequate pressure maintenance, and efficient fluid transport in plumbing, HVAC, and industrial systems.

4. Using the Calculator

Tips: Enter pipe radius in meters, pressure difference in Pascals, fluid viscosity (default 0.001002 Pa·s for water at 20°C), and pipe length in meters. 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 fourth power?
A: Flow rate is extremely sensitive to pipe diameter because both the cross-sectional area and velocity profile depend on radius.

Q3: What's the typical viscosity of water?
A: Water at 20°C has viscosity of ~0.001002 Pa·s. Viscosity decreases with temperature.

Q4: How does pipe length affect flow?
A: Longer pipes have greater friction losses, reducing flow rate for a given pressure difference.

Q5: Can I use this for gases?
A: Only for very slow gas flows. Gases are compressible and typically require different equations.