1. What is a Water Pressure vs Flow Rate Calculator?

Definition: This calculator determines the flow rate of water through a pipe based on the Hagen-Poiseuille equation, which relates pressure difference to laminar flow.

Purpose: It helps engineers, plumbers, and fluid dynamics students understand and predict how pressure affects flow rate in piping systems.

2. How Does the Calculator Work?

The calculator uses the Hagen-Poiseuille equation:

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 equation shows that 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 prediction is essential for designing efficient piping systems, ensuring adequate water supply, and calculating pumping requirements.

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 is the viscosity of water?
A: At 20°C, water has a viscosity of about 0.001002 Pa·s. This changes with temperature.

Q2: Does this work for all fluids?
A: Yes, but only for laminar (not turbulent) flow. For turbulent flow, use the Darcy-Weisbach equation.

Q3: Why does radius have such a big effect?
A: Flow rate depends on the fourth power of radius, so doubling the radius increases flow 16 times.

Q4: What's a typical pressure difference in household plumbing?
A: Typically 100-600 kPa (100,000-600,000 Pa) for municipal water supplies.

Q5: How do I convert flow rate to liters per second?
A: Multiply the m³/s result by 1000 to get liters per second.