Pressure Drop in Tube Calculator

Pressure Drop Formula (Hagen-Poiseuille):

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

Viscosity (μ):

Pa·s

Tube Length (L):

Flow Rate (Q):

m³/s

Tube Radius (r):

Pressure Drop (ΔP):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Pressure Drop in Tube Calculator?

Definition: This calculator determines the pressure drop in a tube for laminar flow using the Hagen-Poiseuille equation.

Purpose: It helps engineers and fluid dynamics professionals analyze pressure losses in piping systems.

2. How Does the Calculator Work?

The calculator uses the Hagen-Poiseuille equation:

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

Where:

\( \Delta P \) — Pressure drop (Pascals)
\( \mu \) — Dynamic viscosity (Pa·s)
\( L \) — Length of the tube (meters)
\( Q \) — Volumetric flow rate (m³/s)
\( r \) — Inner radius of the tube (meters)

Explanation: The equation describes laminar flow through a cylindrical pipe where viscosity dominates over inertia.

3. Importance of Pressure Drop Calculation

Details: Accurate pressure drop calculations are essential for designing efficient piping systems, selecting appropriate pumps, and ensuring proper fluid flow.

4. Using the Calculator

Tips: Enter the fluid viscosity, tube length, flow rate, and tube radius. All values must be > 0. The radius has a strong effect (r⁴ relationship).

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 does tube diameter affect pressure drop?
A: Pressure drop is inversely proportional to the fourth power of the radius, so small diameter changes have large effects.

Q3: What are typical viscosity values?
A: Water at 20°C has μ ≈ 0.001 Pa·s, while honey might be 2-10 Pa·s.

Q4: Can I use this for gases?
A: Only for very slow gas flows where compressibility effects are negligible.

Q5: What if my flow is turbulent?
A: You would need to use the Darcy-Weisbach equation with friction factors instead.