Reynolds Number Calculator Pipe

Reynolds Number Equation for Pipe Flow:

\[ Re = \frac{\rho \cdot v \cdot D}{\mu} \]

Fluid Density (ρ):

kg/m³

Flow Velocity (v):

m/s

Pipe Diameter (D):

Dynamic Viscosity (μ):

Pa·s

Reynolds Number (Re):

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1. What is Reynolds Number for Pipe Flow?

The Reynolds number (Re) is a dimensionless quantity used to predict flow patterns in fluid dynamics. For pipe flow, it helps determine whether the flow is laminar, transitional, or turbulent.

2. How Does the Calculator Work?

The calculator uses the Reynolds number equation for pipe flow:

\[ Re = \frac{\rho \cdot v \cdot D}{\mu} \]

Where:

\( Re \) — Reynolds number (dimensionless)
\( \rho \) — Fluid density (kg/m³)
\( v \) — Flow velocity (m/s)
\( D \) — Pipe diameter (m)
\( \mu \) — Dynamic viscosity (Pa·s)

Explanation: The Reynolds number represents the ratio of inertial forces to viscous forces in the fluid flow.

3. Importance of Reynolds Number

Details: The Reynolds number is crucial for:

Determining flow regime (laminar, transitional, or turbulent)
Designing piping systems
Calculating friction factors
Predicting heat transfer rates
Modeling fluid behavior in various engineering applications

4. Using the Calculator

Tips:

Enter all values in the specified units
For water at 20°C: ρ ≈ 998 kg/m³, μ ≈ 0.001002 Pa·s
For air at 20°C: ρ ≈ 1.204 kg/m³, μ ≈ 0.0000181 Pa·s
All input values must be positive numbers

5. Frequently Asked Questions (FAQ)

Q1: What do different Reynolds number ranges indicate?
A: Typically: Re < 2300 (laminar), 2300 < Re < 4000 (transitional), Re > 4000 (turbulent). These thresholds can vary based on system geometry.

Q2: Why is Reynolds number dimensionless?
A: The units in the numerator and denominator cancel out, making it a pure number without dimensions.

Q3: Can this calculator be used for non-circular pipes?
A: For non-circular conduits, use the hydraulic diameter (4 × area/perimeter) instead of pipe diameter.

Q4: What's the difference between dynamic and kinematic viscosity?
A: Kinematic viscosity (ν) is dynamic viscosity (μ) divided by density (ρ). The Reynolds number can also be expressed as Re = vD/ν.

Q5: How does temperature affect Reynolds number?
A: Temperature changes affect viscosity and density, which in turn affect Re. For liquids, viscosity typically decreases with temperature, while for gases it increases.