What is the Pr (Prandtl Number)?
The Prandtl number compares how fast momentum diffuses versus heat. Pr<1 means heat spreads faster than momentum (thicker thermal layer); Pr>1 the reverse.
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Prandtl Number Calculator
Compute the Prandtl number from specific heat, dynamic viscosity and thermal conductivity to compare momentum and thermal diffusion.
Pr = Cp·μ ÷ k
Frequently asked questions
Can you show a worked example?
Air: Cp=1005, μ=1.81e-5, k=0.0257 → Pr = (1005·1.81e-5)/0.0257 ≈ 0.708 → thermal layer slightly thicker.
How do I read the graph?
The visualisation places your computed Pr against colour-coded regime zones, with a live marker so you can see at a glance which flow or transfer regime your inputs fall into and how close you are to the next threshold.
Where is this used in real life?
Heat-exchanger design, boundary-layer analysis and convective heat-transfer correlations.
What are the limits or edge cases?
All inputs must be physically valid; a zero in the denominator (e.g. zero viscosity, velocity or conductivity) is rejected rather than producing infinity. Regime thresholds are standard textbook values and can shift with geometry and conditions.