Nusselt Number Calculator
Enter heat-transfer coefficient, characteristic length and thermal conductivity to compute the Nusselt number Nu = h·L/k.
Input Data
Results
At a glance:The Nusselt number Nu = h·L/k is a dimensionless measure of convective heat transfer relative to conduction. h is the convective heat-transfer coefficient, L a characteristic length (e.g. tube diameter) and k the fluid's thermal conductivity. Nu = 1 means heat crosses the boundary by pure conduction (stagnant fluid); Nu > 1 means convection enhances transfer. It connects to other dimensionless groups via correlations: forced convection Nu = f(Re, Pr) (Dittus-Boelter), natural convection Nu = f(Gr, Pr). This tool computes Nu = hL/k from h, L, k.
Formula
Nusselt number: Nu = h·L/k
$$\mathrm{Nu} = \dfrac{h\,L}{k}$$How to Use
- Enter the heat-transfer coefficient h (W/(m²·K)).
- Enter the characteristic length L (m) and thermal conductivity k (W/(m·K)).
- The calculator returns Nu.
Case Studies
Pipe flow
h = 500 W/(m²·K), L = 0.05 m, k = 0.6 W/(m·K).
Nu = 500×0.05/0.6 ≈ 41.7.
Strong convection (turbulent, enhanced).
FAQ
What does Nu > 1 tell you?
Convection is active — the effective heat transfer exceeds pure conduction across the same layer, because fluid motion carries energy.
How is Nu used in practice?
Empirical correlations express Nu as a function of Re and Pr (or Gr and Pr), letting you find h for a given geometry and flow, then the heat rate q = h·A·ΔT.
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References
Content review: Calculatorism Editorial Team. Results are for reference only; please refer to the relevant authorities for the official figures.