Nusselt Number Calculator

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Choose the basic definition to solve for Nu, h, L, or k, or pick a correlation to compute Nu from flow conditions.
Heat flux per unit area per degree of temperature difference at the surface.
W/(m²·K)
For a pipe this is the inner diameter; for a plate it is the plate length.
m
Thermal conductivity of the fluid (e.g. water at 25 °C is about 0.607 W/m·K).
W/(m·K)
Nusselt Number (Nu)Moderate convection
41.667

Ratio of convective to conductive heat transfer

Flow regimeConvection dominated
Convective coefficient (h) from Nu500W/(m²·K)
Correlation validityDirect definition: valid for all convection regimes.
41.667
Conduction dominated<2Weak convection2-10Moderate convection10-100Strong convection100+

Nusselt number is 41.67

  • Nu = 41.7 means convection transfers about 42 times more heat than conduction alone would at the same boundary conditions.

Next stepMultiply Nu by the fluid thermal conductivity k and divide by the characteristic length to recover the convective heat transfer coefficient h = Nu × k / L.

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