Nusselt number

Summary

The Nusselt number $\mathrm{Nu} = h L / k$ is the dimensionless number that measures how much convection improves heat transfer over pure conduction through a fluid layer. Here $h$ is the heat transfer coefficient and $k$ is the conductivity of the fluid. Results on convection are usually stated as formulas for $\mathrm{Nu}$ in terms of the Reynolds, Prandtl, Grashof or Rayleigh numbers. The Dittus–Boelter equation is one such formula.