Dimensionless convective heat transfer coefficient.
Nu=hL/k is the ratio of convective to conductive heat transfer in a fluid layer. Correlations e.g. Dittus-Boelter Nu=0.023Re^{0.8}Pr^{0.4} for turbulent pipe flow. Pr=ν/α compares momentum and thermal diffusion. Laminar pipe flow has Nu≈3.66 (constant wall T).
Water at Re=50 000 and Pr=7 in a 25 mm pipe gives h≈8 kW/m²K.
The Nusselt number is the dimensionless heat transfer coefficient, so it lets you scale convective heat transfer across sizes and fluids.
Dimensionless convective heat transfer coefficient.
The Nusselt number is the dimensionless heat transfer coefficient, so it lets you scale convective heat transfer across sizes and fluids.
The ratio of convective to conductive heat transfer across a boundary layer, so a larger value means better convection.
Correlations give Nusselt number as a function of Reynolds and Prandtl numbers, from which the heat transfer coefficient is found.
Typical applications include correlating heat transfer data for a tube bank in a boiler, comparing convective heat transfer for air and water in a pipe and estimating the convection on a plate using a standard correlation.
Study "Natural and forced convection" first (topic 87 of 105 in Thermodynamics & Fluids). It covers the groundwork this topic builds on.
Stanton number. Colburn j-factor. Use fluid properties at film temperature.
Water at Re=50 000 and Pr=7 in a 25 mm pipe gives h≈8 kW/m²K.
The next topic is "Radiation", which builds directly on this one.
It is classed as Advanced in Thermodynamics & Fluids (topic 88 of 105). It is an advanced topic. It assumes you are comfortable with the intermediate topics in Thermodynamics & Fluids.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.