The Prandtl number compares momentum diffusivity with thermal diffusivity.
Difficulty
Intermediate
Read time
4 min
Prerequisites
Consistent SI units, algebra, and the physical assumptions listed below
Source
Teng-Jui Lin — Equation SheetsAdapted from Teng-Jui Lin, Equation Sheets — Mechanical Engineering, under CC BY 4.0.
Adapted notation and added original explanations, variables, assumptions, applications, and a worked example.
The Prandtl number compares momentum diffusivity with thermal diffusivity. It helps determine whether velocity and thermal boundary layers grow on similar scales; it does not by itself give a heat-transfer coefficient.
| Symbol | Meaning | Units |
|---|---|---|
| Prandtl number | ||
| Kinematic viscosity | ||
| Thermal diffusivity |
Supply the fluid-property group in a Nusselt correlation.
Compare momentum and thermal diffusion scales.
A fluid has ν = 1.5 × 10⁻⁵ m²/s and α = 2.1 × 10⁻⁵ m²/s. Find Pr.
Adapted from Teng-Jui Lin, Equation Sheets — Mechanical Engineering, under CC BY 4.0.
Adapted notation and added original explanations, variables, assumptions, applications, and a worked example.
Assumptions
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