ASHRAE Terminology

A Comprehensive Glossary of Terms for the Built Environment
ashrae.org/ashraeterms

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Prandtl number

(1) dimensionless number used in calculation of forced and free convection, equal to the dynamic viscosity times the specific heat at constant pressure, divided by the thermal conductivity. (2) dimensionless number used in calculation of diffusion in flowing systems, equal to the kinematic viscosity divided by the molecular diffusivity. Symbol is Pr or Pr. Also known as Schmidt number 1 (Sc, Sc, or NSc1).