# Prandtl Number

A dimensionless group often used in heat exchange calculations, relating the ratio of a fluid′s capacity to diffuse momentum to its capacity to diffuse heat.

*where**P*= Prandtl Number*C*= specific heat capacity [Jkg_{p}^{-1}K^{-1}]*η*= dynamic viscosity [kgm^{-1}s^{-1}]*λ*= thermal conductivity [Wm^{-1}K^{-1}]

The Prandtl number may also be defined as the product of the Reynolds and Peclet numbers.

**See also: **Grashof Number, Heat, Peclet Number, Reynolds Number.

**Subjects: ** Mechanical Engineering Physics