Prandtl Number

The Prandtl number represents the relationship between the momentum diffusivity, also known as kinematic viscosity, and thermal diffusivity. The Prandtl Number is dimensionless.  The Prandtl Number is only dependent on the fluid and the fluid state, so can be considered a characteristic attribute of various fluids.

Conduction and Convection phenomena essential compete in the transfer of heat and the rates of these two forms of heat transfer varies in different fluids.  The Prandtl Number can be used to estimate which form of heat transfer will outweigh the other.