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Dimensionless quantity calculated as the ratio of momentum diffusivity (kinematic viscosity)  $//<![CDATA[ \begin{array}{l}\nu\end{array} //]]>$ to thermal diffusivity  $//<![CDATA[ \begin{array}{l}a\end{array} //]]>$:

It is dynamic property of the substance at a given pressure and temperature:  $//<![CDATA[ \begin{array}{l}{\rm Pr} = {\rm Pr}(p, T)\end{array} //]]>$.

High values mean that heat convection dominates heat conduction.

For most gases over a wide range of temperature and pressure, Prandtl number is approximately constant at around $//<![CDATA[ \begin{array}{l}{\rm Pr}(p, T) = 0.71\end{array} //]]>$.

For water in STP:   $//<![CDATA[ \begin{array}{l}{\rm Pr} = 7.56\end{array} //]]>$.

See also

Physics / Thermodynamics