Nusselt number, duct to air

The equation for forced convection is the well-known Grimson correlation as published in the paper 'Correlation and Utilization of New Data on Flow Resistance and Heat Transfer for Cross Flow of Gases over Tube Banks' by E.D. Grimson, 1937.

Symbol
$\mathrm{Nu}_{ext}$
Formulae
$c_{Nu,r} \left(\mathrm{Gr}_{ext} \mathrm{Pr}_{gas}\right)^{n_{Nu,r}}$natural convection
$s_{Nu,r} {\mathrm{Re}_{air}}^{p_{Nu,r}} {\mathrm{Pr}_{gas}}^{0.333}$forced convection
Related
$c_{Nu,r}$
$\mathrm{Gr}_{ext}$
$n_{Nu,r}$
$p_{Nu,r}$
$\mathrm{Pr}_{gas}$
$\mathrm{Re}_{air}$
$s_{Nu,r}$
Used in