# Nusselt number, object to gas

Symbol
$\mathrm{Nu}_{og}$
Formulae
 $0.797\left(\mathrm{Gr}_{og} \mathrm{Pr}_{gas}\right)^{0.077} \left(\frac{L_d}{\delta_d}\right)^{-0.052} \left(\frac{D_{di}}{D_o}\right)^{0.505}$ Riser closed at both ends, $Ra < 363 \cdot K^{0.25}G^{0.76}$ (Anders) $0.188\left(\mathrm{Gr}_{og} \mathrm{Pr}_{gas}\right)^{0.322} \left(\frac{L_d}{\delta_d}\right)^{-0.238} \left(\frac{D_{di}}{D_o}\right)^{0.442}$ Riser closed at both ends, $363 \cdot K^{0.25}G^{0.76} < Ra < 2.3 \cdot 10^6$ (Anders) $0.1103\mathrm{Gr}_{og} \mathrm{Pr}_{gas}$ Riser open at both ends, $Gr \cdot Pr < 10$ (Anders) $0.62\left(\mathrm{Gr}_{og} \mathrm{Pr}_{gas}\right)^{0.25}$ Riser open at both ends, otherwise (Anders) $c_{Nu,r} \left(\mathrm{Gr}_{og} \mathrm{Pr}_{gas}\right)^{n_{Nu,r}}$ Riser open at top and closed at bottom (Anders) $c_{Nu,r} \left(\mathrm{Gr}_{og} \mathrm{Pr}_{gas}\right)^{n_{Nu,r}}$ Riser closed at both ends (Hartlein & Black) $0.986{\mathrm{Ra}_{gas}}^{0.177}$ Riser open at both ends, 133 ≤ $Ra$ ≤ 7000 (Hartlein & Black IIa) $c_{Nu,r} \left(\mathrm{Gr}_{og} \mathrm{Pr}_{gas}\right)^{n_{Nu,r}}$ Riser open at both ends, $Ra$ > 7000 (Hartlein & Black IIb) $c_{Nu,r} \left(\mathrm{Gr}_{og} \mathrm{Pr}_{gas}\right)^{n_{Nu,r}}$ Riser open at top and closed at bottom (Hartlein & Black)
Related
$c_{Nu,r}$
$D_{di}$
$D_o$
$\delta_d$
$L_d$
$n_{Nu,r}$
$\mathrm{Pr}_{gas}$
$\mathrm{Ra}_{gas}$
Used in