# Outer diameter

Diameter in meters used to calculate the thermal resistance of cables, ducts or heat source in air or for calculations where metric dimension is required.

Symbol
$D_o$
Unit
m
Formulae
 $\frac{D_e}{1000}$ Cables not in duct $\frac{Do_d}{1000}$ Cables in duct $\frac{do_{pipe}}{1000}$ Heat sources $D_{prot}$ PAC/GIL
Related
$D_e$
$D_{prot}$
$Do_d$
$do_{pipe}$
Used in
$A_e$
$A_{er}$
$\alpha_{sa}$
$D_{ext}$
$\delta_d$
$\Delta \theta_{e,t}$
$\Delta \theta_{sun}$
$\mathrm{Gr}_{prot}$
$L_{deep}$
$r_o$
$\mathrm{Re}_{air}$
$T_{4iii}$
$T_{sa}$
$T_{st}$
$W_{conv,od}$
$W_{conv,og}$
$W_{conv,sa}$
$W_{di}$
$W_{rad,od}$
$W_{rad,sa}$
$W_{sun}$