Convection thermal resistance between surface of cable and air inside the tunnel and in free air.

Symbol
$T_{\mathrm{sa}}$
Unit
K.m/W
Formulae
 $\frac{1}{\left(- \theta_{\mathrm{at}} + \theta_{\mathrm{de}}\right)^{0.25} \left(D_{\mathrm{o}} h_{\mathrm{bs}} \pi - \frac{0.427287006396234}{T_{\mathrm{st}}}\right)}$ in tunnel, Reair ≤ 2000 $\frac{1}{K_{\mathrm{cv}} \mathrm{Re}_{\mathrm{air}}^{0.65} k_{\mathrm{air}} \pi}$ in tunnel, Reair > 2000 $\frac{1}{\left(- \theta_{\mathrm{at_{\mathrm{L}}}} + \theta_{\mathrm{o_{\mathrm{L}}}}\right)^{0.25} \left(D_{\mathrm{o}} h_{\mathrm{bs}} \pi - \frac{0.427287006396234}{T_{\mathrm{st}}}\right)}$ in tunnel, Reair ≤ 2000, IEC 60287-2-3
Related
$D_{\mathrm{o}}$
$h_{\mathrm{bs}}$
$k_{\mathrm{air}}$
$K_{\mathrm{cv}}$
$\pi$
$\mathrm{Re}_{\mathrm{air}}$
$T_{\mathrm{st}}$
$\theta_{\mathrm{at}}$
$\theta_{\mathrm{at_{\mathrm{L}}}}$
$\theta_{\mathrm{de}}$
$\theta_{\mathrm{o_{\mathrm{L}}}}$
Used in
$T_{\mathrm{a}}$
$T_{\mathrm{s}}$
$T_{\mathrm{t}}$
$\theta_{\mathrm{de}}$
$\theta_{\mathrm{hs}}$
$W_{\mathrm{hs}}$
Choices
IdMethodInfo
0CableizerThe method developed by Cableizer is applicable to any type of cable or heat source installed in ventilated tunnels. The method applies to natural as well as forced ventilation. Longitudinal heat transfer in the tunnel air is calculated every meter of tunnel length. Up to four different cable systems, unequally loaded, can be calculated.
1IEC 60287-2-3The method acc. IEC 60287-2-3 is applicable to any type of cable installed in ventilated tunnels. The method applies to natural as well as forced ventilation. Longitudinal heat transfer within the cables and the surroundings of the tunnel is assumed to be negligible. All cables are assumed to be identical and equally loaded within the tunnel.