Temperature of outer tunnel wall at z

Symbol
$\theta_{to_{z}}$
Unit
$^{\circ}$C
Formulae
$\theta_{t_{z}} + \frac{T_{tw} \left(\theta_{a} - \theta_{t_{z}}\right)}{T_{e}}$
$\theta_{a}$
Ambient temperature [$^{\circ}$C]
$\theta_{t_{z}}$