Air temperature of previous iteration cycle

For cables in troughs and channels, the calculated air temperature inside the enclosed space is damped by taking a mean value of the newly calculated air temperature using the calculated losses within multiplied by a relaxation parameter < 1 and add it to the air temperature of the previous cycle multiplied by 1 minus the relaxation parameter. Initially, this temperature is equal to the ambient air temperature above ground.

Symbol
$\theta_{at_{i}}$
Unit
$^{\circ}$C
Used in
$\theta_{at}$