Due to the narrow construction depth and the good axial temperature conductivity, rotor-systems do not freeze tight in central European climates and normal operational conditions.
There is a risk of freezing when employed in countries with outdoor temperatures of below -25 °C.
In case of longer operation at such cold outdoor temperatures a layer of ice can form inside the rotor heat storing mass channels. This ice layer increases the pressure drop on the air side.
Solutions are also available for such operational conditions in order to ensure a fault-free operation of the rotorsystem.
Valid as a rule of thumb under the condition of equal air flow rates:
If tm = (t11+t21) / 2 = 0°C
no freeze problems exists..