where besides the constant factor K the two other terms are the
volume related power input P/V (W/m3) as well as the superficial
gas velocity wsg (m/s). Note that wsg is directly proportional to the
power input by means of the aeration (compressor) per unit of volume: wsg = (1//g) Paera/V, where is the liquid density and g
the gravitational acceleration.
The fit of this standard correlation to measurement data displayed
in Fig. 5 revealed the parameter set [K; ˛; ˇ] = [1027; 0.74;
0.31].
Although the cultivation experiments were performed with different
configurations of impellers and/or baffles and thus different
power inputs, the cultures could be kept exactly on their desired
optimal paths during the kLa experiments as shown in Fig. 6. This
ensures that the cultivation processes are not significantly influenced
by the kLa measurement procedures.
In order to make sure that the cultivation profiles are not changing
during the kLa experiments, the slope of the aeration rate
modulation function must be restricted to a value at which the pO2
controller is still able to keep the pO2 on track by manipulating
the stirrer speed only. At a constant slope of the triangular modulation
function, the amplitude of the modulation function thus
determines the frequency.