Frequency response analysis of continuous flow systems

Abstract The distribution of residence times in a continuous flow system can be deduced from experiments concerning the behaviour of longitudinal concentration gradients on their course through the system. In this paper the application of sinusoidally varying concentrations is treated from a theoretical and experimental viewpoint. As an illustration of this frequency response analysis, experimental results are given for longitudinal diffusion in liquid flow through packed Raschig rings and for back-mixing of a liquid flowing over the packing of an absorption column.