Low-Cost Experiments in Mass Transfer: Part 4. Measuring Axial Dispersion in a Bubble Column
Axial dispersion affects continuous mass transfer processes because it causes deviations from ideal plug flow. In this experiment involving an 8.9-cm diameter bubble column, axial dispersion is observed when an acid tracer is added at the top of the column, which initially contains a weakly alkaline solution; the fast acid-base reaction is controlled by mixing that is made visible by a colored indicator. Values of the axial dispersion coefficient can be calculated from the measured mixing times.