A model for axial mixing in reciprocating plate columns

Axial mixing in reciprocating plate columns with different plate geometry has been investigated for single-phase flow. Data are presented on the steady-state concentration profile of a salt tracer around a single reciprocating plate and between two reciprocating plates in a 5 cm diameter column. These data show the existence of two separate hydrodynamic regions in which there are two mechanisms for axial dispersion. One region is in the volume swept out by the reciprocating plate; here the axial mixing is high. The other region is between the plates, where the amount of axial mixing is significantly lower. A model is proposed based on the observed flow structure which accounts for the effects of flowrate, frequency, amplitude, plate spacing, hole size and fractional free area. There are only two adjustable parameters in the model, which are estimated independently from the concentration profile between the plates. The predictions of this model also compare favourably with published data on other reciprocating plate column geometries.