Dispersion in trickle and two-phase flow in packed columns

The coefficients of axial and radial dispersion in both trickle and two-phase flow have been measured for a range of spherical packings, and for $\text{case1}\text{2}$ in., 1 in. and 1$\text{case1}\text{2}$in. Raschig rings packed in 0.10 m and 0.30 m dia. columns. The coefficients were estimated from the dispersion of a pulse of tracer injected from a small tube on the axis of the column and measured before the trace material had dispersed to the wall. Under these conditions the dispersion coefficients so found are not affected by wall flow of liquid, and therefore the coefficients of axial dispersion are generally smaller than those found by other investigators who estimated coefficients for overall dispersion and so included the effect of wall flow in their estimates.Liquid hold-up within the column was measured from the change in the first moment of the injected dispersed pulses. Liquid hold-up for conditions of trickle flow is given in the form of a correlation of dimensionless groups.