Axial dispersion in the gas and liquid phases

To this author s knowledge, no data are currently available on the RTD in the gas phase for cocurrent gas-liquid upflow through a packed column For unpacked bubble-columns with large length-to-diameter ratios, the gas phase is usually assumed to be in plug flow. The same should be true for the bubble-flow regime in a packed bubble-column. 

gas flow rate ) cylindrical A Min. gas flow rate f column 

Stiegel and Shah35 found that the Peclet number was somewhat dependent upon the bed height. Unlike the unpacked bubble-column, the above correlation indicates that the axial dispersion coefficient in a packed bubble-column is dependent upon the liquid velocity. 

One common feature of the studies described above is that they all indicate that the axial dispersion in the liquid phase (and the same should be true for the gas phase) of a packed bubble-column is considerably smaller than that obtained in the liquid phase of an unpacked bubble-column under equivalent flow conditions. 

Stiegel and Shah34 measured the liquid-phase axial dispersion coefficient in a packed rectangular column. Some details of system conditions used in this study have been described earlier, in Sec. 7-3. The axial dispersion coefficient and the liquid-phase Peclet number were correlated to the gas and liquid Reynolds numbers by the expressions 

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