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Mass-transfer characteristics were measured for the Mellapak structured packing series 250Y, 350Y, 452Y, and 500Y. k L a was measured by oxygen desorption from water and the effective mass-transfer area a by absorption of CO 2 into NaOH solution and also by oxygen absorption into a sulfite solution. Using Bodenstein numbers determined by means of the "cold" airÀwater dynamic experiments, effects of gas-and liquid-phase axial mixing on the characteristics were evaluated for Mellapak 250Y. Strikingly large differences found between the mass-transfer parameters and their flow dependencies measured in this work and those predicted by models especially designed for the prediction of the parameters in corrugated sheet structured packings (Billet, R.;

The "profile method" enables the determination of vapor-and liquid-side volumetric mass-transfer coefficients k V a and k L a by comparing the concentration profiles measured in both phases in a distillation column with the simulated profiles. The method is based on the fact that the shape of the concentration profiles along the column depend significantly on the distribution of the mass-transfer resistance between the liquid and vapor phases. This makes it possible to measure k L a and k V a directly in the distillation columns, in the same manner that is possible in absorption columns, and therefore to validate the distillation models more conclusively than by means of comparing the experimental and calculated height equivalent to a theoretical plate values. The coefficients were measured on structured packing Mellapak250Y. A small axial mixing of phases on this type of packing enables the use of a plug-flow model for both phases. Three distillation systems, methanol-ethanol, ethanol-propanol, and methanol-propanol, were used under total reflux and atmospheric pressure. Samples of the phases were withdrawn directly from the column packing by means of special sampling devices. The dependence of the individual transport coefficients on the phase flow rate was obtained by changing the reboiler duty. The dependencies were compared with those predicted by the following three mass-transfer correlations developed for packed columns: RBF (Rocha et al.

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