VALIDITY AND LIMITATIONS OF THE CLOSED-VESSEL ANALYTICAL SOLUTION TO THE AXIAL-DISPERSION MODEL

The validity and limitations of the pseudo-analytical solutions of the axial dispersion model, for the "closed-closed" boundary conditions, are examined in conjunction with the determination of the Peclet number and the corresponding axial dispersion coefficient; the first ten roots of the transcendental equation related to them are calculated and tabulated. The generation of theoretical RTDs by differentiation of the washout profile is shown lo be superior to the use of the analytical equation available for a Dirac delta impulse, for values of the Peclet number < 10. For Pe > 16, the analytical solution for the "open-open" boundary conditions may be used, instead. For the intermediate region (10 < Pe < 16), the Pe corresponding to the "open-open" boundary conditions may be determined and then corrected using the correlation of Ityokumbul et al. (Chem. Eng. Sci. 43, 2457 (1988).