WAVE MODEL FOR LONGITUDINAL DISPERSION - ANALYSIS AND APPLICATIONS

An analysis and applications of the wave model for longitudinal disper sion are presented Asymptotic forms of the wave model are considered a nd analytical solutions of typical linear stationary and nonstationary problems of chemical reactor engineering interest are obtained and co mpared to those for the Fickian dispersion model. The wave model leads to efficient analytical solutions for linear problems, which in princ iple differ fr-om the solutions of the Fickian dispersion model; only for slowly varying concentration fields do the solutions of both model s approach each other. Spatial and rime moments of the concentration d istribution are obtained for pulse-dispersion problems; the first thre e spatial moments of the mean, variance, and skewness have exact, larg e-time asymptotic forms in the case of Taylor dispersion. Old experime nts that could not be explained with the standard dispersion model are reconsidered and explained: the change with time of the variance of a concentration pulse when the flow direction is reversed and the diffe rence in values of the apparent axial dispersion coefficient and the b ack-mixing coefficient in a rotating disk contactor: The experimental determination of model parameters is discussed.