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and where, for the case of the CSTR reactor and regenerator of equal size, T ' G ( t ) = T ' R ( t ) = k?-xtThe approach of Equations (40) and (42) is not exact, but alternate deactivation and reactivation greatly reduces interaction in the second half of a cycle. Thus, a comparison of mean activities calculated from Equations (50') and (55') with those from Petersen's equations (50) and (55) showed the latter to be low by about 25% for the once-through makeup catalyst and by about 3% for the total stream (where p = k, = k, = A, / 3 = 0.1).It is worth noting that although the authors, like Petersen, chose to express activity as a function of time, or age, the problem might have been formulated as proposed by Rudd (Can.

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A semi‐mechanistic model for two phase gas‐liquid slug flow proposed recently by Dukler and Hubbard has been modified and extended to apply to the entire intermittent flow regime. Flow predictions of the model proposed in this paper are compared with detailed experimental data recently obtained for an air‐oil system. The model requires the use of empirical correlations for the slug velocity and the in situ liquid volume fraction in the slug. In addition, either the slug frequencies or length corresponding to the given design conditions must be known. However, calculated values of average pressure gradient and in situ liquid volume fraction are relatively insensitive to these latter parameters, and in fact, good results are obtained assuming a constant slug length. The paper includes a discussion of the limitations of the proposed model and the expected direction of further study required to extend its mechanistic aspects.

Using a mechanistic approach, equations are developed to describe the stratified cocurrent flow of gas‐liquid mixtures in horizontal pipes. An iterative method is suggested for their solution. Experimental data were collected using air‐oil mixtures in a one inch 1. D. by 101 ft. long acrylic pipe. Pressure drop and average in situ liquid volume fraction are presented as a function of the superficial gas velocity and are compared with predicted results from this study and other models reported in the literature. Visual observation of flow patterns and their transitions are indicated on the tentative flow pattern map of Govier and Aziz(1).