Hd h9 AK h0J631ci

Equation (6.31c) is shown in Fig. 6.19. No weeping is predicted for points above the correlating curve, while weeping is predicted below it

Weep rate prediction. Lockett and Banik (56) and Hsieh and McNulty (63) proposed correlations for predicting weep rates from sieve trays. Both correlations are based on pilot scale data, mainly with the air-water system. The Hsieh and McNulty correlation is based on a broader data bank, which includes the experimental data by Lockett and Banik. Hsieh and McNulty used an even wider, non-air-water, proprietary data bank for testing some of their predicted trends.

O 20 40 60 80 100 120

O 20 40 60 80 100 120

Figure $.18 Fair's weep point correlation. (From B. D. Smith, Design of Equilibrium Stage Processes. Copyright © 1963 by McGraw-Hill, Inc., reprinted by permission.)

Colwell and O'Bara (58) applied both the Lockett and Banik and the Hsieh and McNulty correlations for estimating tray efficiency under weeping conditions. At low pressu es, use of the Lockett and Banik correlation gave good efficiency predictions, while use of the Hsieh and McNulty correlation gave optimistic efficiency predictions. At high pressures, use of the Hsieh and McNulty c . relation gave good efficiency predictions, while use of the Lockett and Banik correlation gave conservative efficiency predictions. Colwell and O'Bara (58) recommended the Lockett and Banik correlation for low-pressure ( < 165 psia) systems, and the Hsieh and McNulty correlation for high-pressure (>165 psia) systems.

The Lockett and Banik correlation (56) is

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