Theoretical prediction methods

Theoretical prediction methods for tray efficiency are based on the two-film theory and use the sequence of steps in Fig. 7.3. Almost all evolved from the AIChE model (84,125,132,133). This model was developed over five years in the late 1950s in three universities. Over the last few decades, several aspects of the AIChE model have been examined, criticized, corrected, and modified. State-of-the-art reviews are given by Lockett (12) and Chan and Fair (134,135). A modified version of the AIChE model that alleviated several of its shortcomings and updated its hydraulic and mass transfer relationships was produced by Chan and Fair (134,135).

The Chan and Fair correlation uses Eqs. (7,13) and (7,16) to calculate the point efficiency Eoa. Values of NG and NL in Eq. (7.13) are obtained using Eq. (7.14). Chan and Fair derived the following equation for kgOi, based on Higbie's penetration theory, observations by Calderbank et al. (136,137), and data regression.

19.1DS5 (1030FF - 867FF2)

(kcr where

The gas residence time t is obtained from

The Chan and Fair correlation uses the Bennett et al. correlation i Sec. 6.3.3) for calculating the clear liquid height hc and the froth density (J> [Eqs. (6.56) and (6.58)]. For calculating kLa,, Chan and Fair use a correlation by Foss and Gerster (138).

Mi = (0.49^ + 0.17) (6000L>£5) The liquid residence time tL is obtained from t, =

0 0

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