Pg

QlPl hct

PL pG

The terms in Eqs. (14-94) through (14-96) are in the metric units described in the Nomenclature table at the beginning of this section.

The recommended range of application of the correlation is given in Table 14-10. The clear liquid height at the froth-to-spray transition hct is calculated using the corrected Jeronimo and Sawistowski [Trans. Inst. Chem. Engnrs. 51,265 (1973)] correlation as per Eqs. (14-82) to (14-84).

For decades, the Fair correlation [Pet/Chem. Eng., 33(10), 45 (September 1961)] has been used for entrainment prediction. In the spray regime the Kister and Haas correlation was shown to be more accurate [Koziol and Mackowiak, Chem. Eng. Process., 27, p. 145 (1990)]. In the froth regime, the Kister and Haas correlation does not apply, and Fair's correlation remains the standard of the industry. Fair's correlation (Fig. 14-34) predicts entrainment in terms of the flow parameter [Eq. (14-89)] and the ratio of gas velocity to entrainment flooding gas velocity. The ordinate values T are fractions of gross liquid downflow, defined as follows:

where e = absolute entrainment of liquid, mol/time

Lm = liquid downflow rate without entrainment, mol/time

Figure 14-34 also accepts the validity of the Colburn equation [Ind. Eng. Chem., 28,526 (1936)] for the effect of entrainment on efficiency:

Ea E

where Emv = Murphree vapor efficiency [see Eq. (14-134)]

Ea = Murphree vapor efficiency, corrected for recycle of liquid entrainment

The Colburn equation is based on complete mixing on the tray. For incomplete mixing, e.g., liquid approaching plug flow on the tray, Rahman and Lockett [I. Chem. E. Symp. Ser No. 61, 111 (1981)] and Lockett et al. [Chem. Eng. Sci., 38, 661 (1983)] have provided corrections.

TABLE 14-9 Derating ("System") Factors

System

Factor

Reference Notes

Nonfoaming regular systems

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