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.
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Nonfoaming regular systems | |||
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