Weir Constriction Correction Factor

Sieve Trays
Figure 12-4 Height of vapor-free liquid in the downcomer of a single-pass sieve tray with crossflow.
Correction Factor Cross Flow
Figure 12-5 The correction factor for effective weir length. [W. L. Bolles, Pet. Refiner, 25:613 (1946), by courtesy Hydrocarbon Process.]

weir constriction correction factor equivalent height of clear liquid, in length of weir, in liquid flow rate, gal/min

A graph for evaluation of the correction factor Fw is presented in Fig. 12-5. The factor Fw is used to correct for the distorted flow pattern of the liquid as it approaches the weir.

When the crest over a straight segmented weir is less than a quarter of an inch, Fair et al.2 recommend the use of a serrated weir, and for weirs of this type

where 0 is the angle of serration and the other symbols are defined beneath Eq. (12-8).

calculation of h09 the head equivalent to the dry hole pressure drop

The dry hole pressure drop for a sieve tray may be calculated by use of the following equation for thick plate orifices fc0 = 0.186(^-)2— (12-10)

\co/ Pl where h0 = dry hole pressure drop of vapor across the perforations in inches of equivalent vapor-free liquid u0 = linear velocity of the vapor through the perforation in feet per second

Values of the discharge coefficient C0 are given by the chart presented in Fig. 12-6 which was prepared by Leibson et al.12

where Fw =

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