Flood trays fractional hole area

Entrainment flooding is predicted by an updated version of the Souders and Brown correlation. The most popular is Fair s (1961) correlation (Fig. 20), which is suitable for sieve, valve, and bubble-cap trays. Fair s correlation gives the maximum gas velocity as a function of the flow parameter (L/G)V(Pg/Pl), tray spacing, physical properties, and fractional hole area. 

Figure 6.9 Factors affecting the flood capacity factor. FRI sieve tray test data, DT 4 ft, S = 24 in, hw = 2 in, dH = 0,5 in, straight downcomers, AJAT = 0.13. (a) Effect of liquid rate, Af = 0,08, (i>) Effect of fractional hole area. Cydohexane-Af-heptane, 24 psia.

Fair s correlation (19, Fig, 6.10). The Fair flood has been the standard of the industry for entrainment flood prediction and was recommended by most designers (5,11,18,30-33). CSB is a function of the flow parameter Fu [Eq, (6.7)], tray spacing, surface tension, and fractional hole area. CSB is based on the net area AN, and is evaluated from Fig. 6.10, The flooding vapor velocity is calculated from... 

Figure T.10 Some factors affecting sieve tray efficiency. FRI data, total reflux, DT = 4 It, S = 24 in, hu, = 2 in, dH = 0.5 in. Both parts show a small efficiency rise with pressure. Both parts show little effect of vapor and liquid loads above about 40 percent of flood, (a) Showing efficiency reduction when fractional hole area is increased from 8 to 14 per-cent of the bubbling area (6) emphasizing little effect of vapor and liquid loads, and an efficiency increase with pressure. Af 0.14 (Both parts repeated with permission from T. Yanagi and If. Sakata, lad. Eng. Chan. Proc. Use. Dev. 21, p. 712, copyright 19S2, American Chemical Society.)...

Valve trays. Manufacturer literature contains correlations for entrainment flooding (7-9). The three sieve tray correlations above are also applicable to valve trays. Of the three, the author recommends the Easter and Haas (15) correlation because it was specifically extended for valve trays and because it possesses the advantages listed above. When applying this correlation to valve trays, is the fractional hole area when all valves are open, i.e.,... 

Sieve trays with 10% hole area and 0.5 cm diameter holes will be used. Trays are available in standard diameters of 0.25 m increments (0.25,0.50, 0.75, 1, 1.25, 1.50,. .., m). Based on the top tray conditions, determine the required tray diameter rounded up to the nearest larger standard size. Assume a tray spacing of 0.5 m, a foaming factor of 0.80, and a fraction of flood of 0.80. The liquid density is given as 730 kg/m and the vapor density may be estimated based on the ideal gas equation. The liquid surface tension is 27 dynes/cm. 

The column has 3 m diameter sieve trays with 0.5 cm diameter holes and 10% hole area. The tray spacing is 45 cm. Assuming a foaming factor of 0.85, calculate the vapor flood velocity at the top tray. Check if the column diameter is acceptable. The fraction of flood velocity should be within a 60-85% range. 

Sieve trays will be used with 60 cm spacing, 6 cm weir height, 0.6 cm hole diameter, 0.25 cm tray thickness, 5 cm downcomer clearance, and hole area 10% of the total tray area. The foaming factor is 0.80 and the froth density in the downcomer is 0.5. The target fraction of flood velocity is 0.70. 

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