D downcomer froth height is operation acceptable or

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Unformatted text preview: At the top of the column, the reflux rate is 1.3(0.947)(768) = 945 lbmol/h. The overhead vapor rate = 1.3[0.947(768) + 768] = 1,944 lbmol/h. Use the entrainment flooding correlation of Fig. 6.24, with densities from a simulation program, where the abscissa is, FLV LM L V = VM G L 1/ 2 = 945(30.9) 0.0703 1,944(30.9) 47.2 1/ 2 = 0.0192 (1) From Fig. 6.24, for 24-inch tray spacing, CF = 0.38 ft/s. Because FLV < 1, Ad /A = 0.1. FHA = 1.0, FF = 1.0, and since = 20 dynes/cm, FST = 1.0. From Eq. (6-24), C = FSTFFFHACF = (1)(1)(1)(0.38) = 0.38 ft/s From Eq. (6-40), U f = C L - V / V 1/ 2 = 0.38 47.2 - 0.0703 / 0.0703 1/ 2 = 9.84 ft / s From a rearrangement of Eq. (6-44), solving for the fraction of flooding, 4VMV 4(1,944 / 3,600)(30.9) f = 2 = 2 = 0.95 or 95% Unacceptable! D U f 1 - Ad / A V 6 (9.84)(314)(1 - 01)(0.0703) . . At the bottom of the column, the boilup rate from Exercise 7.41 is 1.3(1.138)(1,209) = 1,789 lbmol/h. The liquid rate leaving the bottom tray = 1.3(1,376 + 1,201.9) = 3,351 lbmol/h....
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This note was uploaded on 09/08/2008 for the course CHE 244 taught by Professor Selebi during the Spring '06 term at Lehigh University .

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