Example 10: Entrainment Effect on Tray Efficiency For the column in Example 9, estimate the efficiency loss should the operation be pushed from the design 80 percent of flood to 90 percent of flood. The midrange dry Murphree tray efficiency is 70 percent.
Solution The vapor and liquid densities and L/V ratio remain unchanged from Example 9, and so is the flow parameter (calculated 0.021 in Example 9). At 80 and 90 percent of flood, respectively, Fig. 14-34 gives y = 0.15 and 0.24. The respective efficiency reductions are calculated from Eq. (14-98),
Flow regime Pressure Gas velocity Liquid flow rate Gas density Liquid density Surface tension Liquid viscosity Tray spacing Hole diameter Fractional hole area Weir height
20-1200 kPa (3-180 psia) 0.4-5 m/s (1.3-15 ft/s) 3-40 m3/(m'h) (0.5-4.5 gpm/in) 0.5-30 kg/m3 (0.03-2 lb/ft3) 450-1500 kg/m3 (30-90 lb/ft3) 5-80 mN/m 0.05-2 cP
400-900 mm (15-36 in) 3-15 mm (0.125-0.75 in) 0.07-0.16
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