ProblemSet8_soln_19.pdf - ECH 141 Problem Set#8 1 Two...

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ECH 141 Problem Set #8 1. Two immiscible liquids A and B of specific gravities 0.8 and 1.0, respectively, flow into a closed tank in which they separate into two layers. Pure A and pure B are taken off by pipes which discharge to atmosphere at a point 5 ft below the A/B interface in the tank. The flow in each pipe is controlled by an orifice. Calculate the size of the orifice discharging B when the one discharging A is 1 inch in diameter and the total feed is 5000 lbs/hr containing 60% by weight of A. The outlet pipes are nearly identical, and are much larger than the orifices. The orifice discharge coefficients are each C D =0.6, so that if the head loss across the orifice is h O , then the velocity v through the orifice is given by the orifice equation (similar to Torricelli’s law, see Eq. (8.5-15) in text), v = C D 2gh O . Note that since h O = 1 C D v 2 2g , this orifice equation corresponds to a loss coefficient K (i.e., fraction of velocity head loss) of 1/C D . It may be assumed that none of the head loss across the orifices is recovered and that both fluids have negligible vapor pressure. Neglect all frictional losses except for the losses in the orifices. For water, assume that ρ g = 62.4 lb f ft 3 (water)

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