Sept_27_10_58_AM_AJH_HW5_v2__1_ - Chemical Engineering...

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Page 1 of 1 Chemical Engineering 150B- Fall 2005 Problem Set #5 Due MONDAY October 3 rd , 2005 Note: There are 3 problems in this assignment (see back). Problem 1. (20 points) In a vertical wetted-wall tower operating at steady-state, ammonia, NH 3 , is stripped from an ammonia-water solution into an air stream. The overall gas coefficient, K G , is 3.12 x 10 -9 (kg mole) / (m 2 s Pa). At a horizontal plane in the tower, the bulk concentration of the falling aqueous stream is 4 kg mole/m 3 of solution and the bulk partial pressure of ammonia in the rising gas stream is 3.04 x 10 3 Pa. For dilute solutions of ammonia in water at the operating temperature, the equilibrium partial pressure may be evaluated by ,, 3 1360 / Ai Pa p c kg mole m = If the gas phase offers 75% of the total resistance to mass transfer, calculate at this horizontal plane in the tower: (a) the individual gas-film coefficient, k G ; (b) the overall liquid-film coefficient, K L ; (c) the individual liquid-film coefficient, k L ; (d) the interfacial concentrations, p A,i , and c A,i ; Problem 2. (20 Points) A solid pole, 0.05 m in diameter and 5.0 m tall, is spray painted on the surface parallel to its axis with a very thin coat of paint. The paint primarily contains the solvent benzene. The vapor pressure of the benzene at 298 K is 1.34 x 10 4 Pa. The estimated loading of solvent in the wet paint on the pole is 0.12 g of benzene per cm 2 of cylinder surface. Determine the minimum time to dry the painted pole if dry air at 298 K and 1.013 x 10 5 Pa pressure flows normal to pole axis at a velocity of 1 m/s.
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This homework help was uploaded on 04/02/2008 for the course CHEM 150b taught by Professor Bell during the Spring '08 term at University of California, Berkeley.

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Sept_27_10_58_AM_AJH_HW5_v2__1_ - Chemical Engineering...

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