Ninety-five percent of the acetone vapor in an 85 vol.% air stream is to be absorbed by countercurrent contact with pure water in a valve-tray column with an expected overall tray efficiency of 50 %. the column will operate essentially at 20 ºc and 101 kpa pressure. equilibrium data for acetone-water at these conditions are: mole percent acetone in water 3.30 7.20 11.7 17.1 acetone partial pressure in air, torr 30.00 62.80 85.4 103.0 calculate:

(a) the minimum value of s/g, the ratio of moles of water per mole of air.

(b) the number of equilibrium stages required using a value of s/g of 1.25 times the minimum. ( indicate operating line obviously)

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?