From example 37 the diffusivity of methanol in water

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Unformatted text preview: nstead of American Engineering) units, 1 1 HL = CL 12 = 0.174 1/ 6 4hL DL au L 1/ 2 uL a a 1 1 = 1.08 12 aPh 1/ 6 4(0.0162)(0.947) (3.0 10-9 )(86.8)(0.00274) 1/ 2 0.00274 86.8 a aPh a m aPh To compute (aPh /a), we need for the liquid phase, the Reynolds, Weber, and Froude numbers from equations (6-138), (6-139), and (6-140), respectively, based on the packing hydraulic diameter from (6-137). d h = packing hydraulic diameter = 4 0.947 =4 = 0.0436 m = 0.143 ft 86.8 a Reynolds number = N ReL , h = u L d h L (0.00898)(0.143)(48) = = 262 [(0.35)(0.000672)] L Take the surface tension of methanol at 154oF as = 17 dynes/cm = 0.001165 lbf/ft or 0.001165(32.2) = 0.0375 lbm/s2 Weber number = N WeL ,h 2 u L L d h ( 0.00898 ) (48)(0.143) = = = 0.0148 0.0375 2 2 Froude number = N FrL , h ( 0.00898) = 0.0000175 u2 = L = gd h 32.2(0.143) From (6-136), aPh -1/ 2 = 1.5 ( ad h ) N Re L ,h a = 1.5 [ (86.8)(0.0436) ] ( ) (N -0.2 -1/ 2 We L , h ) (N ) 0.75 FrL , h -0.45 ( 262 ) ( 0.0148) ( 0.0000175) -0.2 0.75 -0.45 = 1.485 Exercise 7...
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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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