# Introduction - dimensional diffusion steady state condition...

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Introduction : The diffusion coefficient depends upon the pressure, temperature and the composition of the system. As one might expect when considering the mobility of molecules, the diffusion coefficient are generally higher for gases than liquids and that of liquids are higher than solids. The diffusion coefficient for the gas may be experimentally measured in a tube. This tube, which is partially filled with pure liquid( A ),is maintained at a constant temperature and pressure. Gas ( B ), which flows across the open end of the tube, has a negligible solubility in liquid ( A ) and is also chemically inert to ( A ). Component ( A ) vaporizes and diffuses into the gas phase. The rate of vaporization may be measured and may also be mathematically expressed in terms of the molar mass flux. Theoretical Background : The diffusion in an evaporation-tube have some assumptions. These are: constant pressure and temperature, constant diffusion coefficient, one-

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Unformatted text preview: dimensional diffusion, steady state condition, axial symmetry, the gas is insoluble and no convection effects. The fundamental diffusion equation is : NA = ( D AB *P )* ( P A1- P A2 ) / ( R * T * P B,lm * h) (1) ) /( ln( ) / ( 2 / A A L AB P P P RT P sM D-= ρ eq. (7) D AB B A AB P M M T D Ω + = 2 2 / 1 2 / 3 / ) / 1 / 1 ( 001858 . σ eq.(8) 2 3 / 1 3 / 1 2 / 1 75 . 1 ] ) ( ) [( / ) / 1 / 1 ( 001 . B A B A AB v v P M M T D Σ + Σ + = Procedure: The water bath was prepared and its temperature was adjusted at 45 o C, then the dry air was flown over the tubes at 720 L/Min. The water balance was adjusted and the pressure and the temperature were recorded. The values of ( h) of each tube were recorded. The first values of ( h ) were recorded at 8:00, then another four values of ( h) were recorded at every hour by the use of the traveling microscope ....
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## This note was uploaded on 09/27/2011 for the course CHEMICAL E CHE 309 taught by Professor M.elgaily during the Fall '09 term at King Fahd University of Petroleum & Minerals.

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Introduction - dimensional diffusion steady state condition...

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