Unsteady-State Interphase Diffusion

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This Demonstration considers the mass transfer of a substance A between two immiscible solvents I and II. The concentration in both phases is plotted versus position for various values of the diffusion coefficients (in , and , time (in seconds), and Henry law constant (a dimensionless constant). When the concentration of A is continuous at the interface, which is not typical. The concentration profiles are solutions of the following diffusion equations and boundary conditions:




for ,

for , ,

at ,

at ,

at .

Using Laplace transforms, one can easily derive analytical expressions of the concentrations in phases I and II:




Contributed by: Housam Binous (March 2011)
Open content licensed under CC BY-NC-SA



R. B. Bird, W. E. Stewart, and E. N. Lightfoot, Transport Phenomena, New York: Wiley, 1960.

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