(652e) Coupling Between Lumen, Shell, and Membrane Mass Transfer Resistances

Mass transfer rates in hollow fiber membrane modules often are controlled by the membrane resistance. However, resistances in the contacting fluid in the lumen or shell may be significant as well. Fluid resistances in dialysis, pervaporation, reverse osmosis and other processes with a contacting liquid phase often are important. Although less common, fluid resistances can be significant in gas separations such as dehydration if the membrane permeance is sufficiently large.

Theoretical predictions of fluid phase resistances, or mass transfer coefficients, typically are based on assumptions of constant concentration or mass flux at the membrane surface. Mass transfer coefficients are highly dependent on the boundary condition used. Moreover, the variation in concentration along the membrane surface that occurs with fluid contacting is rarely considered in the analysis.

We present the results of theoretical studies of mass transfer in hollow fiber membrane modules with co and counter-current fluid contacting. Mass transfer coefficients in the lumen and shell can change dramatically from predictions with constant wall concentration or flux and the differences are dependent on fluid contacting. Correlations that account for these differences are proposed.