Unsteady conjugate model of fluid mechanics and mass transfer for butanol pervaporation process by non-porous membrane

摘要

A diffusion-convective mass transfer mathematical conjugated model of butanol recovery from a re-circulating aqueous solution by pervaporation using a polydimethylsiloxane (PDMS) membrane was developed based on computational fluid dynamics. Discretized continuity, linear momentum, and convective-diffusion mass transfer equations were solved by an in-house code based on the finite volume method for a laminar flow with a flat attached non-porous membrane. In addition, a novel numerical procedure to determine the butanol diffusivity in the PDMS membrane was developed based on the solution of the conjugate unsteady convection-diffusion model that included five coupled partial differential equations. The evolution of the distribution of the velocity profile in the fluid flow and the transient variation of butanol concentration in the feed solution and inside the PDMS membrane were determined. Variations in time and space of the dimensionless mass flux along the length of the pervaporation module were calculated from the conjugate convection-diffusion mass transfer model. The numerical predictions of the butanol mass flux in the feed solution exhibited good agreement with the experimental results with an error smaller than 3%. Understanding the mechanisms of mass and fluid transport phenomena by computational modeling can be helpful for improving the design of pervaporation processes.