Hydrodynamics of a thermopervaporation flow membrane module with cylindrical spacers

The influence of hydrodynamic flow of a butanol-water mixture on the thermopervaporation (TPV) permeate flux and the separation factor has been theoretically and experimentally studied. A possibility of enhancement of thermopervaporation with cylindrical spacers placed in the feed channel or with pulsating feed flow is illustrated by the example of thermopervaporation of a dilute 1-butanol aqueous solution through a PTMSP membrane in a plate-and-frame module. The flow and concentration fields in the planeparallel channel with cylindrical spacers arranged normally to the flow direction have been obtained by numerical solution of the Navier-Stokes and convection diffusion equations. The pressure drop in the channel and the normal diffusion flux of the target component at the feed side of the membrane, depending on the feed flow rate, have been calculated. It has been shown that even two cylindrical spacers can noticeably increase the diffusion flux to the membrane. It has been found that the spacer cross section shape (circular, elliptic, or rectangular) has a minor effect on the mass transfer and pressure drop in the channel. Multifilament highly porous spacers (fiber bundles), which advantageously exhibit a significantly lower resistance to flow compared with impermeable spacers with the same cross section, have been found to provide the maximum enhancement of the diffusion flux.