EFFECT OF UPSTREAM PRESSURE ON THE FLUX OF SINGLE PERMEANT IN PERVAPORATION

The effect of the upstream pressure on the pervaporation flux of water was studied both theoretically and experimentally. The increase in th e pervaporation flux with an increase in the upstream pressure was pre dicted using newly developed transport equations that allow the pressu re change across the membrane and include both liquid and vapor phase transport. The conventional solution-diffusion model, on the other han d, fails to predict the effect of the upstream pressure, particularly when an assumption is made that the pressure of the permeant inside th e membrane is constant across the membrane and is equal to the upstrea m pressure. The pervaporation flux of water through a polydimethysilox ane membrane and an aromatic polyamide membrane was found, experimenta lly, to increase with an increase in the upstream pressure.