Ultrasonic technology is successfully applied to enhance the permeate flux
of membrane distillation. In this study, two major mechanisms of ultrasonic
enhancement on membrane distillation, ultrasonic cavitation and acoustic s
treaming, are formulated in an analytical modeling. Ultrasonic induced memb
rane vibration, acoustic energy dissipation in viscous fluid, and membrane
absorption and transmission of acoustic energy are also included in the mod
eling approach. Based on this model, effects of ultrasonic intensity, ultra
sonic frequency, solution temperature and excited membrane area on permeate
flux of membrane distillation are theoretically analyzed. It is found that
the enhancement ratio can be improved by increasing ultrasonic intensity,
decreasing ultrasonic frequency or decreasing the solution temperature. The
current study also demonstrates that an enhancement up to 200% can be reac
hed with an ultrasonic intensity from 0 to 5 W/cm(2). (C) 2000 Elsevier Sci
ence B.V. All rights reserved.