Abstract:

Computational fluid dynamics simulations and experiments were conducted to study the performance of distillation membrane process for water treatment and desalination applications. Polarizations and fouling/scaling in a direct contact membrane distillation module were examined. Laminar and turbulent flow regimes in the feed and permeate channels were considered. The hydrophobic membrane separates feed and permeate channels. The membrane is treated as a functional surface where the permeate flux is modeled as a function of local temperature, concentration using the Dusty-Gas diffusion model. The combination of Knudsen and viscous diffusion governs the vapor transport through the membrane. Vaporization occurs in the feed channel at the entrance of pores of the membrane due to the well-known confinement (surface tension) effect. Vapor is pushed through the membrane by the partial pressure difference created by the temperature concentration difference across the membrane. The permeability (resistance) of the membrane depends strongly on the membrane thickness, porosity, pore size, and tortuosity. Mitigation of polarizations and fouling/scaling and the optimization of module design will be presented and discussed.