A comparative study of membrane properties modeling used in vacuum membrane distillation theoretical studies

In this study, a theoretical model for the transport phenomena in a vacuum membrane distillation (VMD) unit used for desalination was developed. The model is based on the conservation equations for the mass, momentum, energy and species within the feed saline solution with coupled boundary conditions, as well as on the mass and energy balances on the membrane sides. The slip velocity and temperature jump boundary conditions due to the membrane's hydrophobicity were also taken into consideration. All combinations of effective thermal conductivity and tortuosity models, usually used in membrane distillation modeling are studied and discussed to show their adequacy with experimental data from the literature for PVDF, PTFE, and PP hydrophobic membranes used in VMD devices. It was found that neglecting slip velocity and temperature jump boundary conditions leads to an underestimation of the permeate flux. In addition, many effective thermal conductivity and tortuosity model combinations overestimate or underestimate the experimental data for pure water production, while others seem to fit it better.