Performance improvements by embedded spacer in direct contact membrane distillation – Computational study

Computational fluid dynamics simulations were conducted in direct contact membrane distillation modules containing a novel spacer design. The net-type spacers with a 45° strand angle and various strand size were embedded between two active layers of the membrane. The embedded spacers create a micro-patterned surface at each side of the membrane that induces local mixing in the vicinity of the surface. The k − ω SST turbulent model was employed to conduct simulations in modules with embedded spacers while the laminar model was employed to conduct simulations in the module containing a flat membrane. The membrane was treated as a functional surface with zero thickness. Dusty-Gas model was applied to determine the vapor permeation rate coupled with the local temperature and concentration over the surface of the membrane. Concentration and temperature polarization were mitigated significantly, and water flux was enhanced by about 40% with the module containing embedded spacers of the larger strand. It is demonstrated here that with mitigation of polarizations and reduction of scaling/fouling propensity direct contact membrane distillation modules containing embedded spacers could be a good candidate for seawater desalination and for treating highly concentrated non-volatile solutions.