THE EFFECT OF THE EMBEDDED SPACERS ON THE PERFORMANCE OF DIRECT CONTACT MEMBRANE DISTILLATION SYSTEM OPERATING WITH DIFFERENT INLET FEED TEMPERATURE

摘要

Computational fluid dynamics simulations are used to model the effect of the inlet feed temperature in direct contact membrane distillation modules. Embedded spacers are used as a local mixing promoter tool. Net-type spacers of angle 45° are used as spacers. The presence of the spacers will mitigate the temperature and concentration polarization effects. The calculation of the vapor flux through the membrane is based on the Dusty-Gas model. The membrane is considered as a functional surface, and the embedded spacers are treated as impermeable surfaces. The vapor flux equation couples the variation of the vapor flux in the feed and the permeate channel with the variation of the feed concentration along the membrane. The flow is considered turbulent in channels containing embedded spacers. The k - ω SST turbulent model is used to characterize the steady-state turbulent structures inside the flow channels. The flow rate in the feed and the permeate channels is fixed. The membrane properties are also fixed. The inlet feed temperature is varying while fixing the inlet permeate temperature. The results indicate that the embedded spacers increase the vapor flux permeation while the temperature and concentration polarizations are mitigated. As the inlet feed temperature is increased, the effect of the embedded spacers becomes more significant.