Desalination by membrane distillation: A comparative study of tubular and hollow fibre membrane units

Membrane distillation was considered as an alternative to traditional desalination processes because this technique produces ultra-pure water without requiring high temperatures nor high pressures.; The driving force of membrane distillation is a temperature difference across a microporous membrane leading to a vapour pressure gradient. Hydrophobic membranes are used for membrane distillation in order to permit the passage of vapours through the pores while preventing the liquid phase from passing.; The thickness of the membrane is a key variable which affects heat and mass transfers between the warm feed side and cooling side. In this thesis, a module with thin-walled hollow fibres was compared to a module with thicker tubular membranes. The permeate flux produced was compared at different operating conditions. Feed and cooling water flow rates and temperatures were varied. The impact of salt concentration in the feed was also examined.; Different models based on first principles were developed and compared to a semi-empirical model based on the experimental determination of the mass transfer coefficient. Their predictions were compared with experimentally obtained permeate fluxes.