Influence of microporous membrane properties on the desalination performance in direct contact membrane distillation.pdfVIP

Journal of Membrane Science 513 (2016) 280–293 Contents lists available at ScienceDirect Journal of Membrane Science journal homepage: /locate/memsci In?uence of microporous membrane properties on the desalination performance in direct contact membrane distillation Lin Li, Kamalesh K. Sirkar n Otto H. York Department of Chemical, Biological and Pharmaceutical Engineering New Jersey Institute of Technology Newark, NJ 07102, USA article info Article history: Received 8 December 2015 Received in revised form 10 March 2016 Accepted 5 April 2016 Available online 13 April 2016 Keywords: Direct contact membrane distillation PVDF and ePTFE membranes Wilson Plot Membrane tortuosity Knudsen diffusion/transition regime abstract To evaluate the in?uence of membrane properties on direct contact membrane distillation (DCMD) performance, a variety of microporous hydrophobic ?at sheet membranes of polyvinylidene ?uoride (PVDF) and expanded polytetra?uoroethylene (ePTFE) were employed in this study over a range of hot brine temperatures, 65–85 °C. The membrane thickness was varied between 23 mm and 125 mm; the nominal pore size was varied from 0.05 mm to 0.45 mm; the porosity was generally high in the range of 0.7–0.8. Experiments were done using two different ?at test cells, a stainless steel cell and a chlorinated polyvinyl chloride (CPVC) cell. Boundary layer heat transfer resistances in the membrane cell on both sides of the membrane and the two membrane surface temperatures were determined from the experimental data over a range of hot brine and cold distillate ?ow rates by the Wilson plot technique. Membrane properties such as the maximum pore size and tortuosity were characterized and employed in checking out model assumptions and model results for water vapor transport in the Knudsen regime and the transition region. Good agreements (within 5% deviation) of the membrane mass transfer coef?cient of water vapor and the observed water vapor ?uxes were obtained between the exper