Transport phenomena and fouling in vacuum enhanced direct contact membrane distillation: Experimental and modelling

Abstract

The application of vacuum to direct contact membrane distillation (vacuum enhanced direct contact membrane distillation, V-DCMD) removed condensable gasses and reduced partial pressure in the membrane pores, achieving 37.6% higher flux than DCMD at the same feed temperature. Transfer mechanism and temperature distribution profile in V-DCMD were studied. The empirical flux decline (EFD) model represented fouling profiles of V-DCMD. In a continuous V-DCMD operation with moderate temperature (55 ºC) and permeate pressure (300 mbar) for treating wastewater ROC, a flux of 16.0±0.3 L/m 2 h and high quality distillate were achieved with water flushing, showing the suitability of V-DCMD for ROC treatment. A Thermal conductivity (kW/m·K) P Poiseuille flow diffusion L Membrane module length (m) K Knudsen diffusion ρ Fluid density (kg/m 3 ) m Membrane surface Cp Specific heat capacity of fluid x Transversal (x-direction) λ Latent heat of water z Axial (z-direction) Rm Membrane resistance (Pa.m 2 .h/L) t Time (s)

Evaluating the potential of superhydrophobic nanoporous alumina membranes for direct contact membrane distillation

“…New approaches in designing thermoelectric materials, where the reduction of thermal conductivity is also crucial, might be insightful [72][73][74] . Alternatively, superhydrophobic AAO membranes should be tested in the air gap MD and vacuum MD configurations that are less vulnerable to temperature polarization 75 . This work might advance the rational design of materials and processes for DCMD and thermally driven liquid-vapor extraction, in general.…”

Effect of chemical and physical factors on the crystallization of calcium sulfate in seawater reverse osmosis brine

“…Thus, the effect of 51 solution concentration on permeate flux is less than that of the other desalination processes [3, 52 15]. Additionally, MD possesses several advantages including high rejection of non-volatile components, lower operational pressure when compared to that of reverse osmosis (RO), and lower operating temperature and smaller footprints when compared to those of conventional distillation processes [16][17][18]. Recently, a novel combined process, namely MD with a crystallizer (MDC), is highlighted with an increase in the interest to recover valuable resources from seawater [3,[19][20][21][22][23].…”

Heat and Mass Transport in Modeling Membrane Distillation Configurations: A Review

“…DCMD requires less heat energy when compared to AGMD (Camacho et al, 2013), and is less expensive than SGMD, considering external condenser and air blower cost associated with SGMD configuration (Khayet and Cojocaru, 2013). VMD involves the application of vacuum to permeate side of membrane (El-Bourawi et al, 2006;Lee and Kim, 2013;Zhang et al, 2013;Boutikos et al, 2017;Naidu et al, 2017) to continuously remove vapor from vacuum chamber, which is formed due to vapor pressure difference across the membrane (Khayet and Matsuura, 2011b;Criscuoli et al, 2013). In VMD, condensation occurs in the condensation chamber outside MD module and the applied vacuum pressure is less than the saturation pressure of volatile molecules removed from feed side (Figure 2) (El-Bourawi et al, 2006;Ramon et al, 2009;Mericq et al, 2010).…”