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Because of its potential benefits in lowering process energy consumption, freezing desalination as a seawater desalination method has attracted a lot of attention. However, significant mass loss caused by extensive washing is a fundamental problem preventing the development of freezing desalination technologies. For freezing desalination technology to be widely adopted, the washing process must be eliminated. In this study, a fluid-layer-based method for separating ice is introduced. The density differences between the generated ice and the silicon oil intermediate fluid layer facilitate the separation of the product water without the need of conventional crushing or washing processes. The aim of this work is to study the feasibility and applicability of using silicon oil as an intermediary fluid layer in ice separation during the freezing desalination process. The outcomes show promise for a feasible freezing desalination technique utilizing silicon oil as an intermediate separation layer. It was also observed that as feed salinity decreases, the desalination rate increases. For instance, the distillation rate is 50.89 % and 67.3 % at an initial feed salinity equal 45,000 and 10,000 ppm, respectively. Overall, the initial feed salinity and COP are found to have an impact on specific energy usage. • Intermediate fluid layer for ice separation • Silicon oil for ice production in freezing desalination • Specific energy consumption is affected by initial salinity and COP. • Specific energy consumption 57.412 kWh/m3 [ABSTRACT FROM AUTHOR]

Freezing desalination has gained interest due to its potential to reduce energy use. The freezing process faces challenges that limit its wide use. Washing product ice causes a large mass loss. Most freezing processes involve crushing to generate the appropriate ice form, limiting large-scale production. A vacuum pump and pressing piston are experimentally utilized to collect brine during melting to avoid washing and crushing ice. Five brine separation processes are needed to produce 2 %-salinity water. The studies used salinity-varying feed water. From the results, utilizing a vacuum pump and piston for brine separation during melting and a relatively small number of separation steps has considerably enhanced the quality of the produced water without causing significant mass loss. It is observed that 1000 ml of 15,000 ppm feed water produces freshwater with salinity and volume equal to 114 ppm and 185 ml, respectively. Results indicate that when the COP varied from 4 to 6, the system performance ratio increased from 31.74 to 47.62 and 7.94 to 11.90, with a recovery ratio equal to 0.9 and 0.6, respectively. Compared to previously described freeze desalination, MSF, MED, and MD desalination systems, the specific energy consumption increases by 71.5 %, 66.4 %, 54.5 %, and 36.1 %. • Crushing and washing free, freezing desalination technology • A technique that involves brine extraction by vacuum • Experimental investigation at different feed salinities • System performance ratio ranged from 31.74 to 47.62. [ABSTRACT FROM AUTHOR]

Abstract Experiments and Computational Fluid Dynamics (CFD) simulations were performed to investigate the colloidal fouling control of a vibration enhanced reverse osmosis (VERO) membrane system for up to 12 h of operation time. A porous cake mass transfer model for the reverse osmosis (RO) colloidal fouling analysis was derived by combining the cake filtration model, cake enhanced osmotic pressure (CEOP) effect, the critical flux theory, and the solute convection-diffusion model. The process of colloidal particle deposition and fouling formation on the membrane surface were visualized using this model. The permeate flux variation and cake layer distribution along the membrane were depicted. Systematic studies including different initial permeate fluxes, Reynolds numbers, particle concentrations, and vibration frequencies were carried out to investigate the system performance under different operation conditions. The results suggest that colloidal fouling induced permeate flux decline could be improved by the high-frequency vibration in the VERO module. Both simulations and experiments demonstrated that, with a fixed vibration amplitude, membrane module with higher vibration frequencies will have less NaCl accumulation and higher permeate flux under the influence of colloidal fouling. Highlights • The colloidal fouling control performance of the vibration enhanced reverse osmosis technique was investigated. • A cell-based numerical model to analyze the process of membrane colloidal fouling was developed and validated by experiments. • Axial variations of the permeate flux and fouling cake height, the CEOP effect, and critical flux theory were considered. • Membrane colloidal fouling is significantly reduced by the proposed technique based on CFD simulations and experiments. [ABSTRACT FROM AUTHOR]

The performance of a vibration enhanced reverse osmosis membrane module for desalination of artificial seawater was investigated with computational fluid dynamics (CFD) simulations and experiments. The computational model couples fluid dynamics with solutes transport inside the full length domain containing ‘zigzag’ spacers using a two dimensional, transient Large Eddy Simulation turbulence model. Both the local concentration dependent solute properties and variation of permeate flux over the membrane surface were predicted with the model. Membrane local permeate flux, concentration polarization, shear rate, and mass transfer were also calculated. The results suggest concentration polarization in the seawater desalination process could be reduced by imposing vibration on the reverse osmosis membrane. It was determined that the higher the vibration frequency the higher the membrane permeate flux while keeping the vibration amplitude constant. The CFD simulation predictions are validated against experimental data of permeate fluxes with good agreement. [ABSTRACT FROM AUTHOR]

The subject of this work is the development of a novel vibration assisted seawater desalination approach which changes thermodynamic (mass transfer coefficient) and hydrodynamic (cross-flow velocity) properties to mitigate the inorganic fouling for RO membranes. A classical mass transport model and experimental measurements showed that an increased cross-flow velocity in the feed channel enhances the near membrane mass transfer coefficient, which promotes the back-diffusion of inorganic salts and reduces the concentration polarization (CP). Then a theoretical CP Finite Element Method (FEM) model incorporating increased cross-flow velocity reveals that a lower CP modulus forms near the membrane surface with a higher vibration frequency, which results in less fouling on the membrane surface. The vibration assisted desalination process was demonstrated using a linear motor driven, periodically oscillating desalination cell. A smaller flux decline was observed while using a higher vibration frequency (with a constant sinusoidal amplitude) and a higher vibration velocity (in multiple vibration forms). Process simulations and experimental observations validated that the proposed vibration assisted desalination process helps enhance the permeate flux and mitigate the formation of inorganic fouling on the RO membrane surface. [ABSTRACT FROM AUTHOR]