The Effect of the Embedded Spacers on the Performance of Direct Contact Membrane Distillation System Operating With Different Inlet Feed Temperature

2019 ◽  
Author(s):  
Anas M. Alwatban ◽  
Ahmed M. Alshwairekh ◽  
Umar F. Alqsair ◽  
Robert Krysko ◽  
Abdullah A. Alghafis ◽  
...  
Keyword(s):  
Direct Contact ◽  
Membrane Distillation ◽  
Membrane Properties ◽  
Functional Surface ◽  
Feed Concentration ◽  
Turbulent Structures ◽  
Vapor Flux ◽  
Direct Contact Membrane Distillation ◽  
Dynamics Simulations ◽  
Feed Temperature

Abstract 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.

The Effect of Mixing Promotors on Sweeping Gas Membrane Distillation System Performance

2019 ◽  
Author(s):  
Umar F. Alqsair ◽  
Anas M. Alwatban ◽  
Ahmed M. Alshwairekh ◽  
Robert Krysko ◽  
Abdullah A. Alghafis ◽  
...  
Keyword(s):  
Flow Rate ◽  
Membrane Distillation ◽  
Membrane Properties ◽  
Functional Surface ◽  
Feed Concentration ◽  
Turbulent Structures ◽  
Vapor Flux ◽  
Temperature Polarization ◽  
Dynamics Simulations ◽  
Sweeping Gas

Abstract Computational fluid dynamics simulations were conducted to model the effect of adding mixing promoters in sweeping gas membrane distillation modules. Net-type spacers of 45° are placed in the feed side while membrane corrugation is employed with the tips of the corrugation pointing towards the permeate side. The membrane corrugation is of chevron type. The membrane is considered as a functional surface, and the vapor flux through the membrane is modeled using the Dusty-Gas model. The vapor flux equation couples the vapor pressure variation across the membrane with the feed concentration. The flow inside the channels with mixing promoters is considered turbulent. The k–ω SST turbulent model is used to model the steady-state turbulent structures inside the channels. The flow rate in the feed side is fixed, and the flow rate in the permeate channel is varied so that Rep = 1000,1500, and 2000 are considered. The inlet feed and permeate temperatures, and the membrane properties are fixed. The results indicate that the presence of mixing promoters increases the vapor permeation through the membrane by alleviation of the concentration and temperature polarization effects. The mixing promoters are more effective at high flow rates in both channels.

scholarly journals An Improved Modelling Approach for the Comprehensive Study of Direct Contact Membrane Distillation

Membranes ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 308
Author(s):  
Abolfazl Ansari ◽  
Saman Kavousi ◽  
Fernanda Helfer ◽  
Graeme Millar ◽  
David V. Thiel
Keyword(s):  
Thermal Efficiency ◽  
System Performance ◽  
Direct Contact ◽  
Performance Metrics ◽  
Water Flux ◽  
Membrane Distillation ◽  
Membrane Properties ◽  
Feed Concentration ◽  
Direct Contact Membrane Distillation ◽  
Feed Temperature

Direct Contact Membrane Distillation (DCMD) is a promising and feasible technology for water desalination. Most of the models used to simulate DCMD are one-dimensional and/or use a linear function of vapour pressure which relies on experimentally determined parameters. In this study, the model of DCMD using Nusselt correlations was improved by coupling the continuity, momentum, and energy equations to better capture the downstream alteration of flow field properties. A logarithmic function of vapour pressure, which is independent from experiments, was used. This allowed us to analyse DCMD with different membrane properties. The results of our developed model were in good agreement with the DCMD experimental results, with less than 7% deviation. System performance metrics, including water flux, temperature, and concentration polarisation coefficient and thermal efficiency, were analysed by varying inlet feed and permeate temperature, inlet velocity, inlet feed concentration, channel length. In addition, twenty-two commercial membranes were analysed to obtain a real vision on the influence of membrane characteristics on system performance metrics. The results showed that the feed temperature had the most significant effect on water flux and thermal efficiency. The increased feed temperature enhanced the water flux and thermal efficiency; however, it caused more concentration and temperature polarisation. On the other hand, the increased inlet velocity was found to provide increased water flux and reduced temperature and concertation polarisation as well. It was also found that the membrane properties, especially thickness and porosity, can affect the DCMD performance significantly. A two-fold increase of feed temperature increased the water flux and thermal efficiency, 10-fold and 27%, respectively; however, it caused an increase in temperature and concertation polarisation, at 48% and 34%, respectively. By increasing Reynolds number from 80 to 1600, the water flux, CPC, and TPC enhanced by 2.3-fold, 2%, and 21%, respectively. The increased feed concentration from 0 to 250 [g/L] caused a 26% reduction in water flux. To capture the downstream alteration of flow properties, it was shown that the ratio of inlet value to outlet value of system performance metrics decreased significantly throughout the module. Therefore, improvement over the conventional model is undeniable, as the new model can assist in achieving optimal operation conditions.

Comparison of Sweeping Gas and Direct Contact Membrane Distillation: Module Length Effect

2020 ◽  
Author(s):  
Umar F. Alqsair ◽  
Ahmed M. Alshwairekh ◽  
Anas M. Alwatban ◽  
Robert Krysko ◽  
Alparslan Oztekin
Keyword(s):  
Direct Contact ◽  
Three Dimensional ◽  
Concentration Field ◽  
Local Variation ◽  
Membrane Distillation ◽  
Membrane Properties ◽  
Effect Of Temperature ◽  
Vapor Flux ◽  
Direct Contact Membrane Distillation ◽  
Sweeping Gas

Abstract Computational fluid dynamics simulations are conducted to compare the effect of module length in sweeping gas and direct contact membrane distillation systems for seawater desalination processes. In this work, the effect of temperature and concentration on the flux performance and temperature and concentration polarization characteristics are studied. CFD simulations are conducted in a three-dimensional module to characterize the steady-state velocity, temperature, and concentration field in the feed and permeate channel. The Reynolds number for the feed and the permeate stream is set to 500 and 1500, and thus the laminar flow model is adapted for each channel. The membrane properties are fixed in all cases considered. It is revealed that the local variation of the vapor flux, TPC, and CPC varies with module length in SGMD systems. However, the average values along the membrane in both module lengths do not vary much. Remedies for mitigating temperature polarization should be considered for future studies.

scholarly journals Direct Contact Membrane Distillation for Desalination Brine Solution

2018 ◽  
Vol 24 (11) ◽  
pp. 18
Author(s):  
Asrar Abdullah Hassan ◽  
Ahmed Khalid Mohammed Reda
Keyword(s):  
Direct Contact ◽  
High Salinity ◽  
Membrane Distillation ◽  
Feed Concentration ◽  
Modus Operandi ◽  
Brine Solution ◽  
Direct Contact Membrane Distillation ◽  
Flat Sheet ◽  
Plate Cell ◽  
Feed Temperature

Desalination is a process where fresh water produces from high salinity solutions, many ways used for this purpose and one of the most important processes is membrane distillation (MD). Direct contact membrane distillation (DCMD) can be considered as the most prominent type from MD types according to ease of design and modus operandi. This work studies the efficiency of using DCMD operation for desalination brine with different concentration (1.75, 3.5, 5 wt. % NaCl). Frame and plate cell was used with flat sheet PTFE hydrophobic type membrane. The study proves that MD is an effective process for desalination brines with feed temperature less than 60˚C especially for feed with low TDS. 37˚C, 47˚C, and 57˚C was feed temperature and 17, 22, 27˚C as permeate temperatures used in study, temperature in both sides of membrane are recorded and TDS for permeate collected to assure that there is no penetration of brine to permeate side, the results took every 30 min for time experiment of 180 min. From results, the flux increases with increasing feed temperature and flow rate, and decreasing with increasing feed concentration, experiment time, and permeate temperature.     

Experimental and Numerical Study of Water Distillation Performance of Small-Scale Direct Contact Membrane Distillation System

2017 ◽  
Author(s):  
Danielle Park ◽  
Elnaz Norouzi ◽  
Chanwoo Park
Keyword(s):  
Water Temperature ◽  
Direct Contact ◽  
Membrane Distillation ◽  
Small Scale ◽  
Feed Water ◽  
Water Production ◽  
Water Distillation ◽  
Direct Contact Membrane Distillation ◽  
Feed Temperature ◽  
Feed Water Temperature

A small-scale Direct Contact Membrane Distillation (DCMD) system was built to investigate its water distillation performance for varying inlet temperatures and flow rates of feed and permeate streams, and salinity. A counterflow configuration between the feed and permeate streams was used to achieve an efficient heat exchange. A two-dimensional Computational Fluid Dynamics (CFD) model was developed and validated using the experimental results. The numerical results were compared with the experiments and found to be in good agreement. From this study, the most desirable conditions for distilled water production were found to be a higher feed water temperature, lower permeate temperature, higher flow rate and less salinity. The feed water temperature had a greater impact on the water production than the permeate water temperature. The numerical simulation showed that the water mass flux was maximum at the inlet of the feed stream where the feed temperature was the highest and rapidly decreased as the feed temperature decreased.

Performance evaluation of ePTFE and PVDF flat-sheet module direct contact membrane distillation

2010 ◽  
Vol 62 (2) ◽  
pp. 347-352 ◽  
Author(s):  
Ching-Jung Chuang ◽  
Kuo-Lun Tung ◽  
Yang-Hsiang Fan ◽  
Chii-Dong Ho ◽  
James Huang
Keyword(s):  
Direct Contact ◽  
Polyvinylidene Fluoride ◽  
Membrane Distillation ◽  
Membrane Properties ◽  
Energy Integration ◽  
Permeate Flux ◽  
Increase Energy Efficiency ◽  
Module Design ◽  
Direct Contact Membrane Distillation ◽  
Flat Sheet

This paper reports experiments using a flat-sheet module with 0.18 ∼ 0.45 μm ePTFE (expanded polytetrafluoroethylene) and PVDF (polyvinylidene fluoride) membranes to show the effects of membrane properties, salt concentration and fluid hydrodynamics on the permeate flux and salt rejection of DCMD (direct contact membrane distillation). A theoretical prediction of the permeate flux was carried out, and was in close agreement with the experimental results. In addition, the energy integration of the process was also analyzed in order to evaluate module design to increase energy efficiency. According to the simulated results of the energy integration design, a combination of simultaneous cooling of the permeate stream and an additional heat exchanger to lower the temperature of the permeate stream not only enhances the MD flux, but also reduces energy consumption.

Reverse osmosis brine treatment using direct contact membrane distillation: Effects of feed temperature and velocity

Desalination ◽  
2017 ◽  
Vol 423 ◽  
pp. 149-156 ◽  
Author(s):  
Zhongsen Yan ◽  
Haiyang Yang ◽  
Fangshu Qu ◽  
Huarong Yu ◽  
Heng Liang ◽  
...  
Keyword(s):  
Reverse Osmosis ◽  
Direct Contact ◽  
Membrane Distillation ◽  
Direct Contact Membrane Distillation ◽  
Brine Treatment ◽  
Feed Temperature

scholarly journals Porous Hydrophobic–Hydrophilic Composite Hollow Fiber and Flat Membranes Prepared by Plasma Polymerization for Direct Contact Membrane Distillation

Membranes ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 120 ◽  
Author(s):  
Ashok K. Sharma ◽  
Adam Juelfs ◽  
Connor Colling ◽  
Saket Sharma ◽  
Stephen P. Conover ◽  
...  
Keyword(s):  
Hollow Fiber ◽  
Direct Contact ◽  
Plasma Polymerization ◽  
Polyvinylidene Fluoride ◽  
Hydrophobic Surface ◽  
Diffusion Path ◽  
High Water ◽  
Membrane Distillation ◽  
Vapor Flux ◽  
Direct Contact Membrane Distillation

High water vapor flux at low brine temperatures without surface fouling is needed in membrane distillation-based desalination. Brine crossflow over surface-modified hydrophobic hollow fiber membranes (HFMs) yielded fouling-free operation with supersaturated solutions of scaling salts and their precipitates. Surface modification involved an ultrathin porous polyfluorosiloxane or polysiloxane coating deposited on the outside of porous polypropylene (PP) HFMs by plasma polymerization. The outside of hydrophilic MicroPES HFMs of polyethersulfone was also coated by an ultrathin coating of porous plasma-polymerized polyfluorosiloxane or polysiloxane rendering the surface hydrophobic. Direct contact membrane distillation-based desalination performances of these HFMs were determined and compared with porous PP-based HFMs. Salt concentrations of 1, 10, and 20 wt% were used. Leak rates were determined at low pressures. Surface and cross-sections of two kinds of coated HFMs were investigated by scanning electron microscopy. The HFMs based on water-wetted MicroPES substrate offered a very thin gas gap in the hydrophobic surface coating yielding a high flux of 26.4–27.6 kg/m2-h with 1 wt% feed brine at 70 °C. The fluxes of HFMs on porous PP substrates having a long vapor diffusion path were significantly lower. Coated HFM performances have been compared with flat hydrophilic membranes of polyvinylidene fluoride having a similar plasma-polymerized hydrophobic polyfluorosiloxane coating.

scholarly journals Simulation of direct contact membrane distillation regeneration of liquid desiccant solutions used in air-conditioning

2020 ◽  
Vol 58 (6) ◽  
pp. 747
Author(s):  
Hung Cong Duong ◽  
Lan Thi Thu Tran
Keyword(s):  
Direct Contact ◽  
Air Conditioning ◽  
Water Flux ◽  
Experimental Tests ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Membrane Properties ◽  
Experimental Investigations ◽  
Liquid Desiccant ◽  
Direct Contact Membrane Distillation

Membrane distillation (MD) has great potential for the treatment of hyper saline waters, including liquid desiccant solutions used in air-conditioning systems. Previous experimental investigations have demonstrated the technical feasibility of MD for regeneration of liquid desiccant solutions. In this study, a direct contact membrane distillation (DCMD) process of the LiCl liquid desiccant solution was simulated using MATLAB software. The simulation was first validated using data obtained from experimental tests. Then, it was used to elucidate the water temperatures, LiCl concentration, and water flux profiles along the membrane leaf inside the DCMD membrane module. Finally, with the help of the simulation, the effects of membrane properties and process operating conditions on the DCMD process performance were systematically examined. The results obtained from this simulation enrich the knowledge and hence facilitate the realization of MD for the liquid desiccant solution regeneration application.

Sign in / Sign up

Export Citation Format

Share Document