Experimental Study and Numerical Simulation of the Air Gap Membrane Distillation (AGMD) Process

2016 ◽  
Vol 11 (1) ◽  
pp. 41-45 ◽  
Author(s):  
Ehsan Karbasi ◽  
Javad Karimi-Sabet ◽  
J. Mohammadi Roshandeh ◽  
M. A. Moosavian ◽  
H. Ahadi
Keyword(s):  
Numerical Simulation ◽  
Membrane Surface ◽  
Membrane Distillation ◽  
Air Gap ◽  
Operating Conditions ◽  
Permeate Flux ◽  
Air Gap Membrane Distillation ◽  
Temperature Polarization ◽  
Output Ratio ◽  
Cfd Method

Abstract Some challenges, including inappropriate distribution of currents on the membrane surface, poor hydrodynamics and existing severe temperature polarization (TP) phenomenon in MD modules, impede industrialization of MD process. Computational fluid dynamics (CFD) method was used for numerical simulation of hydrodynamics in air gap membrane distillation modules. One of two simulated modules in this work is a novel developed one in which heat and mass transfer data was compared with available literature data. Moreover, the effect of using baffles in module was investigated. Comparison between the novel module and conventional module indicates higher trans-membrane mass flux and gained output ratio (GOR) coefficient by 7% and 15%, respectively. Moreover, the effects of different operating conditions including feed temperatures and feed flow rates on permeate flux were investigated.

scholarly journals Bispacer Multi-Stage Direct Contact Membrane Distillation System: Analytical and Experimental Study

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1297
Author(s):  
Morteza Aliabadi ◽  
Hassan Ghorashi ◽  
Shamim Shokri Motlagh ◽  
Seyedeh Fatemeh Nabavi ◽  
Seyed Arash Pakzad ◽  
...  
Keyword(s):  
Direct Contact ◽  
Mechanical Stability ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Permeate Flux ◽  
Direct Contact Membrane Distillation ◽  
Multi Stage ◽  
Temperature Polarization ◽  
Output Ratio ◽  
Polarization Coefficient

A multi-staged direct contact membrane distillation (MDCMD) system is designed considering a novel bispacer configuration in the present study. The proposed bispacer DCMD, which has not been addressed in the literature to best of our knowledge, is considered with two purposes, including increasing mechanical stability and turbulence. As increasing turbulence leads to increasing Nusselt number, the bispacer MDCMD provides higher permeate flux. An analytical approach is considered using energy and mass balance correlation. The effect of bispacer and feed operating conditions, including feed temperature, feed flow rate, feed salinity, and the number of stages on permeate flux and salt rejection of the developed MDCMD, are examined both analytically and experimentally. The performance and sustainability of the developed system were investigated by analyzing the parameters, including thermal efficiency (η), gained output ratio (GOR), and temperature polarization coefficient (TPC).

scholarly journals Enhancement of the air gap membrane distillation system performance by using the water gap module

2020 ◽  
Vol 20 (7) ◽  
pp. 2884-2902
Author(s):  
Mostafa Abd El-Rady Abu-Zeid ◽  
Xiaolong Lu ◽  
Shaozhe Zhang
Keyword(s):  
Membrane Distillation ◽  
Air Gap ◽  
Operating Conditions ◽  
Coolant Temperature ◽  
Concentration Boundary ◽  
Air Gap Membrane Distillation ◽  
Distillation System ◽  
Negative Effect ◽  
In Series ◽  
Output Ratio

Abstract The negative effect of an air gap layer presented between the membrane and cooling plate on air gap membrane distillation (AGMD) performance was diminished largely by inserting a water gap membrane distillation (WGMD) module in series. The new design of air-gap–water-gap membrane distillation (AG-WG)MD was evaluated experimentally by comparing with an AGMD system under different operating conditions. In theory, mass and heat transfer in the new (AG-WG)MD and imitative AGMD systems were analyzed. Experimental outcomes showed that a new (AG-WG)MD design profoundly enhanced flux (Pd) and gained output ratio (GOR), and greatly decreased energy consumption (STEC) and heat input (EH.I). At a concentration of 5,000 mg/L, coolant temperature of 20 °C, and flow rate of 18 L/h, Pd was promoted by 76.26%, 40.84%, 35.45%, 30.91%, and GOR by 46.38%, 33.46%, 31.27%, 26.65%, in addition to STEC being reduced about 55.63%, 46.81%, 43.66%, 38.30%, and EH.I around 31.31%, 25.84%, 23.53%, 20.55%, from the AGMD to (AG-WG)MD system at feed temperatures of 50 °C, 60 °C, 70 °C, and 80 °C, respectively. The outcomes proved that the AGMD performance could be significantly promoted by integrating with WGMD in a combined MD system. This combination increased the temperature difference across the membrane and decreased thermal-concentration boundary layers for the AGMD system.

scholarly journals A Comparison Study of Brine Desalination using Direct Contact and Air Gap Membrane Distillation

2019 ◽  
Vol 25 (11) ◽  
pp. 47-54
Author(s):  
Ahmed Shamil Khalaf ◽  
Asrar Abdullah Hassan
Keyword(s):  
Flow Rate ◽  
Direct Contact ◽  
Polyvinylidene Fluoride ◽  
Membrane Distillation ◽  
Air Gap ◽  
Feed Flow Rate ◽  
Permeate Flux ◽  
Air Gap Membrane Distillation ◽  
Flat Sheet ◽  
Feed Temperature

Membrane distillation (MD) is a hopeful desalination technique for brine (salty) water. In this research, Direct Contact Membrane Distillation (DCMD) and  Air Gap Membrane Distillation (AGMD) will be used. The sample used is from Shat Al –Arab water (TDS=2430 mg/l). A polyvinylidene fluoride (PVDF) flat sheet membrane was used as a flat sheet form with a plate and frame cell. Several parameters were studied, such as; operation time, feed temperature, permeate temperature, feed flow rate. The results showed that with time, the flux decreases because of the accumulated fouling and scaling on the membrane surface. Feed temperature and feed flow rate had a positive effect on the permeate flux, while permeate temperature had a reverse effect on permeate flux. It is noticeable that the flux in DCMD is greater than AGMD, at the same conditions. The flux in DCMD is 10.95LMH, and that in AGMD is 7.14 LMH.  In AGMD, the air gap layer made a high resistance. Here the temperature transport reduces in the permeate side of AGMD due to the air gap resistance. The heat needed for AGMD is lower than DCMD, this leads to low permeate flux because the temperature difference between the two sides is very small, so the driving force (vapor pressure) is low.                                                                                               

scholarly journals Performances of air gap and water gap MD desalination modules

2018 ◽  
Vol 13 (1) ◽  
pp. 200-209 ◽  
Author(s):  
Atia E. Khalifa
Keyword(s):  
Specific Energy Consumption ◽  
Membrane Distillation ◽  
Air Gap ◽  
Dominant Factor ◽  
Feed Water ◽  
Permeate Flux ◽  
Hydrophobic Membrane ◽  
Air Gap Membrane Distillation ◽  
Gap Width ◽  
Feed Temperature

Abstract Membrane distillation (MD) is a promising thermally-driven membrane separation technology for water desalination. In MD, water vapor is being separated from the hot feed water solution using a micro-porous hydrophobic membrane, due to the difference in vapor pressures across the membrane. In the present work, experiments are conducted to compare the performance of water gap membrane distillation (WGMD) and air gap membrane distillation (AGMD) modules under the main operating and design conditions including the feed and coolant temperatures, membrane material and pore sizes, and the gap width. Results showed that the WGMD module produced higher fluxes as compared to the AGMD module, for all test conditions. The feed temperature is the dominant factor affecting the system flux. The permeate flux increases with reducing the gap width for both water and air gap modules. However, WGMD module was found to be less sensitive to the change in the gap width compared to the AGMD module. The PTFE membrane produced higher permeate flux as compared to the PVDF membrane. Bigger mean pore diameter enhanced the permeate flux, however, this enhancement is marginal at high feed temperatures. With increasing the feed temperature, the GOR values increase and the specific energy consumption decreases.

scholarly journals Modification of porous polyetherimide hollow fiber membrane by dip-coating of Zonyl® BA for membrane distillation of dyeing wastewater

2021 ◽  
Author(s):  
S. A. Mousavi ◽  
Z. Arab Aboosadi ◽  
A. Mansourizadeh ◽  
B. Honarvar
Keyword(s):  
Pore Size ◽  
Hollow Fiber ◽  
Hollow Fiber Membrane ◽  
Membrane Surface ◽  
Pure Water ◽  
Dip Coating ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
Fiber Membrane ◽  
Air Gap Membrane Distillation

Abstract Wetting and fouling have significantly affected the application of membrane distillation (MD). In this work, a dip-coating method was used for improving surface hydrophobicity of the polyetherimide (PEI) hollow fiber membrane. An air gap membrane distillation (AGMD) process was applied for treatment of the methylene blue (MB) solution. The porous PEI membrane was fabricated by a dry-wet spinning process and the hydrophobic 2-(Perfluoroalkyl) ethanol (Zonyl® BA) was used as the coating material. From FESEM, the modified PEI-Zonyl membrane showed an open structure with large finger-like cavities. The modified membrane displayed a narrow pore size distribution with mean pore size of 0.028 μm. The outer surface contact angle of the PEI-Zonly membrane increased from 81.3° to 100.4° due to the formation of an ultra-thin coated layer. The pure water flux of the PEI-Zonyl membrane was slightly reduced compared to the pristine PEI membrane. The permeate flux of 6.5 kg/m2 h and MB rejection of 98% was found for the PEI-Zonyl membrane during 76 h of the AGMD operation. Adsorption of MB on the membrane surface was confirmed based on the Langmuir isotherm evaluation, AFM and FESM analysis. The modified PEI-Zonyl membrane can be a favorable alternative for AGMD of dyeing wastewaters.

Channel Length Influence on the Performance of the Vacuum Membrane Distillation

2020 ◽  
Author(s):  
Abdulaziz M. Alasiri ◽  
Umar Alqsair ◽  
Sertac Cosman ◽  
Robert Krysko ◽  
Alparslan Oztekin
Keyword(s):  
Membrane Surface ◽  
Membrane Distillation ◽  
Channel Length ◽  
Water Vapor Transport ◽  
Membrane Thickness ◽  
Local Concentration ◽  
Permeate Flux ◽  
Hydrophobic Membrane ◽  
Vapor Flux ◽  
Temperature Polarization

Abstract The demand for freshwater has been increased globally. Membrane distillation (MD) technique can be an attractive option for desalination applications. MD is defined as a thermal-driven separation process that implements a hydrophobic membrane for allowing only water vapor transport through the membrane. VMD system is investigated in this study to examine its sensitivity toward the channel design. PTFE membrane is employed and treated as a functional surface where its main properties, such as porosity, tortuosity, pore diameter, and membrane thickness are defined. Different flow rates and inlet temperatures of the feed solution are involved to intensely study the effect of the channel length on VMD performance. The local concentration and temperature polarization coefficient and mass flux along the membrane surface are presented and discussed. With the increasing length of the module, concentration and temperature polarization levels are increased, and the vapor flux is decreased. It is shown that the permeate flux decreases linearly with the channel length. The slope of the permeate flux with length can be used to estimate the flux performance of modules with varying length.

Permeate flux enhancement with a helical wired concentric tube in air gap membrane distillation systems

2020 ◽  
Vol 201 ◽  
pp. 150-168
Author(s):  
Chii-Dong Ho ◽  
Luke Chen ◽  
Kun-Yi Wu ◽  
Chi-Hsiang Ni ◽  
Thiam Leng Chew
Keyword(s):  
Membrane Distillation ◽  
Air Gap ◽  
Permeate Flux ◽  
Flux Enhancement ◽  
Air Gap Membrane Distillation

Persian Gulf desalination using air gap membrane distillation: Numerical simulation and theoretical study

Desalination ◽  
2015 ◽  
Vol 374 ◽  
pp. 92-100 ◽  
Author(s):  
Morteza Asghari ◽  
Amir Harandizadeh ◽  
Mostafa Dehghani ◽  
Hossein Riasat Harami
Keyword(s):  
Numerical Simulation ◽  
Persian Gulf ◽  
Theoretical Study ◽  
Membrane Distillation ◽  
Air Gap ◽  
Air Gap Membrane Distillation

scholarly journals Mass Transfer Analysis of Air-Cooled Membrane Distillation Configuration for Desalination

Membranes ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 281
Author(s):  
Shuo Cong ◽  
Qingxiu Miao ◽  
Fei Guo
Keyword(s):  
Mass Transfer ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Transfer Model ◽  
Permeate Flux ◽  
Practical Applications ◽  
Conductive Plate ◽  
Air Gap Membrane Distillation ◽  
Two Factors ◽  
Thermally Conductive

It has been proposed that the air-cooled configuration for air gap membrane distillation is an effective way to simplify the system design and energy source requirement. This offers potential for the practical applications of membrane distillation on an industrial scale. In this work, membrane distillation tests were performed using a typical water-cooled membrane distillation (WCMD) configuration and an air-cooled membrane distillation (ACMD) configuration with various condensing plates and operating conditions. To increase the permeate flux of an ACMD system, the condensing plate in the permeate side should transfer heat to the atmosphere more effectively, such as using a more thermally conductive plate, adding fins, or introducing forced convection air flow. Importantly, a practical mass transfer model was proposed to describe the ACMD performance in terms of permeate flux. This model can be simplified by introducing specific correction values to the mass transfer coefficient of a WCMD process under the same conditions. The two factors relate to the capacity (B) and the efficiency (σ), which can be considered as the characteristic factors of a membrane distillation (MD) system. The experimental results are consistent with the theoretical estimations based on this model, which can be used to describe the performance of an MD process.

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