scholarly journals Multiphysics Modeling and Analysis of a Solar Desalination Process Based on Vacuum Membrane Distillation

Membranes ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 386
Author(s):  
Benjamin N. Shuldes ◽  
Mona Bavarian ◽  
Siamak Nejati
Keyword(s):  
Salt Concentration ◽  
Saturation Pressure ◽  
Membrane Distillation ◽  
Exergy Efficiency ◽  
Operating Conditions ◽  
Recovery Ratio ◽  
Permeate Flux ◽  
Element Analysis ◽  
Vacuum Membrane Distillation ◽  
Polarization Phenomena

A hollow fiber vacuum membrane distillation (VMD) module was modeled using finite element analysis, and the results were used to conduct an exergy efficiency analysis for a solar-thermal desalination scheme. The performance of the VMD module was simulated under various operating conditions and membrane parameters. Membrane porosity, tortuosity, pore diameter, thickness, and fiber length were varied, along with feed temperature and feed configuration. In all cases, polarization phenomena were seen to inhibit the performance of the module. Under VMD operation, polarization of salt concentration was seen to be the main determining factor in the reduction of permeate flux. Within the boundary layer, salt concentration was seen to rapidly increase from the feed mass fraction of 0.035 to the saturation point. The increase in salt concentration led to a decrease in saturation pressure, the driving force for separation. Charging the feed into the shell instead of the lumen side of the membranes resulted in a further decrease in permeate flux. It is shown that adding a baffling scheme to the surface of the fibers can effectively reduce polarization phenomena and improve permeate flux. Increasing the overall recovery ratio was seen to increase the exergy efficiency of the system. Exergy efficiency was seen to have almost no dependency on membrane parameters due to the low recovery ratio in a single pass and the high heating duty required to reach the desired temperature for the feed stream.

scholarly journals Assessing the Impact of Operating Conditions on the Energy and Exergy Efficiency for Multi-Effect Vacuum Membrane Distillation Systems

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1500
Author(s):  
A. Najib ◽  
J. Orfi ◽  
H. Alansary ◽  
E. Ali
Keyword(s):  
Energy Consumption ◽  
Pilot Plant ◽  
Membrane Distillation ◽  
Exergy Efficiency ◽  
Operating Conditions ◽  
Performance Ratio ◽  
Cold Temperatures ◽  
Energy And Exergy ◽  
Vacuum Membrane Distillation ◽  
The Impact

A comprehensive study was conducted to elucidate the effect of operating conditions on the performance of a multi-effect vacuum membrane distillation pilot plant. A theoretical assessment of the energy and exergy efficiency of the process was achieved using a mathematical model based on heat and mass transfer, which was calibrated using experimental data obtained from the pilot plant. The pilot plant was a solar vacuum multi-effect membrane distillation (V-MEMD) module comprising five stages. It was found that a maximal permeate mass flux of 17.2 kg/m2·h, a recovery ratio of 47.6%, and a performance ratio of 5.38% may be achieved. The resulting gain output ratio (GOR) under these conditions was 5.05, which is comparable to previously reported values. Furthermore, the present work systematically evaluated not only the specific thermal energy consumption (STEC), but also the specific electrical energy consumption (SEEC), which has been generally neglected in previous studies. We show that STEC and SEEC may reach 166 kWh/m3 and 4.5 kWh/m3, respectively. We also observed that increasing the feed flow rate has a positive impact on the process performance, particularly when the feed temperature is higher than 65 °C. Under ideal operational conditions, the exergetic efficiency reached 21.1%, and the maximum fraction of exergy destruction was localized in the condenser compartment. Variation of the inlet hot and cold temperatures at a constant differential showed an interesting and variable impact on the performance indicators of the V-MEMD unit. The difference with the lowest inlet temperatures exhibited the most negative impact on the system performance.

scholarly journals Performance Investigation of O-Ring Vacuum Membrane Distillation Module for Water Desalination

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Adnan Alhathal Alanezi ◽  
H. Abdallah ◽  
E. El-Zanati ◽  
Adnan Ahmad ◽  
Adel O. Sharif
Keyword(s):  
Flow Rate ◽  
Membrane Distillation ◽  
Membrane Module ◽  
Water Desalination ◽  
Feed Flow Rate ◽  
Permeate Flux ◽  
Vacuum Degree ◽  
Flat Sheet ◽  
Vacuum Membrane Distillation ◽  
Feed Temperature

A new O-ring flat sheet membrane module design was used to investigate the performance of Vacuum Membrane Distillation (VMD) for water desalination using two commercial polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) flat sheet hydrophobic membranes. The design of the membrane module proved its applicability for achieving a high heat transfer coefficient of the order of 103 (W/m2 K) and a high Reynolds number (Re). VMD experiments were conducted to measure the heat and mass transfer coefficients within the membrane module. The effects of the process parameters, such as the feed temperature, feed flow rate, vacuum degree, and feed concentration, on the permeate flux have been investigated. The feed temperature, feed flow rate, and vacuum degree play an important role in enhancing the performance of the VMD process; therefore, optimizing all of these parameters is the best way to achieve a high permeate flux. The PTFE membrane showed better performance than the PVDF membrane in VMD desalination. The obtained water flux is relatively high compared to that reported in the literature, reaching 43.8 and 52.6 (kg/m2 h) for PVDF and PTFE, respectively. The salt rejection of NaCl was higher than 99% for both membranes.

A review on membrane applications and transport mechanisms in vacuum membrane distillation

2017 ◽  
Vol 34 (1) ◽  
Author(s):  
Rakesh Baghel ◽  
Sushant Upadhyaya ◽  
Kailash Singh ◽  
Satyendra P. Chaurasia ◽  
Akhilendra B. Gupta ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Membrane Separation ◽  
Critical Evaluation ◽  
Experimental Studies ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
Separation Processes ◽  
Vacuum Membrane Distillation ◽  
Polarization Coefficient ◽  
The Impact

AbstractThe main aim of this article is to provide a state-of-the-art review of the experimental studies on vacuum membrane distillation (VMD) process. An introduction to the history of VMD is carried out along with the other membrane distillation configurations. Recent developments in process, characterization of membrane, module design, transport phenomena, and effect of operating parameters on permeate flux are discussed for VMD in detail. Several heat and mass transfer correlations obtained by various researchers for different VMD modules have been discussed. The impact of membrane fouling with its control in VMD is discussed in detail. In this paper, temperature polarization coefficient and concentration polarization coefficient are elaborated in detail. Integration of VMD with other membrane separation processes/industrial processes have been explained to improve the performance of the system and make it more energy efficient. A critical evaluation of the VMD literature is incorporated throughout this review.

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 Evaluation of Permeate Quality in Pilot Scale Membrane Distillation Systems

Membranes ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 69 ◽  
Author(s):  
Alba Ruiz-Aguirre ◽  
Juan A. Andrés-Mañas ◽  
Guillermo Zaragoza
Keyword(s):  
Surface Membrane ◽  
Pilot Scale ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Distilled Water ◽  
Permeate Flux ◽  
Membrane Area ◽  
Intermittent Operation ◽  
In The Beginning ◽  
Membrane Level

In this work, the salinity of permeate obtained with membrane distillation (MD) in pilot scale systems was analyzed. Experiments were performed with three different spiral-wound commercial modules, one from Solar Spring with 10 m2 surface membrane area and two from Aquastill with 7.2 and 24 m2. Intermittent operation meant that high permeate conductivity was measured in the beginning of each experiment, which was gradually decreasing until reaching a constant value (3–143 µS·cm−1 for seawater feed). The final quality reached did not depend on operating conditions, only the time it took to reach it. This can be because the permeate flux dilutes the minimal feed leak taking place through pinholes in the membranes. Larger feed leak through the membrane was observed when operating in vacuum-enhanced air-gap MD configuration (V-AGMD), which is compatible with this explanation. However, for the increase of feed leak with salinity (up to 1.8 M), a conclusive explanation cannot be given. Pore wetting due to crystallization is discarded because the high permeate quality was recovered after washing with distilled water. More studies at higher salinities and also at membrane level are required to investigate this.

Vacuum membrane distillation for seawater desalination: could it compete with reverse osmosis?

2003 ◽  
Vol 3 (5-6) ◽  
pp. 57-66 ◽  
Author(s):  
D. Wirth ◽  
C. Cabassud
Keyword(s):  
Energy Consumption ◽  
Reverse Osmosis ◽  
Membrane Distillation ◽  
Hollow Fibre ◽  
Permeate Flux ◽  
Seawater Desalination ◽  
Industrial Plants ◽  
Low Energy Consumption ◽  
In Series ◽  
Vacuum Membrane Distillation

This work addresses the potentialities of vacuum membrane distillation (VMD) using hollow fibre membranes for seawater desalination. Experiments were carried out with a synthetic salty water containing a concentration of NaCl from 0 up to 300 g/L. A Microza (Pall) hollow fibre module was used. Experimental results show that, for this module, concentration polarisation and heat transfer limitations are not significant and do not modify the permeate flux. This is a great advantage over reverse osmosis (RO). Energy consumption was then studied using computations based on modelling. Two different industrial plants were considered: the first one consisted of hollow fibre modules arranged in series and operated in a single-pass. The second one was designed for a discontinuous operation using a circulation loop. Computations clearly show the interest (low energy consumption) of VMD for seawater desalination in comparison with RO.

Permeate Flux Curve Characteristics Analysis of Cross-Flow Vacuum Membrane Distillation

2011 ◽  
Vol 51 (1) ◽  
pp. 487-494 ◽  
Author(s):  
Hongtao Wang ◽  
Baoan Li ◽  
Li Wang ◽  
Shasha Song ◽  
Jixiao Wang ◽  
...  
Keyword(s):  
Cross Flow ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
Characteristics Analysis ◽  
Vacuum Membrane Distillation ◽  
Flux Curve

scholarly journals Performance Analysis of a RED-MED Salinity Gradient Heat Engine

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3385 ◽  
Author(s):  
Patricia Palenzuela ◽  
Marina Micari ◽  
Bartolomé Ortega-Delgado ◽  
Francesco Giacalone ◽  
Guillermo Zaragoza ◽  
...  
Keyword(s):  
Performance Analysis ◽  
Power Density ◽  
Waste Heat ◽  
Salinity Gradient ◽  
Heat Engine ◽  
Exergy Efficiency ◽  
Integrated System ◽  
Operating Conditions ◽  
Membrane Properties ◽  
Recovery Ratio

A performance analysis of a salinity gradient heat engine (SGP-HE) is presented for the conversion of low temperature heat into power via a closed-loop Reverse Electrodialysis (RED) coupled with Multi-Effect Distillation (MED). Mathematical models for the RED and MED systems have been purposely developed in order to investigate the performance of both processes and have been then coupled to analyze the efficiency of the overall integrated system. The influence of the main operating conditions (i.e., solutions concentration and velocity) has been quantified, looking at the power density and conversion efficiency of the RED unit, MED Specific Thermal Consumption (STC) and at the overall system exergy efficiency. Results show how the membrane properties (i.e., electrical resistance, permselectivity, water and salt permeability) dramatically affect the performance of the RED process. In particular, the power density achievable using membranes with optimized features (ideal membranes) can be more than three times higher than that obtained with current reference ion exchange membranes. On the other hand, MED STC is strongly influenced by the available waste heat temperature, feed salinity and recovery ratio to be achieved. Lowest values of STC below 25 kWh/m3 can be reached at 100 °C and 27 effects. Increasing the feed salinity also increases the STC, while an increase in the recovery ratio is beneficial for the thermal efficiency of the system. For the integrated system, a more complex influence of operating parameters has been found, leading to the identification of some favorable operating conditions in which exergy efficiency close to 7% (1.4% thermal) can be achieved for the case of current membranes, and up to almost 31% (6.6% thermal) assuming ideal membrane properties.

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