Thermal-exergy efficiency trade-off optimization of pressure retarded membrane distillation based on TOPSIS model

Desalination ◽  
2022 ◽  
Vol 523 ◽  
pp. 115446
Author(s):  
Han Cao ◽  
Yanpeng Mao ◽  
Wenlong Wang ◽  
Yibo Gao ◽  
Miaomiao Zhang ◽  
...  
Keyword(s):  
Membrane Distillation ◽  
Exergy Efficiency ◽  
Trade Off ◽  
Topsis Model

scholarly journals Trade-off in membrane distillation with monolithic omniphobic membranes

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Wei Wang ◽  
Xuewei Du ◽  
Hamed Vahabi ◽  
Song Zhao ◽  
Yiming Yin ◽  
...  
Keyword(s):  
Membrane Distillation ◽  
Trade Off

scholarly journals Analysis of Polyvinylidene Fluoride Membranes Fabricated for Membrane Distillation

Membranes ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 437
Author(s):  
Minchul Ahn ◽  
Hyeongrak Cho ◽  
Yongjun Choi ◽  
Seockheon Lee ◽  
Sangho Lee
Keyword(s):  
Water Vapor ◽  
Polyvinylidene Fluoride ◽  
Water Productivity ◽  
Water Vapor Permeability ◽  
Membrane Distillation ◽  
Inversion Method ◽  
Vapor Permeability ◽  
Trade Off ◽  
Depth Analysis ◽  
Phase Inversion Method

The optimization of the properties for MD membranes is challenging due to the trade-off between water productivity and wetting tendency. Herein, this study presents a novel methodology to examine the properties of MD membranes. Seven polyvinylidene fluoride (PVDF) membranes were synthesized under different conditions by the phase inversion method and characterized to measure flux, rejection, contact angle (CA), liquid entry pressure (LEP), and pore sizes. Then, water vapor permeability (Bw), salt leakage ratio (Lw), and fiber radius (Rf) were calculated for the in-depth analysis. Results showed that the water vapor permeability and salt leakage ratio of the prepared membranes ranged from 7.76 × 10−8 s/m to 20.19 × 10−8 s/m and from 0.0020 to 0.0151, respectively. The Rf calculated using the Purcell model was in the range from 0.598 μm to 1.690 μm. Since the Rf was relatively small, the prepared membranes can have high LEP (more than 1.13 bar) even at low CA (less than 90.8°). The trade-off relations between the water vapor permeability and the other properties could be confirmed from the results of the prepared membranes. Based on these results, the properties of an efficient MD membrane were suggested as a guideline for the membrane development.

Elucidating the Trade-off between Membrane Wetting Resistance and Water Vapor Flux in Membrane Distillation

2020 ◽  
Vol 54 (16) ◽  
pp. 10333-10341 ◽  
Author(s):  
Chenxi Li ◽  
Xuesong Li ◽  
Xuewei Du ◽  
Ying Zhang ◽  
Wei Wang ◽  
...  
Keyword(s):  
Water Vapor ◽  
Membrane Distillation ◽  
Water Vapor Flux ◽  
Trade Off ◽  
Vapor Flux ◽  
Membrane Wetting

scholarly journals Minimum Net Driving Temperature Concept for Membrane Distillation

Membranes ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 100
Author(s):  
Bastiaan Blankert ◽  
Johannes S. Vrouwenvelder ◽  
Geert-Jan Witkamp ◽  
Noreddine Ghaffour
Keyword(s):  
Temperature Difference ◽  
Driving Force ◽  
Membrane Distillation ◽  
Membrane Thickness ◽  
Similar Magnitude ◽  
Trade Off ◽  
Optimal Values ◽  
Single Effect ◽  
Heat Requirement ◽  
Temperature Concept

In this study, we analyzed the heat requirement of membrane distillation (MD) to investigate the trade-off between the evaporation efficiency and driving force efficiency in a single effect MD system. We found that there exists a non-zero net driving temperature difference that maximizes efficiency. This is the minimum net driving temperature difference necessary for a rational operational strategy because below the minimum net driving temperature, both the productivity and efficiency can be increased by increasing the temperature difference. The minimum net driving temperature has a similar magnitude to the boiling point elevation (~0.5 °C for seawater), and depends on the properties of the membrane and the heat exchanger. The minimum net driving temperature difference concept can be used to understand the occurrence of optimal values of other parameters, such as flux, membrane thickness, and membrane length, if these parameters are varied in a way that consequently varies the net driving temperature difference.

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 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.

A Flow-Preserving Algorithm for the Time-Cost Trade-Off Problem

1982 ◽  
Vol 14 (2) ◽  
pp. 109-113 ◽  
Author(s):  
Suleyman Tufekci
Keyword(s):  
Time Cost ◽  
Trade Off

Dual Goals for Speed and Accuracy on the Same Performance Task

2012 ◽  
Vol 11 (3) ◽  
pp. 118-126 ◽  
Author(s):  
Olive Emil Wetter ◽  
Jürgen Wegge ◽  
Klaus Jonas ◽  
Klaus-Helmut Schmidt
Keyword(s):  
Memory Scanning ◽  
Performance Task ◽  
Performance Tasks ◽  
Trade Off ◽  
Test Experiment ◽  
Trade Offs ◽  
New Finding ◽  
Sternberg Paradigm ◽  
Speed Accuracy ◽  
Speed And Accuracy

In most work contexts, several performance goals coexist, and conflicts between them and trade-offs can occur. Our paper is the first to contrast a dual goal for speed and accuracy with a single goal for speed on the same task. The Sternberg paradigm (Experiment 1, n = 57) and the d2 test (Experiment 2, n = 19) were used as performance tasks. Speed measures and errors revealed in both experiments that dual as well as single goals increase performance by enhancing memory scanning. However, the single speed goal triggered a speed-accuracy trade-off, favoring speed over accuracy, whereas this was not the case with the dual goal. In difficult trials, dual goals slowed down scanning processes again so that errors could be prevented. This new finding is particularly relevant for security domains, where both aspects have to be managed simultaneously.

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