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.

Morphological Study of Fabricated PVDF Based Hydrophobic Membrane for Different Additives and Coagulation Bath Temperature

2021 ◽  
Vol 18 (3) ◽  
pp. 39-47
Author(s):  
Meenakshi Yadav ◽  
Sushant Upadhyaya ◽  
Kailash Singh ◽  
Manish Vashishtha
Keyword(s):  
Contact Angle ◽  
Water Content ◽  
Temperature Difference ◽  
Synergistic Effects ◽  
Weight Percent ◽  
Membrane Distillation ◽  
Coagulation Bath ◽  
Hydrophobic Membrane ◽  
Sem Micrograph ◽  
Dope Solution

The demand of membrane distillation (MD) has increased since last few decades for numerous applications. The membrane used in MD is hydrophobic; therefore, the focus has been emphasised on the development of a suitable membrane with desired microstructure. In this study, the flat sheet hydrophobic membrane of suitable properties has been casted with various additives such as water, ethane-di-ol, and propan-2-ol in dope solution using a non-solvent induced phase separation (NIPS) technique. The effect of water content in dope solution has been studied on casted membrane porosity and contact angle. The maximum contact angle and porosity were found to be 96° and 53.23% at 4 weight percent of water content in dope solution of PVDF polymer and di.methyl.acetamide as solvent. It was found that SEM micrograph when ethane-di-ol and propan-2-ol are used as an additive shows more finger-like pores and nodules, respectively, in the microstructure of the casted membrane. Furthermore, synergistic effects using water with other additives were also identified using SEM micrograph of casted membrane and it was observed that water with ethane-di-ol and propan-2-ol form contact angle of 98° and 105°, respectively, for 2 weight percent each additive in dope. In this study, the membrane was also cast by dissolving PVDF powder in di.methyl.acetamide solvent with lithium chloride and the effect of the temperature difference between coagulation bath and film temperature was investigated using an SEM micrograph. Overall, it was found that water content and temperature difference aid in developing hydrophobic porous membrane of desired properties for MD applications.

Enhancement of Gripping Efficiency of Miniature Gripper Applying Elastic Buckling Phenomenon by Constraining Deformation

2008 ◽  
Author(s):  
H. Ando ◽  
Y. Takami ◽  
N. Muramatsu
Keyword(s):  
Elastic Deformation ◽  
Driving Force ◽  
Experimental Results ◽  
Elastic Buckling ◽  
Trade Off ◽  
Gripping Force

This paper discusses the enhancement of gripping efficiency of a gripping mechanism for miniature grippers. This gripping mechanism employs a displacement enlarging mechanism utilizing an elastic buckling of the flexible gripping fingers. Miniature grippers have been realized by the flexible gripping fingers acting as the displacement enlarging mechanism. However, there is a trade-off relation between the enlarged displacement and gripping force of the gripping mechanism. For this reason, the enhancement of gripping efficiency of the gripping mechanism has been experimentally attempted by constraining an elastic deformation of the flexible gripping fingers. The flexible gripping fingers are largely deformed due to elastic buckling after gripping an object. This elastic deformation is constrained by supports. Experiments have been conducted for some different cases of placement of the supports. The driving force, driving displacement and gripping force of the gripping mechanism have been measured. From experimental results, it has been confirmed that the enhancement of gripping efficiency of the gripping mechanism is feasible by controlling deformation of the flexible fingers passively.

scholarly journals Redox flow desalination based on the temperature difference as a driving force

2020 ◽  
pp. 127716
Author(s):  
Jinhong Dai ◽  
Mingzhi Huang ◽  
Kwan San Hui ◽  
Denis Y.W. Yu ◽  
Dongliang Yan ◽  
...  
Keyword(s):  
Temperature Difference ◽  
Driving Force

scholarly journals Interplay of the Factors Affecting Water Flux and Salt Rejection in Membrane Distillation: A State-of-the-Art Critical Review

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2841
Author(s):  
Lin Chen ◽  
Pei Xu ◽  
Huiyao Wang
Keyword(s):  
Water Flux ◽  
Feed Solution ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Membrane Properties ◽  
Membrane Thickness ◽  
Membrane Pore ◽  
Factors Affecting ◽  
Term Operation ◽  
Salt Rejection

High water flux and elevated rejection of salts and contaminants are two primary goals for membrane distillation (MD). It is imperative to study the factors affecting water flux and solute transport in MD, the fundamental mechanisms, and practical applications to improve system performance. In this review, we analyzed in-depth the effects of membrane characteristics (e.g., membrane pore size and distribution, porosity, tortuosity, membrane thickness, hydrophobicity, and liquid entry pressure), feed solution composition (e.g., salts, non-volatile and volatile organics, surfactants such as non-ionic and ionic types, trace organic compounds, natural organic matter, and viscosity), and operating conditions (e.g., temperature, flow velocity, and membrane degradation during long-term operation). Intrinsic interactions between the feed solution and the membrane due to hydrophobic interaction and/or electro-interaction (electro-repulsion and adsorption on membrane surface) were also discussed. The interplay among the factors was developed to qualitatively predict water flux and salt rejection considering feed solution, membrane properties, and operating conditions. This review provides a structured understanding of the intrinsic mechanisms of the factors affecting mass transport, heat transfer, and salt rejection in MD and the intra-relationship between these factors from a systematic perspective.

Sampling rainfall events: a novel approach to generate large correlated samples

2012 ◽  
Vol 44 (2) ◽  
pp. 351-361 ◽  
Author(s):  
Siao Sun ◽  
Soon-Thiam Khu ◽  
Slobodan Djordjević
Keyword(s):  
Computational Efficiency ◽  
Driving Force ◽  
Group Method ◽  
Marginal Distributions ◽  
Rainfall Events ◽  
Trade Off ◽  
Large Group ◽  
Efficient Generation ◽  
Novel Approach ◽  
Novel Method

It is essential that the correlation between variables is considered properly when using sampling-based methods. Modeling rainfall events is of great interest because the rainfall is usually the major driving force of hydrosystems. A novel method for generating correlated samples is introduced providing that the marginal distributions of variables as well as their correlations between them are known. The basic idea of the method is to adjust the correlations between samples by rearranging the positions inside marginal samples after each marginal sample is generated according to its distribution. The group method is developed in order to facilitate an efficient generation of correlated samples of large sizes. The theoretical precision associated with the group method is derived. There is a trade off between the computational efficiency of the algorithm and the precision that can be achieved when using different numbers of groups. The method is successfully applied to two cases of rainfall sample generation problems. The effectiveness of the group method is studied. Large group numbers are recommended in practical use as the samples distribute more broadly regardless of computational efficiency.

Impact of a biofouling layer on the vapor pressure driving force and performance of a membrane distillation process

2013 ◽  
Vol 438 ◽  
pp. 140-152 ◽  
Author(s):  
Shuwen Goh ◽  
Qiaoyun Zhang ◽  
Jinsong Zhang ◽  
Diane McDougald ◽  
William B. Krantz ◽  
...  
Keyword(s):  
Vapor Pressure ◽  
Driving Force ◽  
Membrane Distillation ◽  
Distillation Process ◽  
And Performance

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.

scholarly journals Membrane distillation crystallization using PVDF membrane incorporated with TiO2 nanoparticles and nanocellulose

2020 ◽  
Vol 20 (5) ◽  
pp. 1629-1642 ◽  
Author(s):  
Hoi-Fang Tan ◽  
Why-Ling Tan ◽  
N. Hamzah ◽  
M. H. K. Ng ◽  
B. S. Ooi ◽  
...  
Keyword(s):  
Pore Size ◽  
Tio2 Nanoparticles ◽  
Polyvinylidene Fluoride ◽  
Phase Inversion ◽  
Membrane Distillation ◽  
Coagulation Bath ◽  
Membrane Thickness ◽  
Permeate Flux ◽  
Sem Images ◽  
Pvdf Membrane

Abstract Polyvinylidene fluoride (PVDF) membrane was improved using TiO2 nanoparticles and nanocellulose for membrane distillation crystallization in this work. Besides the addition of TiO2 nanoparticles and nanocellulose, PVDF membrane was post-modified with octadecyltrichlorosilane after phase inversion using a dual coagulation bath. The addition of hydrophilic TiO2 nanoparticles and nanocellulose reduced membrane hydrophobicity, but the dispersed TiO2 nanoparticles assisted silane modification to improve surface hydrophobicity. Besides reducing the agglomeration of TiO2 nanoparticles, nanocellulose induced the formation of larger pore size and higher porosity as proven in SEM images and gravimetric measurement, respectively. The abundant moieties of nanocellulose accelerated the exchange between solvent and non-solvent during phase inversion for the formation of large pore size and porosity, but membrane thickness increased due to the thickening effects. The modified membrane showed higher water permeate flux in membrane distillation with salt rejection greater than 97%. Severe fouling in membrane distillation crystallization was not observed.

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

Driving force and activation energy in air-gap membrane distillation process

2015 ◽  
Vol 69 (11) ◽  
Author(s):  
Joanna Kujawa ◽  
Wojciech Kujawski
Keyword(s):  
Activation Energy ◽  
Transport Properties ◽  
Driving Force ◽  
Membrane Distillation ◽  
Air Gap ◽  
Water Fluxes ◽  
Distillation Process ◽  
Air Gap Membrane Distillation ◽  
Different Temperatures ◽  
The Impact

AbstractThe present study investigated the impact of the driving force (Δp) on the transport properties. All the experiments and calculations were performed for air-gap membrane distillation (AGMD). In the course of the experiments, it was found that an identical value of Δp could be attained by applying different values of feed and permeate temperatures. It was highlighted that constant values of water fluxes could be achieved using the constant driving force created by different temperatures. Moreover, the relation between ln(J

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