Heat and Mass Transfer Characteristics of Vapor Permeation in Sweeping Gas Membrane Distillation Systems for Sea Water Desalination

2019 ◽  
Author(s):  
Umar F. Alqsair ◽  
Anas M. Alwatban ◽  
Abdullah A. Alghafis ◽  
Ahmed M. Alshwairekh ◽  
Alparslan Oztekin
Keyword(s):  
Sea Water ◽  
Three Dimensional ◽  
Concentration Field ◽  
Membrane Distillation ◽  
Water Desalination ◽  
Membrane Properties ◽  
Membrane Thickness ◽  
Temperature Polarization ◽  
Dynamics Simulations ◽  
Sweeping Gas

Abstract Computational fluid dynamics simulations are conducted to study the performance of the sweeping gas membrane distillation module (SGMD) for seawater desalination process. The main objective of this work is to study the effect of membrane properties on the membrane flux performance and temperature and concentration polarization characteristics of the module. 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 are set to 900 and 2000, and thus the laminar flow model is adapted for each channel. The effects of the porosity and the membrane thickness are varied while the pore size is fixed for the parametric study. It is revealed that the membrane thickness has a profound influence while the membrane porosity has a slight influence on the SGMD performance. We observed a high level of temperature polarization within the module, which adversely affects the system performance. Remedies for mitigating temperature polarization should be considered for future studies.

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.

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 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.

Experiments on sea water desalination by membrane distillation

Desalination ◽  
1990 ◽  
Vol 78 (2) ◽  
pp. 177-185 ◽  
Author(s):  
K. Ohta ◽  
K. Kikuchi ◽  
I. Hayano ◽  
T. Okabe ◽  
T. Goto ◽  
...  
Keyword(s):  
Sea Water ◽  
Membrane Distillation ◽  
Water Desalination

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 CFD Investigation of Spacer-Filled Channels for Membrane Distillation

Membranes ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 91
Author(s):  
Mariagiorgia La Cerva ◽  
Andrea Cipollina ◽  
Michele Ciofalo ◽  
Mohammed Albeirutty ◽  
Nedim Turkmen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Reynolds Numbers ◽  
Membrane Distillation ◽  
Water Desalination ◽  
Process Models ◽  
Process Efficiency ◽  
Pressure Drops ◽  
Temperature Polarization

The membrane distillation (MD) process for water desalination is affected by temperature polarization, which reduces the driving force and the efficiency of the process. To counteract this phenomenon, spacer-filled channels are used, which enhance mixing and heat transfer but also cause higher pressure drops. Therefore, in the design of MD modules, the choice of the spacer is crucial for process efficiency. In the present work, different overlapped spacers are investigated by computational fluid dynamics (CFD) and results are compared with experiments carried out with thermochromic liquid crystals (TLC). Results are reported for different flow attack angles and for Reynolds numbers (Re) ranging from ~200 to ~800. A good qualitative agreement between simulations and experiments can be observed for the areal distribution of the normalized heat transfer coefficient. Trends of the average heat transfer coefficient are reported as functions of Re for the geometries investigated, thus providing the basis for CFD-based correlations to be used in higher-scale process models.

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 Pressure-Temperature Limit Curve of System-Integrated Modular Advanced Reactor Against Nonductile Failure

2007 ◽  
Author(s):  
Yoon-Suk Chang ◽  
Hyuk-Soo Chang ◽  
Sang-Min Lee ◽  
Jae-Boong Choi ◽  
Young-Jin Kim ◽  
...  
Keyword(s):  
Temperature Change ◽  
Sea Water ◽  
Three Dimensional ◽  
Design Procedure ◽  
Temperature Limit ◽  
Water Desalination ◽  
Electricity Production ◽  
Limit Curve ◽  
Crack Location ◽  
Three Dimensional Finite Element

A system-integrated modular advanced reactor is being developed for multi purposes such as electricity production, sea water desalination and so on in Korea. While ASME Codes provide simplified design and operation procedures to determine allowable loadings for pressure retaining materials in components, the procedures are applicable when a temperature change rate associated with startup and shutdown is less than about 56°C/hr. If the procedures are applied to a rapid temperature change, results would be overly conservative. The objective of this research is to assess an applicability of the simplified design procedures to reactor coolant system of the integrated modular reactor with the change rates of 56°C/hr and 100°C/hr. To investigate effects of cooldown rate, heatup rate and surface crack location, systematic three-dimensional finite element analyses are carried out. The resulting pressure-temperature limit curves are compared with those obtained from the ASME Sec. XI operating procedure as well as Sec. III design procedure. Thereby, it was proven that the specific design features significantly affect the safe design region in the pressure-temperature limit curve to prevent a nonductile failure.

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