Thermal boundary layers in sweeping gas membrane distillation processes

Khayet, M.; Godino, M.P.; Mengual, J.I.

doi:10.1002/aic.690480713

Cited by 74 publications

(53 citation statements)

References 17 publications

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“…After more than a decade, Khayet et al conducted a series of experimental and modelling studies to further explore the influences of operational parameters on the process performance in SGMD [18][19][20][21]. In their work, the temperature profile along the membrane module and the temperature polarization in SGMD were explored by mathematical modelling [19,20]. Recently, both response surface model and artificial neural network have been developed for the prediction and optimization of SGMD processes [22,23].…”

Section: Introductionsupporting

confidence: 39%

“…Work on SGMD was first reported in 1987 and the effects of operational parameters on evaporation efficiency were studied [17]. After more than a decade, Khayet et al conducted a series of experimental and modelling studies to further explore the influences of operational parameters on the process performance in SGMD [18][19][20][21]. In their work, the temperature profile along the membrane module and the temperature polarization in SGMD were explored by mathematical modelling [19,20].…”

Section: Introductionsupporting

confidence: 39%

“…A higher gas flow rate could cause a thinner boundary layer and thus reduces the overall mass transfer resistance. The gas flow rate affects vapor flux also likely by influencing the temperature polarization effect [20], which still occurs at the active layer. Additionally, at higher gas flow rates, the transferred water vapor could be removed out of the module more effectively by lowering the pressure on the gas side via the Bernoulli effect, which will further facilitate the mass transfer across the membrane.…”

Section: Effect Of Gas Flow Rate On Mass Transfer In Sgmdmentioning

confidence: 44%

“…Additionally, vapor flux in SGMD could be related to the humidity change, and the following equation has been used for flux determination [18,20]: (23) where ω g, out and ω g, in are the outlet and inlet gas humidity ratios (g/kg), respectively, and ṁ g is the mass flow rate of the sweeping gas (kg/h). It must be noted that Eq.…”

Section: Vapor Pressure Humidity and Flux Determinationmentioning

confidence: 45%

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Condensation studies in membrane evaporation and sweeping gas membrane distillation

Zhao

Feron

Xie

et al. 2014

Journal of Membrane Science

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Vapor transfer is an important phenomenon in various thermally driven membrane processes such as membrane distillation (MD), membrane evaporation and membrane condensation. In this study, we explore the mass transfer phenomena in sweeping gas membrane distillation (SGMD) by systematically investigating the effects of operational parameters on the process performance. It is found that mass transfer in SGMD is principally determined by both the evaporation temperature and the sweeping gas flow rate, and is significantly influenced by the operational parameters (i.e. fluid velocities) through multiple effects, including the boundary layer effect on both sides of the membrane, and the temperature polarization effect. We also prove that at low gas flow rates (i.e. insufficient gas vapor-holding capacity) the sweeping gas becomes saturated and water vapor forms droplets due to condensation on the gas side of the membrane. To the best of our knowledge, this is the first study reporting the interesting mass transfer phenomena in terms of vapor condensation and droplet re-evaporation in SGMD, which are of great significance for the heat and mass transfer in many thermally driven membrane processes using stripping gas.

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Section: Introductionsupporting

confidence: 39%

Section: Introductionsupporting

confidence: 39%

Section: Effect Of Gas Flow Rate On Mass Transfer In Sgmdmentioning

confidence: 44%

Section: Vapor Pressure Humidity and Flux Determinationmentioning

confidence: 45%

See 2 more Smart Citations

Condensation studies in membrane evaporation and sweeping gas membrane distillation

Zhao

Feron

Xie

et al. 2014

Journal of Membrane Science

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“…The driving force for vapor transport is the vapor pressure difference across the membrane caused by the temperature gradient between the hot-feed and cold-permeate. Among various MD processes, direct contact membrane distillation (DCMD) is the simplest mode because no external condenser is required, compared to vacuum membrane distillation (VMD) and sweep gas membrane distillation (SGMD) [1][2][3][4].…”

Section: Introductionmentioning

confidence: 44%

Performance improvement of PVDF hollow fiber-based membrane distillation process

Yang

Wang

Shi

et al. 2011

Journal of Membrane Science

229

144

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The performance of membrane distillation depends on both membrane and module characteristics. This paper describes strategies to improve the performance of hollow fiber membrane modules used in Direct Contact Membrane Distillation (DCMD).Three different types of hydrophobic polyvinylidene fluoride (PVDF) hollow fiber membrane (unmodified, plasma modified and chemically modified) were used in this study of Direct Contact Membrane Distillation (DCMD). Compared to the unmodified PVDF hollow fiber membrane, both modified membranes showed greater hydrophobicity and mechanical strength, smaller maximum pore sizes and narrower pore size distributions, leading to more sustainable fluxes and higher water quality (distillate conductiviy < 1µs·cm -1 ) over a one month test using synthetic seawater (3.5 wt% sodium chloride solutions).Comparing the plasma and chemical modification the latter has marginally better performance and provides potentially more homogeneous modification.MD modules based on shell and tube configuration were tested to identify the effects of shell and lumen side flow rates, fiber length and packing density. The MD flux increased to an asymptotic value when shell-side Re f was larger than 2500, while the permeate/lumen side reached an asymptotic value at much lower Re p (>300). By comparing the performance of small and larger modules, it was found that it is important to utilize a higher shell-side Re in the operation to maintain a better mixing near the membrane surface in a larger module.Single fiber tests in combination with heat transfer analysis, verified that a critical fiber 3 length existed that is the required length to assure sufficient driving force along the fiber to maintain adequate MD performance. In addition, for multi-fiber modules the overall MD coefficient decreased with increasing packing density, possibly due to flow maldistribution.This study shows that more hydrophobic membranes with a small maximum pore size and higher liquid entry pressure are attainable and favorable for MD applications. In order to enhance MD performance various factors need to be considered to optimize fluid dynamics and module configurations, such as fiber length, packing density and the effect of module diameter and flow rates.

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Membrane Distillation

Khayet

2008

Advanced Membrane Technology and Applications

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Thermal boundary layers in sweeping gas membrane distillation processes

Cited by 74 publications

References 17 publications

Condensation studies in membrane evaporation and sweeping gas membrane distillation

Condensation studies in membrane evaporation and sweeping gas membrane distillation

Performance improvement of PVDF hollow fiber-based membrane distillation process

Membrane Distillation

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