Morphological architecture of dual-layer hollow fiber for membrane distillation with higher desalination performance

Wang, Peng; Teoh, May May; Chung, Tai‐Shung

doi:10.1016/j.watres.2011.08.012

Cited by 175 publications

(115 citation statements)

References 24 publications

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“…In addition, the total active surface area of membrane available is higher in the case of hollow fiber membranes due to both the higher packing density and the individual membrane surface area. Furthermore, as explained by Bonyadi et al [49,50] and Wang et al [269] in their respective papers, the size, shape and connectivity of the macro-voids highly affects water vapor permeation across the membrane. By engineering larger macro-voids connecting the lumen to the membrane wall, Wang et al [269] managed to increase the water vapor permeability up to 98 kg m , making these membranes potential competitors with the commercial best performing FS membranes.…”

Section: Performance Of Organic and Hybrid Membranesmentioning

confidence: 97%

“…As previously described, partial wetting could enhance the chances of low rejection, and work to understand the process behind multi-layer MD membranes and their potential has been conducted [77,259,265]. Although dual layer membranes were mostly processed as HF [127,[265][266][267][268][269], a number of studies also performed similar approaches on flat sheet membranes [263].…”

Section: Hydrophilic/hydrophobic Membranes In Dcmdmentioning

confidence: 99%

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Advances in Membrane Distillation for Water Desalination and Purification Applications

Camacho

Dumée

Zhang

et al. 2013

Water

627

342

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Membrane distillation is a process that utilizes differences in vapor pressure to permeate water through a macro-porous membrane and reject other non-volatile constituents present in the influent water. This review considers the fundamental heat and mass transfer processes in membrane distillation, recent advances in membrane technology, module configurations, and the applications and economics of membrane distillation, and identifies areas that may lead to technological improvements in membrane distillation as well as the application characteristics required for commercial deployment. Keywordsa function of temperature, vapor pressure, and of the gas molecular mass K 0 membrane characteristic defined by Equation (9) Kn Knudsen number K(T) a function of temperature and molecular weight of the gas l mean free path of the molecules l m distance between parallel spacer fibres (m) LEP Limit Entry Pressure (kPa) M molecular mass (g/mol) M w molecular weights of water (g/mol) M a molecular weights of air (g/mol) n number of CNTs per unit cross section in bucky-paper P pressure in the air gap (kPa) half time to reach the maximum intensity-laser flash technique (s) t proportion of conductive heat (balance due to evaporative heat) loss through the membrane T mean temperature in the pores (K)

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Section: Performance Of Organic and Hybrid Membranesmentioning

confidence: 97%

Section: Hydrophilic/hydrophobic Membranes In Dcmdmentioning

confidence: 99%

Advances in Membrane Distillation for Water Desalination and Purification Applications

Camacho

Dumée

Zhang

et al. 2013

Water

627

342

View full text Add to dashboard Cite

show abstract

“…al [14]. Theoretically, the feed concentration should have influence on the permeate flux, and 5% flux variation incurred by the feed concentration was reported [12]. However, there was no detectable flux variation observed in these experiments as the feed changed from deionised water to 1-2 wt% NaCl solution possibly due to the spacer (turbulence promoter) which substantially diminished the concentration boundary layer.…”

Section: Theory and Mathematical Modellingmentioning

confidence: 76%

“…Recently, the membrane fabrication research has achieved continuous breakthroughs due to the efforts of various research groups and the development of new technologies [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Predicting the influence of operating conditions on DCMD flux and thermal efficiency for incompressible and compressible membrane systems

Zhang

Gray

2013

Desalination

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Membrane distillation (MD) is a hybrid of thermal distillation and membrane separation. As a thermal distillation process, MD is an energy intensive technique. Therefore, it is important to select optimum operation parameters to maximise both the flux and energy efficiency, even though low grade or waste heat maybe employed in the process. In this paper, a model originally developed for Direct Contact Membrane Distillation (DCMD) using a compressible membrane is employed to predict the thermal efficiency and flux for both compressible and incompressible membrane systems. The predicted thermal efficiency was also compared with experimental results, and the errors were mostly within the range of experimental variation (±5%). As a result of membrane compressibility, the thermal conductivity and vapour permeability of the membrane were altered, causing a change in flux and energy efficiency. If a compressible membrane is used, it was found from the predicted results, that increasing stream velocity will reduce the thermal efficiency and even reduce flux once the increased pressure associated with the higher flows is in the range to compress the membrane. Increasing temperature either on feed side or on permeate side will increase thermal efficiency. In scaling up the process using a compressible membrane, it is necessary to reduce the pressure drop across the module in the DCMD process to maximise energy efficiency and flux. Since the operating temperature is normally not adjustable when low grade waste heat is employed, optimising the flowrates and pressure drops are the key factors for optimising flux and thermal efficiency.

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“…Surging interest in MD membrane development has been seen in laboratory and industry recently, though there exist only a few highly-permeable membranes [3,4]. On the other hand, much effort has been devoted to the MD process in order to mitigate the TP effect and further increase permeation flux [5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Analysis of heat and mass transfer by CFD for performance enhancement in direct contact membrane distillation

Yu¹,

Yang²,

Wang³

et al. 2012

Journal of Membrane Science

132

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A comprehensive analysis on the dominant effects for heat and mass transfer in the direct contact membrane distillation (DCMD) process has been performed with the aid of computational fluid dynamics (CFD) simulations for hollow fiber modules without and with annular baffles attached to the shell wall. Potential enhancement strategies under different circumstances have been investigated. Numerical simulations were carried out to investigate the effect of the MD intrinsic mass-transfer coefficient of the membrane (C) on the performance enhancement for both non-baffled and baffled modules. It was found that the temperature polarization coefficient (TPC) decreases significantly with increasing C value regardless of the existence of baffles, signifying a loss of overall driving force. However, the higher C compensated for this and the mass flux showed an increasing trend. A membrane with a lower C value was found to be less vulnerable to the TP effect. In this case, the introduction of turbulence aids such as baffles did not show substantial effect to improve system performance. In contrast, introducing baffles into the module can greatly enhance the mass flux and the TPC for a membrane with a high C value, where the main heat-transfer resistance is determined by the fluid side boundary layers.The effect of operating temperature on heat and mass transfer in the MD process was also studied with a membrane of a lower C value (2.0×10 -7 kg·m -2 ·s -1 ·Pa -1 ). Although the TPC generally decreased with increasing operating temperatures, the mass flux N m increased significantly when operating temperature increased. A baffled module showed a more significant improvement than a non-baffle module at a higher temperature. Moreover, it was confirmed that higher operating temperatures are preferable for a substantial improvement in the heat/mass transfer as well as MD thermal efficiency, even with a relatively small transmembrane temperature difference of 10K.

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Morphological architecture of dual-layer hollow fiber for membrane distillation with higher desalination performance

Cited by 175 publications

References 24 publications

Advances in Membrane Distillation for Water Desalination and Purification Applications

Advances in Membrane Distillation for Water Desalination and Purification Applications

Predicting the influence of operating conditions on DCMD flux and thermal efficiency for incompressible and compressible membrane systems

Analysis of heat and mass transfer by CFD for performance enhancement in direct contact membrane distillation

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