MARC 主機 00000nam a2200493K 4500
001 AAI13419727
005 20200623111651.5
006 m o d
007 cr mn ---uuuuu
008 200623s2019 miu sbm 000 0 eng d
020 9780438888852
035 (MiAaPQ)AAI13419727
035 (MiAaPQ)lehigh:12040
040 MiAaPQ|beng|cMiAaPQ|dNTU
100 1 Alshwairekh, Ahmed Mohammed
245 10 Computational Study of Water Desalination Using forward
Osmosis
264 0 |c2019
300 1 online resource (104 pages)
336 text|btxt|2rdacontent
337 computer|bc|2rdamedia
338 online resource|bcr|2rdacarrier
500 Source: Dissertations Abstracts International, Volume: 80-
09, Section: B
500 Publisher info.: Dissertation/Thesis
500 Advisor: Oztekin, Alparslan
502 Thesis (Ph.D.)--Lehigh University, 2019
504 Includes bibliographical references
520 Forward Osmosis is a natural phenomenon that takes places
across a semi-permeable membrane when there is a
concentration difference across the membrane. Pure water
permeates to the highly concentrated channel until the
concentration across the membrane equilibrates. In water
desalination applications, the same principle is applied.
Spiral-wound membrane, flat sheet, or hollow fiber module
are typical configurations in forward osmosis desalination
modules. The application of water desalination using
forward osmosis requires the existence of two channels
separated by a suitable forward osmosis membrane. Sea or
Brackish water is introduced in one side while the other
side has a suitable draw solution. The concentration of
the draw solution must possess several properties for
optimum performance. The vital property is that the draw
solution should have a concentration greater than the sea
or the brackish water. The forward osmosis membrane
consists of an active dense layer and a porous support
layer. The membrane should be designed to have high pure
water permeability with a low solute permeation
coefficient and a low structural parameter. Low values of
the structural parameter ensure that the effect of the
internal dilutive concentration polarization is neglected.
The process of water permeation in a forward osmosis
membrane module has been modeled using computational fluid
dynamic simulations. The local variation of the water flux
along the membrane surface as a function of the local
concentration of both the feed and the draw channels was
calculated. The permeation of the water flux causes the
concentration in the feed channel to increase as the salt
start to accumulate over the membrane surface. While the
concentration of the draw solution is diluted as the water
mixes with the draw solution. In the simulations with a
flat membrane and no mixing promoters, a laminar model was
used. In the model, Navier-Stokes equations along with a
mass transport equation were used to model the flow and
the variation of the concentration inside the channels.
The flow rate was varied to study the effect of the
concentration boundary layer growth in forward osmosis
membrane systems. Also, the thickness of the porous
support layer was varied. The results indicate that
increasing the flow rate indeed improved the water flux by
reducing the growth of the concentration boundary layer.
The presence of the porous support layer drastically
reduces the performance of the system because of the high
level of the internal dilutive concentration polarization
(active layer facing feed solution orientation). It is
important to reduce the thickness of the porous support
layer, increase the porosity or improve the tortuosity of
the porous support layer. The optimum solution is to
remove the porous support layer completely. Corrugating
the membrane should mix the feed and the draw solutions
near the membrane surface. The membrane was corrugated in
a chevron manner. Four different types of corrugations
were considered: (1) a single corrugation where the peak
of the corrugation is towards the feed side to avoid
fouling; (2). a double membrane corrugation so that both
the feed and the draw solutions are mixed; (3) a channel
corrugation in which the membrane is left flat: and (4). a
combined corrugation in which the double and channel
corrugations are combined. In each set of simulations,
three Reynolds number were considered giving twelve sets
of simulations in total. The k - ω SST model is utilized
to characterize the steady state turbulent structures
inside the modules containing corrugations for Re of 300,
800, and 1500. The results indicate that the porous
support layer is still reducing the performance of the
membrane system even with the introduction of the
corrugations. However, there has been improvement in the
water flux up to 15% in the combined corrugation case. The
final part of the dissertation research focused on
removing the effect of the porous support layer and
introducing embedded spacers within the structure of the
membrane. Net-type spacers of 45° and three different
spacer strand diameters are used. The diameters of the
spacer are chosen as 0.1 h, 0.2h, and 0.3h. The flow rate
was changed so that Re is 300, 800, and 1500. The results
indicate that the case with D = 0.3h and Re = 300 had the
best performance
533 Electronic reproduction.|bAnn Arbor, Mich. :|cProQuest,
|d2020
538 Mode of access: World Wide Web
650 4 Engineering
650 4 Mechanical engineering
653 CFD
653 Corrugated
653 Embedded
653 Forward
653 Membrane
653 Osmosis
655 7 Electronic books.|2local
690 0537
690 0548
710 2 ProQuest Information and Learning Co
710 2 Lehigh University.|bMechanical Engineering
773 0 |tDissertations Abstracts International|g80-09B
856 40 |uhttps://pqdd.sinica.edu.tw/twdaoapp/servlet/
advanced?query=13419727|zclick for full text (PQDT)
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