Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The hydrodynamics of a hollow fibre membrane module for the ultrafiltration of
potable water were investigated. The purpose was to use a hydrodynamic model to
predict the permeate flux for modules of various dimensions. Various models were
considered, but most of them could not account for important effects such as
macroscopic radial gradients and wet fibre expansion, found in hollow-fibre
membrane modules. The Porous Medium Model was found to be a suitable model
and it was used together with a finite element software package, Fastflo, to solve for
the pressure distributions inside the membrane modules and predict permeate flux.
The permeability of the membranes was obtained using a combination of numerical
and experimental procedures and was found to be 2.3 x 10-13m. A cost analysis was
performed to find the most economical module dimensions (outer diameter and
length) for any required product flow rate. It was assumed that the cost of the fibres
and module housing comprised the capital cost, while the operating cost consisted of
the pumping energy. A capital recovery factor of 0.3 was used to convert capital
costs to a yearly cost. It was found that the optimum module dimensions are an
outer diameter of between 90mm and 160mm and a length of 0.6m. Finally the
pressure distributions on the lumen and shell sides during both cross-flow filtration
and backwash were examined. Shade plots proved useful for identifying possible
areas of stagnant flow, as well as indicating where backwash is the most effective. / AFRIKAANSE OPSOMMING: Die hidrodinamika binne-in 'n holvesel membraanmodule vir die ultrafiltrasie van
drinkwater is ondersoek. Die doel was om 'n hidrodinamiese model te gebruik om
die permeaatvloed vir modules van verskeie dimensies te voorspel. Verskillende
modelle is oorweeg, maar die meeste kon nie belangrike faktore soos makroskopiese
radiale drukqradiente of nat veselverlenging in ag neem nie. Die Poreuse Medium
Model was die mees geskikte model en is gebruik saam met Fastf/o, 'n sagteware
pakket wat gegrond is op die eindige element metode, om vergelykings vir die
drukverspreiding binne-in die module op te los en permeaatvloed te voorspel. Die
permeabiliteit van die membrane is verkry met behulp van numeriese en
eksperimentele prosedures en 'n waarde van 2.3 x 10-13 m is bepaal. Hierna is 'n
koste-analise uitgevoer om die mees ekonomiese module afmetings (Iengte en buitedeursnit)
te bepaal vir 'n gegewe produk vloeitempo. Daar is aanvaar dat
kapitaalkoste bestaan uit die koste van vesels en module-omhulsel, terwyl
bedryfskoste bereken is deur die hoeveelheid energie benodig om die pomp aan te
dryf. 'n Kapitaalherwinningsfaktor van 0.3 is gebruik om kapitaalkoste om te skakel
na 'n jaarlikse koste. Die optimum module afmetings is 'n lengte van 0.6m en 'n
buite-deursnit van tussen 90mm en 160mm. Laastens is die drukverspreidings
tydens beide kruisvloeifiltrasie en die terugspoelproses ondersoek. Areas van
stagnante vloei kan deur middel van skadu-grafieke geYdentifiseer word, terwyl dit
ook moontlik is om die terugspoelproses te optimeer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52531 |
| Date | 12 1900 |
| Creators | Marais, Pierre Charl |
| Contributors | Bradshaw, S. M., Jacobs, E. P., Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 141 p. : ill. |
| Rights | Stellenbosch University |
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