There is a considerable volume of work available in literature which suggests that the performance of axial-flow hollow fibre membrane modules is limited by poorly distributed flow through the shell-side. This study was commissioned to examine the distribution of shell-side flow and its effect on mass transfer and to compare the performance measured by the axial-flow configuration to that obtained by a commonly used alternative known as the helically-wound module design. Laminar flow and mass transfer models have been developed to examine performance through axial-flow hollow fibre modules. These models also consider deviations from laminar flow in the form of turbulence and hydrodynamically undeveloped flow. Modelling analysis on four fibre bundle cross-sections quantify the extent to which channelling limits flow and mass transfer performance. Experimental flow and mass transfer work with locally fabricated hollow fibre modules demonstrated some inconsistencies with axial laminar flow modelling. Pressure drop and mass transfer results exceeded predictions from modelling. This thesis has hypothesised that fibres in axial-flow hollow fibre modules are not aligned as straight and parallel rods (as assumed in modelling) but interweave. Fibre interweaving results in flows between ducts. Such flows create mixing between ducts which results in more intimate contact between the flow and membrane surface, the consequence being higher pressure drop and higher mass transfer. The implication from this work was that axial flow and mass transfer modelling was limited in its use for characterisation of shell-side performance. The experience with helically-wound hollow fibre membrane modules (also fabricated locally) was that, by deliberately inducing flow between ducts, it was possible to considerably improve mass transfer performance. It was found that, whilst helically-wound modules could not be packed as tightly as axial-flow modules and required more sophisticated fabrication techniques, the benefit in their use arose from a substantial improvement in the level of shell-side mass transfer.
| Identifer | oai:union.ndltd.org:ADTP/240721 |
| Date | January 1995 |
| Creators | Costello, Michael John, School of Chemical Engineering & Industrial Chemistry, UNSW |
| Publisher | Awarded by:University of New South Wales. School of Chemical Engineering and Industrial Chemistry |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Michael John Costello, http://unsworks.unsw.edu.au/copyright |
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